Staphylococcus – Gram + cocci Arranged in Bunches of Grapes – produce Catalase (protection against killing by Neutrophil) Staphylococcus aureus • Coagulase +, ferments Mannitol, β-Haemolytic • Surface components:

o Protein A – pathogenicity factor in cell wall, binds to Fc portion of IgG to prevent binding & activation of complement

o Teichoic Acids – adherence to mucosal cells o Microcapsule – antiphagocytic o Peptidoglycan – endotoxin-like properties (stimulate

production of cytokines and activate complement and coagulase cascades (can manifest as septic shock)

• Transmission: in Vagina of 5% of women, human lesions o NF to anterior nares, nasopharynx, and axilla

• Pathogenesis: o Enterotoxins A-F – acts as a Superantigen within GIT,

releasing lots of IL-1 & 2, causing food poisoning o Toxic Shock Syndrome Toxin (TSST) – produced in Vagina,

Nose, or other infected site acts as a Superantigen releasing IL-1, IL-2 & TNF

Tx: administer fluids, pressor drugs and inotropic drugs to ↑BP, beta-lactamase-resistant drugs (Nafcillin), serum globulins containing anti-TSST antibodies may be useful in neutralizing toxin

o Exfoliatin – cleaves Desmoglein causing separation of epidermis at Granular cell layer (stratum granulosum) desquamation of the skin = Scaled Skin Syndrome (fever, large bullae, electrolyte imbalance)

o Enzymes – coagulase, fibrinolysin, hyaluronidase, proteases, nucleases, lipases, cytolytic enzymes (lyse any cell causing marked necrosis of skin and haemolysis)

Coagulase – “walls off” infection site by clotting plasma

Fibrinolysin – lyse thrombi

Hyaluronidase helps with movement/spread of infection through connective tissue

• Clinical findings: o Skin Infections – Impetigo*, furuncles, carbuncles, cellulites,

folliculitis, blepharitis, mastitis o Septicaemia – active division of the organism within the

bloodstream followed by colonization causes Fever, Purpura, DIC (may lead to formation of metastatic abscesses)

o Infective Endocarditis – infects normal heart valves & IV drug abusers (right-sided endocarditis MC bc IV drug users inject into veins RA/RV)

Sudden onset of fever, heart murmur*, and leukocytosis

o Osteomyelitis & Arthritis – esp in Children; hematogenous spread; children with bone/joint pain, limp/gait abnormality

o Pneumonia – in postoperative patients (MC nosocomial pneumonia) following viral infection possible abscess formation and empyema

o Food Poisoning – more vomiting than diarrhea, short incubation period (4-8 hrs), pre-formed toxin within protein rich food (custard, eggs, ham, chocolate)

o TSS – Fever, Hypotension*, sunburn-like rash (maculopapular) that desquamates, involvement of 3 or more of Liver, Kidney, GIT, CNS, muscle, blood (no labs needed)

• Lab diagnosis: golden-yellow colonies, β-haemolytic (clear haemolysis), Mannitol-Salt agar

• Treatment: Penicillins, Cephalosporons (inhibit cell wall synthesis - β-lactams) – bind PBP on bacteria (if modified = no binding and no cell wall synthesis inhibition) o 90% of strains are resistant to Penicillin due to plasmid

containing beta-lactamase o 20% of strains are methicillin-resistant (MRSA) or nafcillin-

resistant (NRSA) DOC then is vancomycin + gentamicin o Synercid – investigational drug currently o Abscesses – requires drainage (mastitis, septic arthritis)

Staphylococcus epidermidis • Coagulase -, Non-Haemolytic

• Diseases: usually hospital-acquired Endocarditis, Prosthetic joint infections

• Pathogenesis: pyogenic infection by eliciting Neutrophilic response o Glycocalyx (biofilm) for adherence

• Clinical findings: infections of IV catheters & prosthetic implants o neonatal sepsis, peritonitis (peritoneal dialysis due to kidney

failure) & cerebrospinal shunts (hydrocephalus) • Laboratory diagnosis: white colonies, non-haemolytic,

Novobiocin-sensitive (zone of growth inhibition) • Treatment: highly antibiotic-resistant, most produce beta-

lactamase, methicillin and nafcillin resistant o Vancomycin (DOC) with rifampin or AG o Remove catheter or other prosthetic device

Staphylococcus saprophyticus • Coagulase -, Non-Haemolytic • Pathogenesis: pyogenic infection by eliciting Neutrophilic

response • Clinical findings: community-acquired, 2nd most common cause

of UTIs after E. coli (Gm -) o Dysuria, ↑ urinary frequency, no fever, burning o Staph sap. can reduce nitrates nitrites (E. coli cannot)

• Laboratory diagnosis: white colonies, non-haemolytic, Novobiocin-insensitive

• Treatment: Quinolone (inhibit topoisomerase or DNA gyrase) or Trimethoprim-sulfamethoxazole (inhibit folic acid synthesis)

Streptococcus – Gram + cocci Arranged in chains or pairs – Catalase negative (no protection from neutrophil killing/phagocytosis) α-hemolysis = green zone formed around colonies on blood agar due to Incomplete lysis β-hemolysis = clear zone formed around colonies on blood agar due to Complete lysis by Streptolysins O & S

• C Carbohydrate – in cell wall, used to determine “group” of β-hemolytic streptococcus (ex. A, B, etc) – determined by amino sugar o Lancefield groups – groups A-U identification carried out

by precipitin tests • M Protein – anti-phagocytic virulence factor protruding from cell

surface and interferes with ingestion by phagocytes, determines “serotype” of group A (S. pyogenes) [~80 serotypes = multiple strep pyogenes infections] γ-hemolysis = non-hemolytic • Groups can be grouped into those that cause primarily

rheumatic fever and those that cause primarily nephritogenic (strain 12) on basis of M-protein

Streptococcus pyogenes • β-hemolysis – Group A – Bacitracin sensitive –

Antiphagocytic hyaluronic acid capsule • M-protein: major virulence factor (fimbriae for adherence to

pharyngeal epithelium) – further serotyping • Pathogenesis:

o Pyogenic Inflammation – locally at site of multiplication in tissues Pharyngitis, cellulitis

o Exotoxin Production (toxigenic) – cause systemic symptoms where organisms are not present Scarlet fever (blanching rash), Toxic-shock-like syndrome (TSLS)

o Immunological Damage – cross-reaction of Ab (antigens/normal tissue share epitopes = autoimmune) against component of bacterium to normal tissue resulting in inflammation Rheumatic fever, acute Glomerulonephritis

o Enzymes –DNase = Streptodornase (reduce viscosity of pus – antibodies to DNase B develop during pyoderma), Hyaluronidase (spreading factor), Streptokinase (fibrolysin – activates plasminogen to dissolve clots)

o Erythrogenic/Pyrogenic Toxin – causes rash of Scarlet fever (difficult swallowing, sore throat + rash), SUPERANTIGEN, necessary to have Phage carrying the gene for the toxin (lysogenized strains)

o Streptolysin O – antigenic, ASO (Ab) titer (>200) can be diagnostic in Rheumatic Fever (mitral stenosis), oxygen-labile

o Streptolysin S – non-antigenic, non-oxygen-labile beta-haemolysis

o Pyrogenic Exotoxin A – causes most cases of TSLS, SUPERANTIGEN

o Exotoxin B – rapidly destroys tissue necrotizing fasciitis (flesh-eating bacteria)

• Clinical findings: o Pharyngitis* (MC bacterial sore throat) – spontaneous

recovery within 10 days, OR may extend to Otitis, Sinusitis, Mastoiditis or Meningitis, Rheumatic fever (non-suppurative infection, auto-Ab), Scarlet fever (w/ Erythrogenic)

Sore throat, difficulty in swallowing, lymphadenopathy, tender cervical LN, fever

o Scarlet fever – diffuse erythematous blanching rash, followed by desquamation (5-7 days); buccal mucosa is deep red except for circum-oral pallor around mouth & nose, palms and soles, punctate hemorrhages on hard/soft palates, yellow-white exudates later sheds to reveal Strawberry tongue

o Streptococcal toxic shock syndrome (TSLS) – similar clinical findings to Staph.

o Skin infections* – cellulitis, pyoderma (Impetigo – pus-filled lesions honey-crusted), erysipelas

D/D: Staph (catalase +) o Other – Necrotising fasciitis, Lymphangitis (red lymphatics,

streaks), bacteraemia, Puerperal fever (vaginal infection ascends into endometrium [endometritis] after childbirth), Glomerulonephritis (non-suppurative infection, follows after skin infections like pyoderma), Rheumatic Fever (follows a sore throat)

• Post-streptococcal diseases: o Acute Glomerulonephritis (AGN) – child - 2-3 weeks after

skin infection, Ag-Ab complexes (medium-sized) on glomerular basement membrane (activate complement, recruit neutrophils, Type III hypersensitivty – lose integrity

of BM hematuria/proteinuria), HTN, edema, “Smoky” urine = M12 Strain

Early eradication of nephritogenic strep at sites of colonization in skin diseases

o Acute Rheumatic Fever – 2 weeks after pharyngitis (NOT skin infections!), cross-reaction Ab btw certain serotypes of M protein & antigens of Joint & Heart tissue (Type II Hypersensitivity), Migratory Polyarthritis, Pancarditis (involvement of all layers-valves murmur Mitral Stenosis), ASO titers elevated (>200), ↑ESR

o Tx for Group A – Penicillin G (no benefit if symptoms of rheumatic fever or AGN have begun), oral penicillin V used to treat mild infections, allergic to penicillin erythromycin

o Prevention - Benzathine (long acting penicillin given to prevent recurrence of rheumatic fever)

Streptococcus agalactiae • β-hemolysis – Group B – Bacitracin resistant – hydrolyse

Hippurate – polysaccharide Capsule • Transmission: NF of Colon, genital tract of some women

(infection to newborn thru birth canal = sepsis or meningitis) • Pathogenesis: do NOT produce cytotoxic enzymes or exotoxins –

elicits Inflammatory response • Clinical findings:

o Neonatal sepsis & meningitis (#1 cause in neonate) – due to colonization of mother’s vaginal epithelium, Rupture of Membranes >18 hrs prior to delivery, premature birth (<37 gestation), mother lacking Abs to group B – also causes Neonatal Pneumonia (aspiration)

Signs of Meningitis – failure to feed, difficult to arouse the baby, restlessness/irritability, nuccal rigidity confirm with CSF analysis (gram stain) – gram (+) chains Strep, gram (-) E coli, gram (+) rod Listeria

CSF findings – high levels of PMN’s (10-20,000), organisms present, ↓glucose

o Adults: Pneumonia, Endocarditis, arthritis, Osteomyelitis, post-partum endometritis, DM predisposes to infection

• Diagnosis: CAMP test – enhanced hemolysis when combined w/ β-hemolysin of Staph. Aureus

• Tx – Penicillin G or Ampicillin Enterococcus faecalis & faecium • β-hemolysis – Group D – grows in 6.5% Saline and presence

of bile – hydrolyze Esculin black pigment • Clinical findings: NF of colon

o UTI – predisposed by indwelling Urinary Catheters (hospital-acquired) reduces nitrates to nitrites

o Endocarditis – predisposed by GI & UT surgery/instrumentation (prophylactic with ampicillin and gentamycin)

o Tx - Resistance to Penicillin G, combination with AG required – E. faecium is vancomycin-resistant

Streptococcus bovis • β-hemolysis – Group D – 6.5% Saline sensitive - hydrolyze

Esculin black pigment • Clinical findings:

o Endocarditis – predisposed by Carcinoma of the Colon Viridans streptococci • α-hemolysis – non-Bile-soluble – Optochin resistant • Diseases: Subacute Infective Endocarditis • Transmission: normal flora of Pharynx (S. mitis, S. sanguis, S.

mutans) • Pathogenesis:

o Forms Biofilms (Dextran – S. mutans) to mediate adherence onto Teeth or damaged Heart Valves

• Clinical findings: o Sub-Acute Infective Endocarditis – enter bloodstream

(hematogenous spread) from Oropharynx after Dental Surgery, fever, Splinter hemorrhages (dislodged platelet/fibrin thrombi), Janeway lesions/Oslers nodes, heart murmur, slow progression so will see signs/symptoms (*Attacks previously damaged heart valves)

o Brain/Abdominal/Lung/Pelvic abscesses – often mixed infections with mouth anaerobes – Peptostreptococci (dental surgery is predisposing) – homeless, alcoholics, poor hygiene

• Diagnosis: alpha-hemolysis, not lysed by bile, grows in Optochin (P disc)

• Tx – prolonged Penicillin • Prevention – amoxicillin given before dental surgery Streptococcus pneumoniae • Lancet-shaped in pairs or chains • α-hemolysis – Bile-soluble – Optochin (P-disc) sensitive –

antiphagocytic polysaccharide Capsule • Diseases: most infections in LUNG MOPS

o MC community-acquired Pneumonia Multiply in tissues causing inflammation – when

reach alveoli cause outpouring of fluid, RBCs & WBCs consolidation of lung phagocytosed during recovery and mononuclear cells ingest debris = resolve consolidation

Clinical Features - Sudden fever, cough, chills, pleuritic pain with productive cough of “rusty” sputum, dullness on percussion, diminished breath sounds bacteraemia in 15-25% of cases Spontaneous recovery can begin after 5-10 days, accompanied by development of anti-capsular Abs

Predisposing factors – abnormal cough reflex, can’t rid of aspirations/secretions, *viral resp. infection, bronchial obstruction or injury, abnormal circulatory dynamics, *splenectomy, *sickle cell anemia or nephrosis

o Meningitis – 3 months-2y/o and vaccinated (Haemophilus in non-vaccinated), head trauma resulting in rhinorrhea, Elderly 65 y/o

o Bacteraemia in splenectomized patients o Otitis media & chronic sinusitis

• Diagnosis: sputum smears, Quelling reaction, CSF assay • Transmission: present in Oropharynx of healthy population • Quelling Reaction used to identify serotype – swelling of capsule

in presence of homologous antibody (LPA – latex particle agglutination)

• Pathogenesis: o Capsule – most important virulence factor, Abs are protective

o C wall carbohydrate reacts with CRP (synthesized in liver it’s an acute phase protein, ↑1000-fold in acute non-specific inflammation)

Elevated CRP also good predictor of MI (compared to cholesterol)

o **IgA Protease – enhances ability to colonize mucosa of URT

o Teichoic acid & Peptidoglycan – chemoattractant, activates complement & cytokine production Septic Shock in immunocompromised

o Pneumolysin – responsible for alpha-hemolysis • Prevention: Vaccine (Pneumovax) against 23 serotypes elderly

and Splenectomized patients, 7 serotypes for children – vaccine tagged with a toxoid (conjugated)

• Tx – Penicillin or erythromycin, vancomycin Peptostreptococci

• Anerobes or microaerophiles • Variable hemolysis NF of gut, mouth and female genital tract • Participate in mixed anaerobic infections – brain abscesses after

dental surgery Neisseria – Gram – cocci (pink on gram stain), non-motile, non-spore forming, non acid-fast Arranged in “Kidney Bean” pairs – Oxidase positive (cytochrome C) – grows on Chocolate or Thayer agar Endotoxin in Outer Membrane, readily phagocytosed by PMNs (*picture) Neisseria meningitidis • LPS endotoxin – polysaccharide Capsule – ferments Maltose &

Glucose • Transmission: Airborne droplets, colonize Nasopharynx where it

can enter bloodstream, common in Dorms or Military • Pathogenesis:

o Capsule - resists phagocytosis by PMNs o LPS Endotoxin – fever & septic shock o IgA Protease – aids in Attachment to membranes of URT by

cleaving IgA

o C6-C9 Deficiencies – increased risk of meningococcal Bacteraemia

• Clinical findings: o Meningococcemia – septicemia with Neisseria, seeding of

many organs, especially meninges o Meningococcal Meningitis – MC in 2-18 y/o (young

adults/adolescence) - fever, headache, stiff neck, increased PMNs in CSF

o Waterhouse-Friderichson syndrome – life-threatening meningococcemia characterized by high fever, shock, widespread Purpuric Rash, DIC, Adrenal Insufficiency

o CSF – elevation in Neutrophils & Protein, decrease in Glucose

o Tx – Cephalosporons: • Diagnosis – smear and culture of blood and spinal fluid; D/D w/

N. gonorrhoeae (can’y ferment maltose) • Vaccine Neisseria gonorrhoeae • LOS (lipo-oligosaccharide) endotoxin – NO capsule – Pilus

protein Ag variation (chromosomal rearrangement) – ferments Glucose – killed by Cold & Dry

• Transmission: sexually & vertically during birth, moist environments (2nd MC STD)

• Pathogenesis: o Pili – mediates attachment to Mucosal surfaces,

antiphagocytic, virulent o LOS – less toxic than LPS o IgA Protease – hydrolyzes secretory IgA allowing attachment

to mucosa o Outer membrane proteins I, II, III Protein II important in

attachment to host cells • Host Defense – IgA and IgG, complement, and neutrophils

(phagocytosis) o Repeated infection due to antigenic changes in pili protein

and outer membrane proteins • Clinical findings:

o Men – Gonococcal Urethritis dysuria, epididymitis & purulent Discharge

o Women – Cervicitis PID due to recurrent infections (fever, adnexal tenderness, lower abdominal pain), Tubo-ovarian mass fibrosis leading to infertility or ectopic pregnancy

o Can disseminate: arthritis, tenosynovitis, and pustules in skin (septic arthritis in sexually active adult)

o Anorectal infections – often asymptomatic, or Proctitis (bloody or purulent discharge)

o Neonatal Conjunctivitis – ophthalmia neonatorum during passage through birth canal prophylactic use of Erythromycin or Silver Nitrate eye ointment

• Diagnosis – organisms w/in PMN (male urethra discharge), cervical specimen (NF also diplococci gram (-) – NOT very diagnostic) so use DNA probes/Elisa (rapid test), Thayer-Martin agar

• Tx – DOC Ceftriaxone, resistance due to plasmids Bacillus – Gram + rods Aerobic – Spore forming Bacillus anthracis • Square-ended “Boxcar” chains – anti-phagocytic Poly-D-

Glutamate Capsule • Transmission: soil contamination/skinning animals of wound –

Cutaneous or Pulmonary (inhaled spores – football field), Gastro anthrax (contaminated meat)

• Risk: occupational contact w Animal Hides • Pathogenesis:

o Anthrax Toxin – Edema (activates Adenylate Cyclase = ↑cAMP = loss of fluid), Lethal (inhibits Phosphorylation – cleaves phosphokinase that activates MAPK signal transduction pathway = no cell growth) & Protective (pore formation mediates entry of edema and lethal factor)

• Clinical findings: o Cutaneous* – occupational setting: typical lesion - malignant

pustule, local edema, painless ulcer w/ Black Eschar If untreated progresses to bacteraemia

o Pulmonary* – non-specific respiratory symptoms; hemorrhagic mediastinitis (hilar LN) & widening (many

people w/ same symptoms), bloody pleural effusion, hemorrhagic meningitis complication, septic shock and death

o Gastrointestinal – vomiting, abdominal pain, bloody diarrhea • Diagnosis – smear, ELISA for antibodies to the toxin • Tx - DOC Penicillin G, Ciprofloxacin for prophylactics (targets

DNA gyrase), vaccine for individuals in high risk regions/occupations

Bacillus cereus • Transmission: Endospores in Fried Rice survive boiling & grow

if kept warm portal of entry is GIT • Pathogenesis:

o Cholera-like Enterotoxin – increases cAMP efflux of water & Cl-

o Staphylococcus-like Enterotoxin – acts as a superantigen w/in enteric tract

• Clinical findings: o Staph-like – Short incubation period (4 hrs), mostly nausea &

vomiting o Clostridium-like – Longer incubation period (16-18 hs),

watery & non-bloody diarrhea • Tx - symptomatic Clostridium – Gram + rods Anaerobic – Spore forming Clostridium tetanii • “Tennis-racket” shape w/ terminal spore, drumstick • Transmission: in Soil, traumatic breaks in skin or crush injury,

Skin-popping in IV drug abusers, via Contaminated Umbilicus in neonates

• Endospore Germination – favored by necrotic tissue, poor blood supply to wound *Wound management to prevent*

• Pathogenesis: o *Tetanus Toxin – produced by Vegetative cells at wound site,

travels Intra-Axonally to CNS, binds Ganglioside receptors, blocks release of Glycine & GABA muscle spasm

• Clinical findings: Vignette – can’t acquire vaccination records of patient

o Tetany – Spastic Paralysis, lock jaw (Trismus), grimace (Risus Sardonicus), exaggerated reflexes, arching of back (Opisthotonos), RESPIRATORY FAILURE

o Neonatal Tetanus – woman not vaccinated (developing countries), delivery in home/elevator and use dirty knife/scissors to cut umbilical cord

• Prevention: DTP vaccine (diphtheria, tetanus, pertussis toxoid – retain antigenicity), Toxoid booster should be given ever 10 years, Immunoglobulin can be given along with Toxoid booster for Passive-Active immunity (big contamination), Patient with tetanus-prone wound Vaccine + TIG if not completed primary series, just vaccine if completed primary series

• Diagnosis – clinical examination, organism rarely isolated • Tx – hyper-immune human globulin to neutralize the toxin

(passive immunity), Penicillin G or Metronidazole* (DOC for many anaerobic infections), spasmolytic drugs (BZD – Valium)

Clostridium botulinum Anaerobic, spore-forming rod • Transmission: in Soil, vegetables, meat, Honey, alkaline foods -

Canned food & Smoked fish • Pathogenesis:

o *Botulinum Toxin – protease cleaves proteins involved in release of ACh at neuromuscular junctions, encoded by lysogenized phage, results in Flaccid Paralysis (hypotonia, LMN lesion-like) – diluted toxin = Botox

• Clinical findings: o Descending muscle weakness and paralysis, diplopia (double

vision), pharyngeal and laryngeal muscles (dysphagia), risk for RESPIRATORY FAILURE

o Wound Botulism – spores contaminate wound and germinate (associated with drug abuse, skin popping, black tar heroin)

o Adult Botulism – Preformed toxin in canned food, descending weakness & paralysis, Respiratory Failure

o Infant Botulism – ingestion of contaminated Honey (actual spores) can introduce C. botulinum into the gut where it grows & produces toxin (not enough NF) weakness & respiratory distress (floppy baby – limp), but recover spontaneously

• Diagnosis – presence of toxin in serum*, stool or food – blood/stool culture not as sensitive

• Tx – Trivalent antitoxin (made from horse serum) Clostridium perfringens • Transmission: in Soil, Colon & Vagina normal flora, trauma

(crush injury) • Pathogenesis:

o Gas Gangrene – contamination of wound w Soil or Feces, Lecithinase* (α-Toxin - cytolytic) cleaves cell membranes, leads to hemolysis, myonecrosis (D/D: Strep pyogens for flesh-eating bacteria)

Production of gas in tissue pain, edema and cellulitis

Lyses of blood cells hemolysis, jaundice, blood-tinged exudates

o Food Poisoning – ingestion of preformed spores in Reheated Meat dishes (Mexican food), Enterotoxin released & acts as a Superantigen (longer incubation than Staph. aureus)

• Clinical findings: o Gas Gangrene (myonecrosis) – Crepitation indicates presence

of gas under pressure in tissues, jaundice from hemolysis of RBCs, septic abortion

o Food Poisoning – ingests spores that produce enterotoxin (Staph-like) watery diarrhea resolves in 24 hrs

• Lab Diagnosis: Double ring of hemolysis on blood agar, Nagler’s reaction coats half the plate w/ Antitoxin to alpha-toxin

• Tx – Penicillin G, clean wound, possible amputation (Risk – DM: peripheral arteriole disease, peripheral neuropathy)

Clostridium difficile • Transmission: Colon normal flora, Most common cause of

Nosocomial Diarrhea • Pathogenesis:

o Antibiotic Therapy – suppression of normal flora causes overgrowth within Intestine, produces a lot of Exotoxins A & B: disrupts Actin polymerization, membrane damage, loss of cytoskeletal integrity apoptosis of enterocytes

• Clinical findings:

o Antibiotic-associated Pseudo-membranous colitis – membrane on top of colonic mucosa - plaque, can invade/inflammation non-bloody diarrhea with neutrophils present in stool (toxic megacolon may occur due to lack of myenteric/aurebach plexus)

Clindamycin, broad-spectrum antibiotic, chemotherapy

• Diagnosis: exotoxin in stool by cytopathic effect on cultured cells, ELISA (less sensitive) clean bed-pan by autoclaving to kill spores

• Tx – Metronidazole and withdrawal causative antibiotic (Vancomycin can be used)

Cornyebacterium – Gram + rods Aerobic – Non-spore forming – club-shaped/beaded appearance Corynebacterium diphtheriae • Club-shaped, arranged in V or L shape, beaded

Metachromatically-staining appearance (Volutin) – polymerized phosphates

• Transmission: Throat normal flora, respiratory droplets • Pathogenesis: toxigenic and non-toxigenic strains

o Diphtheria Toxin – exotoxin prevents EF-2 protein synthesis (ADP-ribosylation), has AB structure (B facilitates entry), encoded by Phage (lysogenized) O.B.E.D. (botulism, enterotoxin (Scarlet fever), diptheria)

• Clinical findings: o Grey membrane - pseudomembranes on tonsils in throat

airway obstruction o Fever, sore throat, “Bull-neck” due to involvement of

Cervical LNs o Cranial Nerve weakness or paralysis (muscles of soft palate

and pharynx) o Hemorrhage when hit the membrane on examination o Myocarditis – arrhythmias and circulatory collapse

• Lab: isolate organism or demonstrate toxin production o Loeffler’s medium shows Black colonies due to reduction of

Tellurite Tellurium o PCR to detect toxin gene

• Prevention – DPT toxoid vaccine, boosters every 10 yrs Listeria – Gram + rods Non-spore forming – Tumbling motility – Facultative Intracellular Listeria monocytogenes • Arranged in V or L shape • Aerobic – narrow zone of β-hemolysis – Cold growth • Transmission: Animals (unpasteurized milk [cheese or goat’s

milk] & undercooked meat), plants (cabbage), soil, GI & female genital tract NF

• Pathogenesis: o Vertical – via Placenta or during Delivery o Immunosuppressed – Renal Transplant patients o Actin “Rockets” – moves btw cells when Actin contracts &

propels the bacterium through membranes of Mononuclear Phagocytic cells (macrophages – intracellular pathogen) need T-cell mediated immunity = granulomas

o Listeriolysin O – hemolytic and cytolytic = degrades cell membrane

• Clinical findings: o Meningitis & Sepsis in newborns – can lead to abortion,

premature delivery or peripartum sepsis, chorioamnioitis – granulomas at birth

o Febrile Gastroenteritis – watery diarrhea & little vomiting, fever, headache, myalgia, abdominal cramps

• Diagnosis – isolate, tumbling motility, small hemolytic colonies • Tx - Ampicillin Immunology Myeloid = Granulocytic (neutrophil, basophil, eosinophil) & Monocytic (macrophage, kupffer, dendritic) Lymphoid = T-cell, B-cell & NK cell (bridge btwn innate and adaptive) Innate Immune System: first line of defense against invading organisms – NON-SPECIFIC

o Cellular components: granulocytes and monocytes

o Humoral components: complement o Anatomical features that function as barriers (skin, epithelia,

mucosa) • Mucins, ciliary movement (lost in CF), peristalsis, • Flushing action of tears/saliva

- Lysozyme and phospholipase A (break-down membranes)

- Histidine-rich peptides in saliva • Acidic pH of stomach, digestive enzymes, bile salts

and fatty acids • Alpha-defensins made by panneth cells, Beta-

defensins made in respiratory and urinary tracts • Normal flora (compete for nutrients so as to ↓growth

of pathogens) o Acute inflammation mediated by complement

characterized by edema and phagocytic cells-PMN (increased vascular permeability, recruitment of phagocytic cells, opsonization (C3b, IgG), and lysis of bacteria

o Coagulative system – lactoferrin and transferring (limit iron availability limiting bacterial growth)

o Interferons, Lysozyme, and Interleukins o Not antigen specific or dependent o There is immediate maximal response o Exposure results in no immunological memory

Phagocytosis • Phagocytes have a variety of receptors

o Fc receptors – bacteria with IgG antibody on their surface have the Fc region exposed which binds to the receptor on phagocytes

o Complement receptors – C3b-coated bacteria bind resulting in enhanced phagocytosis

o Scavenger receptors – bind a variety of polyanions on bacterial surfaces

o Toll-like Receptors (Pattern Recognition Receptors) – recognize & bind Pathogen Associated Molecular Patterns (PAMPs) on infectious agents Phagocytosis & release of Cytokines (IL-1, TNF, IL-6) by the phagocytes

• Macrophages & then Neutrophils are the first cells to encounter pathogens

• Respiratory Burst – Superoxide anion & Hydrogen Peroxide are directly toxic – Hypochlorite & Hydroxyl free radicals are generated from Hydrogen Peroxide o HMP-shunt NADPH Oxidase = Respiratory Burst o Chronic Granulomatous Disease patients do not produce

respiratory burst (NADPH Oxidase Deficiency) • NO Killing - Binding to TLRs results in production of TNF-α

induce expression of NO Synthetase gene production of NO – If cell is exposed to IFN-γ produces additional NO

NK cells – large granular lymphocytes that have cytotoxic ctivity o Kill virus-infected and tumor cells o NKR – receptor promotes killing

• Virus infected and tumor cells have missing or changed MHC class 1 molecule that cannot stimulate negative signal triggers killing

o KIR – receptor inhibits killing • KIR binds to self MHC class 1 molecules on target

cells inhibiting killing of self cells Adaptive Immune System: second line of defense that affords protection against re-exposure to the same pathogen

o Cellular components: lymphocytes – T cells – CD4 and CD8 lyse infected cells (intracellular antigens = virus)

o Humoral component: B cells plasma cells and production of antibodies for extracellular antigens

o SPECIFICITY, DIVERSITY, MEMORY • Response is antigen dependent and antigen specific • Deal with a variety of pathogens during lifetime • Lag time between exposure and response • Results in immunological memory (↓lag phase on

next exposure) o B-cells recognize antigens via surface receptor (BCR) =

immunoglobulin (once encountered they transform into plasma cells that secrete antibodies)

o T-cells recognize antigens via TCR and carry out effector functions by producing cytokines (IL-1)

o Clonal Selection – each lymphocyte bears a single type of receptor with a unique specificity interaction btwn a foreign molecule and a lymphocyte receptor capable of binding that molecule with high affinity leads to lymphocyte activation

• All cells derived from an activated lymphocyte will bear receptors of identical specificity

• Lymphocytes bearing receptors specific for self molecules are deleted at an early stage (prevent auto-immunity)

Cells of Immune System • Monocyte: kidney-shaped nucleus found in bloodstream

differentiates into macrophage in tissue for phagocytosis and secretion of cytokines

• Dendritic cell (antigen-presenting cell): located in epithelia and tissues, long cytoplasmic arms

• Neutrophil (polymorphonuclear leukocyte): multilobed nucleus (3-5 segments) and large pink granules phagocytosis and activation of bacterial mechanisms

• Eosinophil: bilobed nucleus with large pink granules killing of antibody-coated parasites (IgE)

• Basophil: myeloid bilobed nucleus with large blue granules release pharmacologically active substances during allergic response (histamine, bradykinin, serotonin)

• Mast cell: myeloid small nucleus, packed cytoplasm of large blue granules in tissues, mucosa and epithelia release of granules containing histamine during allergic response (↑vascular permeability)

Immunoglobins – 4 chain glycoprotein molecule (monomer) made up of 2 light and 2 heavy chains • Light chains are Kappa (chr. 2) OR Lambda (chr. 22), heavy

chains dictate type of molecule (chr. 14) • Fab – fraction antigen binding variable region for Ag binding • Fc – constant region that carries out the effector functions • Chains held together by disulfide bridge – Hinge region allows

for flexibility/mobilitiy • Only IgM & IgD act as BCRs

• Idiotype = hypervariable 3D shape that will accommodate binding of a certain Ag o Each domain is made up of similar first 110 amino acids

corresponding to the variable domain o Variability based on genetic recombination

• Isotype = Class determined by the heavy chain – M, D, G, A, E • TCR is composed of 2 glycoprotein chains – alpha and beta

(have variable and constant regions) • Variable Regions: Light Chain = VJ; Heavy Chain = VDJ

o DNA rearrangements take place at the correct locations relative to the V, D, or J gene segments (within bone marrow)

o Rearrangements are guided by conserved non-coding sequences found adjacent to points at which recombination takes place – Recombination Signal Sequence (RSS) tell recombinant enzymes (RAG1 and RAG2) where to ‘nick’ genes

o TdT enzyme puts nucleotides btwn V and J and D and J at the recombinant sites generating greater diversity

o VDJ recombinase – act to carry out recombination (RAG1 and RAG2) w/o these enzymes ↓ capacity to handle pathogens due to no rearrangements

o Somatic Hypermutation = introduces point mutations into the V region of rearranged chains in the lymph node – ONLY in B-cells

• Omenn syndrome – autosomal recessive disease caused by mis-sense mutation in RAG genes resulting in lack of B cells and marked decrease in T cells failure to thrive, generalized rash, diarrhea and severe immune deficiency

• Severe Combined Immunodeficiency – autosomal recessive disease resulting from a null mutation in rag1 and rag2 genes no enzyme activity = total lack of B and T cells with defects in humoral and cell-mediated immunity

• Isotype Switching: only occur after B cells have been stimulated by an antigen - the same V region can recombine w/ other Constant portion genes to form new isotypes – Splice & Replace exons o Primary response = IgM

o Subsequence/Secondary response = IgG (made from same B cell)

Ig Structure – Glycoprotein molecules that are produced by plasma cells in response to an immunogen and function as antibodies (constitute ~20% of proteins in blood plasma) – antibodies with gamma globulins

• Antibody – antigen binding and effector functions (Fc) fixation of complemement and bind other cell types • If antibody molecule is treated with proteolytic enzyme (Papain)

results in broken peptide bonds (at hinge region) 2 Fab portions, 1 Fc portion

• IgG: Monomer, G1-G4, Most abundant serum Ig (Serum & Extravascular spaces) o Placental transfer – most abundant Ig in newborns o 2° response (isotype switching from IgM) o Activates complement o Opsonization = phagocytosis o ADCC from NK cells

• IgM: Pentamer held together by a J chain link, 10 binding sites o 1st Ig made by Fetus o 1° response o Fixes Complement

• IgA: Monomer in serum, Dimer in secretions (mucosa of GIT and Respiratory, saliva, tears, breast milk) o J chain & Secretory component broken off portion of

receptor o Prevents attachment by microorganisms to mucous

membranes (neutralization) • IgD: Monomer, acts as a surface receptor on B-cells • IgE: Monomer - least common serum Ig

o Allergic reactions (binds Fc receptors on eosinophils) & Parasitic infections (helminths) release of mediators to cause increased vascular permeability, broncho-constriction, and hypermotility of intestines

o Bind basophils and mast cells MHC (Major Histocompatibility Complex) • aka HLA = Human Leukocyte Antigen – highly polymorphic

• Located on short arm of Chromosome 6 • Class I = A, B, C; Class II = DP, DQ, DR • Haplotype = total set of alleles present on a single chromosome,

each individual has 2 Haplotypes • Co-Dominant inheritance, one from each parent • Class I is expressed on all Nucleated cells & interacts w CD8 T-

cells • Class II is expressed on APCs & interacts w CD4 T-cells

Genus Enterobacteriace: GRAM (-) found primarily in the colon (NF) -­‐ E. coli (Lactose Fermenter), Shigella, Salmonella, Proteus, Klebsiella (LF), Yersinia -­‐ Facultative anaerobes, Ferments glucose, oxidase (-), reduce nitrates nitrites,

contain endotoxin (LPS), some secrete exotoxins Antigens: -­‐ O antigen: located in cell wall (outer portion of LPS) – basis of serologic typing

o Lipid A – toxic component of LPS -­‐ H antigen: located on flagellar protein (only motile organisms – Proteus, Shigella -­‐ K antigen: capsular polysaccharide antigen (ID by Quellung reaction)

o Vi antigen in Salmonella Diagnosis: -­‐ MacConkey and EMB media: enterobacteriace differentiate btwn organisms in a

family (pink = lactose fermenters – Salmonella, E. coli)

-­‐ Urea media: used as screening tests (H. pylori produces urease) clolor changes from

orange-yellow to red-purple -­‐ TSI: triple-sugar test (lactose fermentation) – if lactose is fermented = yellow, if

glucose is fermented = yellow butt, red slope -­‐ Motility: Proteus swarming motility -­‐ Serologic tests: genus and serologic group determined by agglutination test (use

Antibodies) -­‐ Coliforms: E. coli frequently found in fecal-contaminated water (>4cfu/dl is

unacceptable) treat with chlorination Antibiotic Therapy: -­‐ Penicillins, Cephalosporons, AG, Sulphonamides -­‐ Frequent conjugation btwn strains and species spread of resistance via R-plasmids

Escherichia coli Facultative Anaerobe of colon (part of normal flora) reduces Nitrates to Nitrites Ferments Lactose pink colonies on MacConkeys, Oxidase (-)

***Most common cause of UTI Diseases: Gram (-) sepsis, neonatal meningitis, traveler’s diarrhea (some bloody), UTI Pathogenesis: adheres via Pili, possesses all 3 antigens, >1,000 serotypes -­‐ *Pili: allows for adherence to cells of jejenum and ileum (GIT or UT infections -

pyelonephritis) -­‐ Exotoxins: **enterotoxins that work at the gut

o High-molecular weight – Heat-labile (LT) Stimulates AC by ADP-ribosylation of Gs ↑cAMP = loss of fluid (watery

diarrhea) o Low-molecular weight – Heat-stabile (ST)

Stimulate GC by ADP-ribosylation ↑cGMP = Inhibition of Na+ resorption = loss of fluid and diarrhea

-­‐ Endotoxin: septic shock -­‐ Capsule: neonatal meningitis (prevents phagocytosis)

Diseases: Enterotoxins LT and ST • Enterotoxigenic E. coli (ETEC)** – bind jejunum and ileum (pili) and make 2 toxins

watery diarrhea, nausea, cramps, low grade fever (loss of fluid and electrolytes) “Traveller’s Diarrhea”

• Enteropathogenic (EPEC) – 2nd MC infantile diarrhea in undeveloped countries o Disrupts actin filaments of microvilli on brush border – resulting in malabsorption

of fat and diarrhea • Enteroinvasive (EIEC)** - acts at LI – Invades and destroys lining of mucosa

bloody and inflammatory diarrhea/desentry (neutrophils), cramping • Enterohemorrhagic (EHEC)** [aka Verotoxic E. coli – VTEC] o Produces Verotoxin = Shiga-like toxins that nicks 60S ribosomal subunit

(interferes with protein synthesis) causing watery bloody diarrhea but not inflammation/no neutrophils

o **Undercooked Hamburgers** o O157:H7 – HUS (hemolytic uremic syndrome), toxin interferes with protein

synthesis and lysis of RBC’s (↑BUN/creatinine due to acute renal failure); risk increased by treatment w/ antibiotics (jaundice, thrombocytopenia) - inability to ferment Sorbitol

• Enteroaggregative, Diffuse aggregative • UTI – strains with pili cause the infection (P-pili strains = pyelonephritis) o Motility of E. coli ascends to urethra into bladder and ureter into kidney – flank

pain, low grade fever, chills Pyelonephritis (WBC casts) o Cystitis, urethritis (UTI limited to bladder)– more frequent urination, burning, no

fever, pain • Septicemia – LPS Lipid A component is responsible (activation of macrophages - ↑TNF

and cytokines), fever, hypotension, DIC

• MCC of Hospital-acquired Sepsis** - after urinary, biliary or peritoneal infections (indwelling catheter)

• Neonatal meningitis – during birth (irritability, failure to feed, neck rigidity) do CSF analysis

Diagnosis: -­‐ MacConkey’s agar, EMB, motile -­‐ Isolate if large outbreaks

Treatment: -­‐ UTI: sulfa-drugs (inhibit folic acid synthesis) – Trimethoprim-sulphamethoxazole -­‐ Sepsis: 3rd generation Cephalosporons (possibly w/ AG) -­‐ Neonatal meningitis: Ampicillin + Cefotaxine -­‐ Diarrhea: rehydration, maybe sulfa-drugs, loperamide

Prevention: prophylaxis, urinary catheters, cranberry juice (low pH of urine) Salmonella Motile, Gram (-) rods, produce H2S, do NOT ferment Lactose colorless colonies on MacConkeys, Hektoen agar Ewing classification: S. typhi, S. choleraesuis, S. enteritidis (multiple serotypes) Kaufman and White: species named based on city in which first isolated (Genus, species, sub-species) -­‐ S. enterica subspecies typhi, paratyphi, choleraesius, enteritidis, typhimurium -­‐ Typhoid fever: S. typhi -­‐ Enteric fever: S. paratyphi -­‐ Enterocolitis: MCC is S. typhimurium

Characteristics: -­‐ O antigen -­‐ Flagellar antigen -­‐ Vi (virulence/capsular antigen) -­‐ S. typhi transmitted only by humans

Epidemiology: Poultry, eggs, Less Common Pets (turtles, snakes, lizards, etc), transmission by Humans Pathogenesis: Gastric acid is protective -­‐ Invasion of epithelial and subepithelial tissue of the intestines inflammation and

bloody diarrhea -­‐ Need >100,000 organisms to be infective -­‐ PMNs confine infection to the gut -­‐ Bacteraemia is rare

Diseases: • Enterocolitis - S. typhimurium is the MCC nausea and vomiting, diarrhea is mild,

bloody or non-bloody & self-limited (Clinical vignette: child playing with turtle) • Typhoid Fever – S. typhi multiply & enter phagocytes of Peyer’s Patches in SI

o Spread to phagocytes of Liver, Gallbladder & Spleen, colonization of gallbladder Chronic Carrier State (organism is continually excreted in feces)

o Bacteraemia (fever) o Hepatosplenomegaly, Peyer’s patches show many prominent follicles proliferating o S. paratyphi slow onset of illness preceded by constipation and fever

bacteraemia* develops, high fever, tender abdomen, and large spleen (hepatosplenomegaly), ROSE SPOTS ON ABDOMEN (1st week blood cultures positive, 3rd week it begins to resolve and cultured in stool)

o Complications: intestinal hemorrhage or perforation due to ulcer

• Septeacemia – S. choleraesius is the MCC in patients w/ underlying Chronic disease (Sickle Cell Anemia MCC of Osteomyelitis) lead to metastatic infections

o Initial symptoms are fever w/ little or no enterocolitis metastatic infection to bone, lung, or meninges

Lab Diagnosis: RBC/WBC in stool, non-lactose fermenters (pale colonies) -­‐ D/D: Proteus urease (+) -­‐ Serotyping O, H, and Vi -­‐ Widal’s Test: detection of rise in serum antibody titres in serial diluted concentrations

clumping/agglutination if (+) Treatment: -­‐ Enterocolitis: usually self-limiting, fluid and electrolyte replacement -­‐ Antibiotics (Ciprofloxacin inhibit DNA gyrase) treat chronic carriers (cholecystectomy

may be necessary) Vaccines: 3 types for high-risk regions -­‐ Vi capsular polysaccharide -­‐ Attenuated S. typhi -­‐ Killed whole S. typhi

Shigella Non-motile Gram (-) rods, do NOT ferment lactose colourless colonies on MacConkeys, do NOT produce H2S Epidemiology: Finger, Flies, Food, Feces **Day-Care Nurseries**, infective dose is very low (highly virulent ~100 organisms for infection) Pathogenesis: Invade Mucosal cells of Ileum & Colon local inflammation and ulceration = bloody diarrhea -­‐ O antigen: polysaccharide antigen -­‐ Shiga toxin* - AB component

• Bacterial Dysentery = Shiga Toxin (damage 60S ribosomal unit) – invasive, bloody diarrhea (shallow ulcers) o Fever, abdominal cramping (1-4 days), blood and pus diarrhea o S. sonnei accounts for 75% of cases in US o S. dysenteriae – causes most serious disease

Lab Diagnosis: -­‐ Methylene Blue stain of feces will detect presence of Neutrophils (blood and pus in

stool) -­‐ Isolate and grow out on EMB agar or TSI

Treatment: -­‐ Fluid and electrolyte replacement -­‐ Fluoroquinolones are DOC -­‐ Sulfa drugs can be alternate -­‐ Plasmids may carry multiple resistance

Vibrio Comma-shaped Gram (-) rods, sensitive to stomach acid Does NOT ferment Lactose colourless colonies on MacConkeys, Oxidase (+) V. cholerae, V. parahaemolyticus, V. vulnificus -­‐ O1 strain cause epidemic disease/outbreaks

Pathogenesis: Fecal-Oral, patients on Antacids -­‐ Infective dose very high -­‐ Toxin-mediated diarrhea -­‐ Produce mucinase dissolve protective glycoprotein coating over intestinal cells

facilitating adhesion of V. cholerae to brush border

• Cholera – caused by Vibrio cholerae o AB Exotoxin on Phage (lysogenized)- A subunit ADP-ribosylates Gs efflux of

Cl & water o death from massive Dehydration o Rice-water stools – little fecal matter, mostly just fluid, specs of mucus and shed

epithelial cells o **Cardiac & renal failure – acidosis and hypocalcemia from loss of bicarbonate

and potassium • Diarrhea – caused by Vibrio parahemolyticus **Seafood**

o Halophilic marine organism grows in 8% NaCl (distinguish from Cholera) o “Summer Illness”

• Cellulitis & Septis – caused by Vibrio vulnificus, o Halophilic marine organism, brakesh water o Hemorrhagic Bullae in skin (cellulitis) – shellfish handlers o Fatal septicaemia in immunocompromised individuals o **Chronic Liver disease is a major predisposition

Lab Diagnosis: -­‐ Thiosulphate-Citrate-Bile Salts (TCBS) media = Alkaline media -­‐ Sporadic cases in US -­‐ Distinguish from Enterobacteriaceae as Oxidasae (+) -­‐ Antiserum to rise in antibodies to serotypes

Treatment: -­‐ IV replacement of water and electrolytes -­‐ Tetracycline (broad spectrum) to reduce symptoms

Campylobacter Comma-shaped Gram (-) rods, Microaerophilic (best in 5% Oxygen), Lactose fermenting, C. jejuni grows well at 42°C **Seagull appearance** (polar flagella) **MCC of diarrhea in US Epidemiology: Chicken*, unpasterurized milk, Transmission: fecal-oral, **Diarrhea in Puppies Pathogenesis: unclear, Gastroenteritis – possible enterotoxin or invasion • Enterocolitis – caused by C. jejuni, particularly in children

o Watery, foul-smelling diarrhea followed by bloody stools o Atrophy or blunting of villi – inflammation of mucosa/submucosa o Predisposes to Guillian-Barre syndrome (ascending paralysis) via cross-reaction

of Abs with neurons (autoimmune - molecular mimicry) • Systemic Infection – MC infection bacteraemia caused by C. intestinalis

o Fever, malaise Diagnosis: -­‐ Isolate organism from stool and incubate at 42C -­‐ Blood culture for bacteraemia

Treatment: -­‐ Macrolides, quinolones

Helicobacter pylori Curved Gram (-) rods, Urease (+), silver stain Transmission: NF to stomach - food/water, person-to-person within families Pathogenesis: -­‐ Produces Ammonia from urea to neutralize stomach acid assisting survival -­‐ Causing an inflammatory response IL-1 and other cytokines will damage the

protective mucous layer of mucosa

-­‐ Inhibition of negative signals for acid production = ↑HCl ulcer -­‐ Attaches to mucus-secreting cells of gastric mucosa

Diseases: • Gastritis Duodenal Ulcers – recurrent pain in upper abdomen, frequent bleeding into

GIT o Pain relieved by food

• Risk factor for Gastric CA & Lymphomas o Type A Gastritis – autoiantibodies to IF (Pernicious anemia) o Type B Gastritis – H. pylori

Lab Diagnosis: -­‐ Urease Breath Test

o Evolution of 14CO2 after administration of radiolabelled urea -­‐ Gastric mucosa biopsies -­‐ Presence of IgG antibodies

Treatment: -­‐ Amoxicillin and Metronidazole, bismuth salts

Klebsiella Non-motile, Lactose fermenter K. pneumoniae - prominent antiphagocytic Capsule giving colonies Mucoid appearance *Opportunistic pathogen causing nosocomial infections (URTI) Pathogenesis: • Nosocomial Pneumonia – COPD, DM, alcoholism **Alcoholic + Smoker**

o Currant Jelly sputum (thick, bloody) Abscess formation • UTI – IV catheters Diagnosis: -­‐ Produce colored colonies on MacConkey’s

Treatment: AG + Cephalosporins Proteus Urease (+), Swarming Motility, Produces phenylalanine deaminase Antigens: -­‐ OX antigen can be purified and used to diagnosis Rocky Mountain Spotted Fever

from Ricketsia Epidemiology: Present in colon, water and soil Pathogenesis: • Hospital & Community-acquired UTI – Proteus vulgaris & mirabilis - urease raises

pH, forms Stones (Stag-horn calculi/Struvite due to supersaturated state) from Magnesium Ammonium Hydrochloride* leading to an obstruction and stagnation of urine bloody urine o Signs and symptoms are not sufficiently distinctive ascending infection o P. mirabilis causes most infections o Providencia rettgeri becoming important cause of nosocomial infections

Lab Diagnosis: -­‐ Swarming behavior on blood agar addition of phenylalanine alcohol to medium used

to inhibit motility -­‐ P. mirabilis indole (-), others are (+) breaks down tryptophan

Treatment: -­‐ AG or sulfa-drugs -­‐ P. rettgeri has some issues with multiple resistance -­‐ Tx involves getting urine pH back to normal (low)

Pseudomonas

Gram (-) rods, Obligate Aerobes (generates ATP by aerobic respiration), grow in water*, does NOT ferment Lactose, Oxidase (+) -­‐ Tolerate to disinfection (resistant to detergents, soap solutions, antiseptics) -­‐ High risk groups: burns, CF, immunosuppressed patients (low neutrophil count) -­‐ MCC of gram (-) nosocomial pneumonia

Pathogenesis: prominent Slime layer -­‐ Acts like a protective capsule/coat and mediates adherence to mucous membranes of

respiratory tract preventing binding of antibody -­‐ Gets lodged in lung very thick -­‐ Pigments:

o Yellow-Green pigment = Pyoverdin (Detection of burn infections) o Blue-Green pigment = Pyocyanin colored pus in wound and can damage cilia

and mucosal cells of respiratory tract o Fruity aroma

-­‐ Type III secretion system: transfers exotoxin from bacterium directly into adjacent host cells avoiding neutralizing antibody

-­‐ Common source in hospital sink or respiratory equipment -­‐ Colonize moist regions of skin and URT -­‐ Indwelling catheters UTI -­‐ Endotoxin: LPS possibility of sepsis -­‐ *Exotoxin A causes tissue necrosis inhibits protein synthesis by ADP-ribosylation

of EF-2 (like Diphtheria toxin) -­‐ Elastase and Protease which assist invasion of bloodstream

Disease: • Nosocomial Pneumonia (patient w/ CF) – P. aeruginosa • Endocarditis in IV drug users • Ecthyma Gangrenosum – black necrotic lesion due to protease/elastase • UTI • Malignant Otitis Externa (DM) can spread and damage/erode mastoid • Hot tub Folliculitis • Keratitis – corneal infections in contact lens wearers (homemade solutions) • Osteochondritis **Gym Shoes** Diagnosis: -­‐ Colorless colonies on MacConkey’s – Oxidase (+) -­‐ Presence of pigments fruity aroma -­‐ Confirmation based on biochemical tests or phage typing

Treatment: -­‐ Ticaricillin or Piperacillin (antipseudomonal PCN) + AG -­‐ Bring neutrophil count >500/uL -­‐ Trimethoprim-sulphamethoxazole used for B. cepacia, S. maltophilia

Bacteroides & Prevotella Anaerobic, Gram (-) rods, NF of colon -­‐ ~60% of vagina in women

Pathogenesis: -­‐ Endogenous infections via break in mucosal surface -­‐ Abscesses* of abdomen or pelvis -­‐ Tissue necrosis and ischemia facilitate growth -­‐ Polysaccharide capsule important for virulence -­‐ LPS endotoxin septicemia

Diseases:

• Peritonitis – B. fragilis possesses Polysaccharide Capsule important to virulence – Below Diaphragm

• Abscesses – P. melaninogenica primarily found in Oral Cavity – Above Diaphragm can aspirate and lead to oropharyngeal or lung abscesses

Diagnosis: black colonies Treatment: Metronidazole is DOC (also clindamycin) Haemophilus influenzae Gram (-) Coccobacillus, polysaccharide capsule Pathogenesis: **Incomplete Vaccination history** = meningitis (if vaccinated = Strep pneumoniae) -­‐ Serotyping based on polysaccharide capsule -­‐ Type B has a polyribitol phosphate capsule causing severe/invasive diseases

(meningitis and sepsis) -­‐ Some are unencapsulated and may still be pathogenic (not protected by vaccine) -­‐ Entry via URT -­‐ Most infections occur in children 6 mos 6 yrs -­‐ Greatest risk between 6 mos – 1 yr (decline in maternal immunoglobulins) -­‐ Up until 2 y/o their immune system is still immature and can’t generate sufficient

antibody to capsular polysaccharide (conjugated vaccine helps) Diseases: E-MOPS • Epiglottitis – NO OTHER AGENT CAUSES THIS! – Stridor - Can obstruct airway & become

life-threatening (DO NOT do airway examination) • Otitis Media and sinusitis (2nd MCC behind S. pneumoniae) – pain in infected site,

opacification of infected sinuses and redness with bulging of tympanic membrane • Meningitis in young children – 95% caused by Type B, β-Lactamase • Pneumonia – patient w/ COPD or chronic diseases with non-encapsulated strains

(consolidation, productive cough) Lab Diagnosis: growth on Chocolate Agar requires addition of Factor X & V (heme and NAD compounds), Quellung reaction Treatment: Ceftriaxone is DOC, Amoxicillin-clavulanate for URTI and otitis/sinusitis Prevention: Vaccine w/ Type B capsular polysaccharide conjugated to Diphtheria Toxoid (production of a stronger response so more antibodies to capsule) Bordetella pertussis Coccobacillary, Encapsulated, Gram (-) rods Epidemiology: *HIGHLY CONTAGIOUS, transmitted within airborne droplets – high school student w/ repetitive hacking, dry cough Pathogenesis: -­‐ Attachment mediated by Filamentous Hemagglutinin on pili Acute

Tracheobronchitis • Pertussis Toxin – B subunit binds to respiratory tract epithelial cells, A subunit ADP-

ribosylates Gi & permanently inactivates it, inhibits signal transduction failure of Lymphocytes to enter Lymphoid tissue (relative lymphocytosis) = Whooping Cough

• Synthesizes and exports Adenylate cyclase - inhibits Bactericidial activity of phagocytic cells

• Tracheal Cytotoxin – induce NO killing ciliated epithelial cells Diseases: -­‐ Acute Tracheobronchitis – Whooping Cough:

o Incubation – 6-7 days o Catarrhal – runny nose, common cold symptoms “whoop” cough after series of

hacking coughs accompanied by mucus (isolate organism)

o Paroxysmal o Convalascence – *COMPLICATIONS (pneumonia, CNS anoxia and exhaustion)

Lab Diagnosis: isolated on Bordet-Gengout agar during early Paroxysmal Stage (Catarrhal Paroxysmal Convalescent) -­‐ Lymphocytosis although caused by bacteria -­‐ PCR

Treatment: Erythromycin Prevention: new Acellular vaccine (antibody to filamentous haemagglutinin and toxoid) - DPaT vaccine Legionella Gram (-) rods staining faintly **no organism was visualized** requires Cysteine and Iron for growth (CYE agar) Epidemiology: water sources, Airborne transmission **Air-Conditioner w/ common water source** Pathogenesis: inflammation in interstitium, can spill out into blood stream -­‐ High risk: smoker + alcoholic -­‐ Mediate a cell-mediated immunity -­‐ Renal transplants are high risk (immunosuppressed)

Diseases: dry, hacking cough – non-productive • Atypical Pneumonia – L. pneumophila causes 90% of cases – inflammation in

interstitium o Varies mild influenza – prominent cough, non-productive, Pontiac fever o Mental confusion, Hyponatremia*, non-bloody diarrhea, proteinuria, hematuria

Treatment: Azithromycin or Erythromycin Lab Diagnosis: Gram stain will reveal Neutrophils but no bacteria, grown on Charcoal-Yeast extract agar Brucella Gram (-) rods, causes Brucellosis Epidemiology: ingestion of **contaminated Milk products** or occupational hazard, goat’s cheese Pathogenesis: Undulating Fever, long incubation period • Localize in Reticuloendothelial system Phagocytosed by macrophage some live

Intracellularly Granuloma • Enlarged Spleen and lymph nodes • Osteomyelitis Lab Diagnosis: fastidious on primary isolation -­‐ Requires enriched media -­‐ Tube agglutination test: titres >160 is diagnostic

Treatment: -­‐ Tetracycline + Rifampin

Francisella tularensis Gram (-) rod, causes Tularemia, Enzootic in every US state **Arkansas, Missouri, Mississippi, Texas** Epidemiology: Dermacentor tick (heat sensors) acts as a vector between Rabbits, Deer & Rodents (offspring ticks can be born with the infection - transovarially) Pathogenesis: Ulcer @ site of entry Ulceroglandular* • Localize in Reticuloendothelial system live Intracellularly formation of

Granulomas (abscesses can form) • Fever, lymphadenopathy Treatment: Streptomycin (attenuated vaccine for high-risk groups)

Yersinia pestis Small, Gram (-) rods, Bipolar staining (safety pin) Epidemiology: Highly virulent (1-10 bacteria), SE Asia, Sylvatic & Urban cycles (rats & fleas), Quarantine Pathogenesis: Bubonic or Pneumonic plague • Coagulase – clotting of blood in flea’s stomach leads to starvation bite Humans and

regurgitate bacteria • F-1 Envelope Capsular Antigen – virulence factor • *V & W Antigens – allow bacterium to survive Intracellularly Extremely tender

LNs – Lymphadenopathy bubous • *YOPs – Yersinia Outer Proteins – act as a Protease & prevents synthesis of TNF,

Type III secretion systems, inhibit Phagocytosis & Cytokine production, inhibition of host defenses (Salmonella)

• Exotoxin – DIC, Cutaneous Hemorrhages, septic shock Diseases: -­‐ Bubonic Plague: swelling and painful LN, fever, myalgia and prostration

o Possible septic shock and pneumonia -­‐ Pneumonic Plague: inhalation or from circulation of septic emboli from bubonic

plague o Mortality 100%

Lab Diagnosis: must prevent Aerosol ( Pneumonic Plague), Safety Pin appearance -­‐ Serologic is method of choice

Treatment: Streptomycin + Tetracycline (isolation for 72 hours after treatment) -­‐ Notifiable disease -­‐ Prophylaxis administered to close contacts

Pasteurella multocida Encapsulated, Gram (-) rods Epidemiology: Cat & Dog bites mixed infections Pathogenesis: -­‐ Capsule:

Diseases: • Rapidly spreading Cellulitis – ulcerated lesion • Complications – Osteomyelitis Treatment: Penicillin G Immunology MHC (Major Histocompatibility Complex) • aka HLA = Human Leukocyte Antigen – highly polymorphic • Located on short arm of Chromosome 6 • Class I = A, B, C; Class II = DP, DQ, DR • Haplotype = total set of alleles present on a single chromosome, each individual has 2

Haplotypes • Co-Dominant inheritance, one from each parent • Class I is expressed on all Nucleated cells & interacts w CD8 T-cells • Class II is expressed on APCs & interacts w CD4 T-cells MHC (Major Histocompatibility Complex) • aka HLA = Human Leukocyte Antigen – highly polymorphic and expressed on various

cell types o Success of a transplant depends on the donor’s and recipient’s HLA genes o Alloantigens – differ among members of the same species (foreign and recipient

can produce antibodies to that organ/blood)

• Located on short arm of Chromosome 6 o Class I = A, B, C expressed on all nucleated cells

HLA-A, B, C = 2 alleles (maternal and paternal) 6 total Long alpha chain with 3 domains and supported by the short beta chain

(beta2-microglobulin) – anchored by membranous portion – cytosolic portion for signal transduction

Alpha1 and alpha2 form a groove for antigens (foreign, bacterial viral peptides) – alpha helix and beta-pleated sheets

Alpha3 is the site to which CD8 binds (recognition of antigen or self cell)

Can bind only 8-10 amino acid peptide from a pathogen Peptides from cytosol

o Class II = DP, DQ, DR expressed primarily on APC (B-cells, monocytes, macrophages, Langerhan’s cells, dendritic cells* [nucleated also])

DR has 2 beta chains = 2 proteins (4 expressed on cell – 2 from each allele)

DP and DQ only 1 protein from each parent 8 total 2 alpha and 2 beta of equal length alpha1 and beta1 form binding

groove Alpha2 and beta2 are recognized by CD4 Can bind a larger peptide (10-15 amino acids) Peptides from vesicles

o Class III = TNF, LkT, complement proteins • TCR, CD3 (signal transduction), CD4/8 • Different individuals can process the same antigen using different epitopes of that

antigen • Haplotype = total set of alleles present on a single chromosome, each individual has 2

Haplotypes (maternal and paternal) o Gene linkage (increased likelihood that genes are passed together – not

segregated) o Multiple alleles = polymorphic SURVIVAL (evolution to survive mutated

antigens) • Co-Dominant inheritance – 2 HLA proteins expressed on each cell (one from each

parent) Selection of Lymphocytes Bone Marrow = 1° lymphoid organ development of B-cells • Bone marrow stroma + Interdigitating cells kill auto-reactive B-cells via Apoptosis =

Clonal Deletion (production of an idiotype that binds normal body constituents) • Clonal Anergy kills the auto-reactive B-cells that make it out of the bone marrow to

periphery – within 2° lymphoid organs • Pro-B cell (undifferentiated – heavy chain rearrangement) Pre-B cell (heavy chain +

surrogate light chain) Thymus = 1° lymphoid organ development of T-cells • Thymus – bilobed structure with an outer cortex (immature T-cells, APC, CEC) and

inner medulla made up of epithelial, dendritic cells, macrophages that nourish the developing thymocytes

• T-cells begin to express their TCR to react with antigens, not self molecules o T-cells must recognize self-MHC (class I or II) on APCs = Positive Selection o T-cells must recognize foreign Ags associated w/ self-MHC in periphery

o T-cells must NOT recognize self peptides associated w/ self-MHC within medulla = Negative Selection (look at it, but don’t react – if T-cell reacts kill off) – keep if they only produce a weak response

• Leave Thymus differentiate into CD4 or CD8 and express TCR and CD3 (signal transduction)

Secondary Lymphoid Organs – mucosal associated – MALT and GALT, LN, spleen Lymph Nodes -­‐ B-cells enter LN thru afferent lymphatics follicles rich in B-cells in the cortex -­‐ T-cells enter LN thru afferent lymphatics aggregate in paracortical zone -­‐ Antibodies are released thru medulla and efferent lymphatic duct to thoracic duct

and finally the bloodstream and general circulation Spleen -­‐ Initiates immune response to blood-borne antigen -­‐ Splenic artery enters the capsule and branches into arterioles surrounded by “cuffs” of

lymphocytes PALS (periarteriole lymphoid sheath) and b-cells form follicles Recirculation through specialized blood vessels – High Endothelial Venules -­‐ Migration involves interaction btwn adhesion molecules -­‐ Maximizes possibility of B and T cells to encounter an antigen

Processing & Presentation of Ag Exogenous/Endosomal Pathway • Dendritic cells & macrophages load partially degraded peptides (of invading Bacteria)

onto MHC class 2 molecules & present it to the naïve T-cell (CD4 to help B-cell make Ab to that bacteria)

• When the MHC class 2 molecule is produced in the ER of an APC, α, β, & Invariant chains are synthesized – Invariant blocks the binding groove from loading normal cellular components/self peptides

• During transportation through Golgi, the vesicle (phagolysosome with engulfed foreign protein) fuses with an Endocytic Vesicle Invariant chain gets degraded Load partially degraded Ag particles into the peptide binding groove of MHC class 2 molecule o Presentation of peptide-MHC complex to CD4 helper T-cells on APC cell surface

(APC enter LLN via afferent lymphatics and trapped in LN ↑chance of interaction with naïve T-cell)

o Binding of TCR of naïve T-cell to MHC class 2 peptide on APC provides 1st signal for T-cell activation

• Co-stimulatory molecules (CD28B7 & LFA-1ICAM-1) provides 2nd signal for T-cell activation o CD28 on CD4 T-cell binds B7 (CD80/86) on APC o Integrins – LFA-1 on CD4 T-cell binds ICAM-1 on APC o Production of cytokines to activate each other

APC IL-1, TNF-alpha, IL-12 Th1-cell TNF-beta, IFN-gamma, IL-2,4,5

• TH0 Th1 if Ag is intracellular and evoke a strong innate response (partner with CD8 T-cell) production of IL-12 by macrophage or IFN-γ by NK cells (promote development of Th1, inhibit proliferation of Th2) – CELL-MEDIATED IMMUNITY

• TH0 Th2 if Ag is exogenous and a weak innate response (partner with B-cell), production of IL-4/5 & IL-10 amplify differention/proliferation (inhibitory signals to Th1) Plasma cell Ab secretion = HUMORAL IMMUNITY

Endogenous Pathway

• After invasion by Virus/Intracellular Bacteria, some foreign Proteins synthesized in the cytosol using host machinery are degraded within Proteasomes (ubiquitin-protease system – “shreds” the foreign/viral proteins to make smaller in order to be placed in peptide binding groove for presentation)

• Peptides are sent through a TAP Complex into the ER & get loaded onto MHC class 1 molecules

• These MHC class 1 molecules are then transported to the cell membrane and available to be presented to CD8 cytotoxic T-cells

Superantigens • Viral or Bacterial proteins that crosslink TCR (beta chain) & MHC class 2 molecule

(beta chain) in absence of Ag specific recognition – bind OUTSIDE of the Ag-binding cleft activate a large number of T-cells via large amounts of cytokines being produced

• T-cells generate overproduction of IFN-γ activates macrophage to produce TNF-α, IL-1 and IL-6 induce systemic toxicity

Bare Lymphocyte Syndrome (autosomal recessive) • MHC class 2 deficiency CD4+ deficiency (therefore deficiency of Th2 and Th1) due

to failure of Positive selection • Suffer from moderate to severe Hypogammaglobulinemia Generation of Humoral Effector Mechanisms -­‐ Infectious disease multiply in extracellular spaces need for protection of them -­‐ Humoral response = antibody B cell, with help from Th2, APC, and cytokines -­‐ Secondary lymphoid tissue provide unique microenvironments through which all

components come to together to generate and an efficient Ab response (LN, Spleen, MALT)

Antibody Contribution • Neutralize the ability of pathogens to bind to target cells (can’t internalize) & prevent

bacterial toxins from entering cells • Facilitate uptake of pathogens via Opsonization • Activate Complement proteins to augment clearance B-cells Antibody Production [B-cells can also act as APC] -­‐ T-cell independent -­‐ T-cell dependent (Th cells) -­‐ Mature in BM encounter antigen in LN = activated and transforms into plasma cells

to secrete immunoglobulins CD19, 20, 21 are B-cell markers – **CD21 is a receptor for EBV** Thymus-Dependent Antigens • Requires direct contact of B-cells with Th cells & their cytokines – Antigen

internalized and processed and loaded on Class II MHC to present to naïve T-cell = Exogenous Pathway

• Armed helper T-cell (already seen the antigen being presented from another APC) activate B-cells (acting like an APC) to proliferate and differentiate when they recognize the appropriate MHC Class II complex = Linked Recognition

• Co-Stimulatory interactions: CD28 binds B7 production of IL-2, CD40L binds CD40 release of Cytokines (IL-2) from CD4 differentiation into Ab-secreting or memory cells (formation of prominent germinal centers) o *CD40L-CD40 interaction required for class switching from IgM to IgG (IL-4,

IL-5) Thymus-Independent Antigens

• Antigens that possess no peptide structure cannot be recognized by T-cells – LPS of Gram (-) bacteria

• Directly stimulate B-cells to cause proliferation & secretion of Antibodies • Response is generally weaker only IgM secretion – NO immunologic memory Isotype Switching • Induced in response to Cytokines secreted by TH2 cells • Once you splice out an isotype, you can’t go back and ever make that isotype again Affinity Maturation = clonal selection results in predominance of clones capable of making Abs with increasing affinity to the Ag due to Somatic Hypermutation X-linked Hyper-IgM Syndrome: deficiency of IgG, IgA, and IgE and elevated levels of IgM -­‐ Defect in gene encoding for CD40 ligand on Th cell -­‐ Therefore Th-cells fail to give co-stimulation necessary for the B-cell response -­‐ T-independent antigens are unaffected -­‐ Recurrent respiratory infections (Pneumocystis jiroveci)

Generation of Cell-Mediated Effector Mechanisms Identify & eradicate Antigens that arise from inside the cells of the body = Viruses, Parasites, Intracellular bacteria (Listeria, M. tubo/leprae, Brucella) Activation of naïve T-cells proliferation & differentiation into Armed Effector cells T-cell Development: TCR-, CD4-, CD8- TCR+, CD4+, CD8+ choose to keep one of the CDs when Mature -­‐ TCR+, CD4+, CD8- = T-helper cell -­‐ TCR+, CD4-, CD8+ = cytotoxic T-cell

• Diversification – receptor rearrangements develops variable TCR • MHC Restriction – interaction with self-MHC molecules in the cortex = Positive

Selection • Self-non-self Discrimination – reaction with self-Ag in the medulla (weak = keep,

strong = throw-away) = Negative Selection • Functional Capacity – competent CD4 or CD8 cells leave the thymus T-cell Activation • T-cells in circulation are in a Resting State • During immune response, T-cell enlarges cytoplasmic & nuclear volume (Blast

Transformation) Ready to mount a cell-mediated immunity reaction • Effector cells can have direct cytotoxicity (virally infected cells) • Th1-cell partner with CD8+ cells to remove IC bacteria (Delayed Hypersensitivity

Reaction) GRANULOMAS (TB, Leprosy) **TCR associates with accessory molecular complex CD3 to transmit signals when engage by Ag -­‐ TCR: alpha/beta or gamm/delta (heterodimer) -­‐ CD3: epsilon/delta, zeta/zeta, gamma/epsilon chains signal transduction

Direct Cytotoxic Response • Resting Cytotoxic T-Lymphocyte (CTL-Ps) are incapable of killing • Cytotoxicity involving CD8 cells and help from NK cells and macrophages • 1st signal = TCR & CD8 interacts with Ag-MHC complex on APCs (class I) • 2nd signal = IL-2 produced by activated CD4+ helper cell (presented via Class II –

exogenous pathway from necrotic cells lysed by viral infections in periphery) o IL-2 receptors are up-regulated on CTL o Binding of IL-2 = proliferate & differentiate into Cytotoxic cells capable of

killing • Cytotoxic T-cell Killing:

o FasL expressed on Cytotoxic T-cell to interact with Fas-receptor on infected target cell Death Domains open activating kinases (phosphorylation of down-stream targets) to phosphorylate CASPASES = APOPTOSIS

o Kill target via delivery of TOXIC GRANULE CONTENT that induces Apoptosis (Granzyme, Perforin)

NK Cell Activity • Increased in the presence of IFN-α, IFN-β & IL-12 produced by macrophages ADCC killing = Antibody-Dependent Cell-Mediated Cytotoxicity • Preformed antibodies (vaccines) prevent viruses from becoming internalized and

eliciting an infection (Th2 cells B-cells to produce antibodies) • NK cells can bind to the free Fc portion of IgG when interacting with a target cell

Lysis via lytic enzymes, TNF, and perforins Intracellular Infections (Mycobacterium TB in lung parenchyma) – Th1 subset plays important role in defense against IC organisms want to avoid CD8 killing so you don’t destroy lung tissue • TH1 cell secretes IFN-γ activates Macrophages to kill Bacteria (and make more IL-

12 which will activate more CD4 cells to differentiate into Th1 cells) can form GRANULOMAS