Introduction Klebs--1883 discovered Loefflers--1884 cultured Also known as KLB Emil von Behring-...
-
Upload
mae-barnett -
Category
Documents
-
view
229 -
download
0
Transcript of Introduction Klebs--1883 discovered Loefflers--1884 cultured Also known as KLB Emil von Behring-...
Introduction
• Klebs--1883 discovered• Loefflers--1884 cultured• Also known as KLB • Emil von Behring- 1890
produced antitoxin• Awarded nobel prize
Emil Von Behring
Morphology
• Gram positive bacilli. 3-6 μ x 0.5-0.8 μ.• v or k or L shape.• Chinese letter pattern, angular arrangement• Metachromatic granules. volutin granules,
polymetaphosphate energy storage depots• Alberts stain – green and bluish black• Nonmotile noncapsulated, nonsporing• pleomorphic
Cultivation
• Loefflers serum slope– creamy white colonies in 6-8 hrs
• Potassium tellurite medium—black colonies
• Blood agar
Biochemical reactions
• Hiss serum
• Ferments glucose ,maltose with acid only
• Lactose, sucrose, mannitol not fermented
• Urease negative
• Starch –only gravis type, not intermedius or mitis
Pathogenicity
• Produces exotoxin
• Lysogenic conversion with beta phage
• Toxin – heat labile protein
• A and B fraction
• Toxicity- disease
• Antigenicity- immunity
• Toxoid – toxin without toxicity
Toxin
Mechanism of action
-B subunit binds to receptor-toxin molecule cleaved at protease sensitive site between A-B portion (remain bonded by disulfide link)-receptor-toxin complex englufed into vesicle of host cell-reduction of disulfide bond, A subunit released into cytoplasm-Necrosis/neuotoxic effects on organism by exotoxin
Biotypes
1)gravis(13 types)-most serious diseaseColonies: large, irregular, gray
2)mitis(40 types)-mild illnesscolonies: small, round, convex, black
3)intermedius(4 types)-intermediate severityColonies: small, flat and gray
Diphtheria
• Children, fatal if not treated in time• Exclusively human disease• Droplet infection- fomites• Fever, cervical lymphadenopathy,
pseudomembrane• Myocarditis arrhythmia fatal• Polyneuropathy, paltine paralysis• Rare in adults.
Pseudomembrane formation
Thick membrane lining throat that interferes with eating, drinking and breathingContents: WBC, RBC, bacteria, disintegrating epithelial cellsCause: fibrinous exudate from local necrosis by exotoxin (removal of PF may cause bleeding)Localization: faucial, laryngeal, nasal, otitic, conjunctival, genital, cutaneous
Faucial:
Signs: sore throat, fevercomplications: prostration, dyspnea, asphyxia, arhythmia,
difficulties of speech, vision, swallowing, movement
Septic: Ulceretic:
Clinical classification
i) Malignant (hypertoxic) diphtheria Signs: severe toxemia and adenitis, lymph glands swelling in the neck
Complications: death-circulatory failure, paralytic sequelaeii) Septic diphtheria:
Signs: ulceration with pseudomembrane formation and cellulites (gangrene around pm)
iii) Hemorrhagic diphtheriaSigns: local and general bleeding from edge of psudomembrane, conjunctival, epistaxis and purpura
Complications
1)Asphyxia-obstruction of resp tract2)Acute circulatory failure3)kidney failure 4)paralysis-soft palate, eye muscles, extremities (3rd-4th week)5)septic sequelae-pnemonia, otitis media
Laboratory diagnosis
• Sample collection: Throat swab or swab from membrane
• Microscopy: Gram stain and Alberts stain
• Culture: Loefflers and PT
• Biochemicals
• Virulence test in vivo and in vitro
Virulence test contd
In vivoGuinea pig– subcutaneous
intradermal
Test and control animals to be used
In vitro
Eleks gel precipitation test
Toxigenicity test (virulence test)
i) Animal inocculation-bacteria culture emulsified in water and 0.8 ml injected into 2 guinea pigsGP A-has dipht antitoxin (injected 2 hours before)GP B-Doesn't have antitoxin
Result: Guinea pig B dies.
ii) Elek's gel precipitation test-filter paper saturated with antitoxin is placed on agar plate with 20% horse serum-bacterial culture streaked at right angles to filter paper
iii) tissue culture test-incorporation of bacteria into agar overlay of eukaryotic cell culture monolayers.Result: toxin diffuses into cells and kills them
iv) PCR assays-test presence of specific bacteriophate gene (tox)
Elek's gel precipitation test
EPIDEMIOLOGYEPIDEMIOLOGY
• Formally important pediatric diseaseFormally important pediatric disease• Developed countries - EradicatedDeveloped countries - Eradicated• Developing countries serious problemDeveloping countries serious problem• Rare in 1Rare in 1stst year – maternal antibodies year – maternal antibodies• Peak 1-5 years, 5-10 years- decreases there afterPeak 1-5 years, 5-10 years- decreases there after• Immunity – sub clinical infectionsImmunity – sub clinical infections• Carriers outnumber cases – throat & nasalCarriers outnumber cases – throat & nasal• Rarely spread through milkRarely spread through milk
Prevention• Active immunity- DPT dosage
– Antitoxin level – 0.01/ ml protectiveAntitoxin level – 0.01/ ml protective
• Passive immunity- ADS– When susceptibles are exposedWhen susceptibles are exposed– 500 – 1000 units sc of Anti Diphtheritic Serum ( ADS)500 – 1000 units sc of Anti Diphtheritic Serum ( ADS)
• Combined immunisation– First dose of adsorbed toxoid on one armFirst dose of adsorbed toxoid on one arm– ADS on another armADS on another arm– To be continued with full course of active To be continued with full course of active
immunizationimmunization
Preventiona) DTP (DPT)- • Formal toxoid - Incubation of Toxin at pH 7.4 -7.6 for 3 – Formal toxoid - Incubation of Toxin at pH 7.4 -7.6 for 3 –
4 weeks at 37 4 weeks at 37 °°C C • Adsorbed toxoid – purified toxoid adsorbed on to Adsorbed toxoid – purified toxoid adsorbed on to
aluminum phosphate or hydroxidealuminum phosphate or hydroxide
• triple vaccine given to children.
trivalent preparation
• Diphtheria toxoid, Tetanus toxoid and Pertussis vaccine
Td- contains absorbed tetanus and ten-fold smaller dose of diphtheria toxoid.
b) Schedule
i) primary immunization –
- infants and children - 3 doses, 4-6 weeks - 4th dose after a year - booster at school entry
ii) Booster immunization
- adults - Td toxoids used (traveling adults may need more)
Shick test-to test sensitivity (allergic reaction)
Treatment
• Antitoxin – 20,000 to 1 lakh unitsAntitoxin – 20,000 to 1 lakh units
• Antibiotic therapy – PenicillinAntibiotic therapy – Penicillin
• Carriers - ErythromycinCarriers - Erythromycin
Patch in the throat
• Diphtheria
• Streptococcal tonsillitis
• Oral thrush– Candida albicans
• Spirochete- Borrelia vincenti
Other Corynebacteria
1. C. ulcerans:
– Diphtheria like lesions
– Spread thru milk
– Antitoxin protective, erythromycin
2. C.minutissimum- – Erythrasma
3. C. tenuis:- Trichomycosis axillaris
4. C.pseudotuberculosis: – Veterinary importance
5. C.parvum:– Immunomodulator
6. A. haemolyticum:– pharyngitis, skin ulcers
7. C.jakieum:– Skin inf/ BSI in IC. Rx- Vancomycin.
Diphtheroids
• Morphologically resembling diphtheria but do not cause any disease.
• Present as commensals in throat, skin
• Do not contain metachromatic granules.
• Do not produce any toxin ie virulence test is negative.
• C.hofmani, C.xerosis, C.pseudodiphtheriticum