6 bacterial infections of the skin
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Transcript of 6 bacterial infections of the skin
BACTERIAL INFECTIONS BACTERIAL INFECTIONS OF THE SKINOF THE SKIN
IntroductionIntroduction
Infections with pyogenic (pus forming) bacteria
usually Staphylococcus aureus and/or Streptococci (usually Group A β haemolytic Streptococci - GABS)
Factors in development of bacterial skin infection
1) the portal of entry 2) the host defences 3) the pathogenic properties of
the organism
Classification
- primary infections (pyodermas) - secondary infections
Primary infections (pyodermas)
infections that are produced by the invasion of normal skin by a single species of pathogenic bacteria
Secondary infections
Infections after the integrity of the skin has been broken, or the local immune milieu is altered by the primary skin condition
AD, scabies, tinea, …may show mixture of organisms
Staphylococcus - Commonly carried in nose(35%), perineum (20%), axillae and toe webs (5-10%) - Staphylococcus causes impetigo,
folliculitis, and carbuncles plus deeper infections. - Staph. toxins (epidermolytic) cause
bullous impetigo and SSSS( Staphylococcal
scalded skin syndrome).
Streptococcus - - Rarely found on normal skin, often in throat
(10%),occasionally in nose - Main pathogenic type – Lancefield Group
A. - Causes cellulitis, lymphangitis, regional lymphadenitis - Post streptococcal state (1-3 weeks later)
can produce – acute GN, rheumatic fever, rheumatism, erythema nodosum, psoriasis.
Normal FloraNormal Floraorganisms that characteristically
survive and multiply in various ecologic niches of the skin
S. epidermidis is the principal staphylococcal species
Candida Malasazia furfur ,
propionbacterium acne
Superficial Cutaneous Superficial Cutaneous infectionsinfectionsImpetigo
infections in the epidermisUntreated pyodermas can extend
to thedermis, resulting in ecthyma
Two clinical patterns
Bullous impetigo and Nonbullous impetigo
Non-Bullous Impetigo
70% of impetigo industrialized countries -- S. aureus
and less often by group A streptococcus in developing countries – group A streptococcus remains a common cause
Occurs in children of all ages and adultsusually spreads from nose to normal
skin
Cutaneous Lesionsinitially a transient vesicle or
pustule honey-colored crusted plaque
Sunounding erythem90% of prolonged,untreated –
regional LAPMay progress to Ecthyma
Bullous Impetigoby phage group II S. aureuThree types of eruptions 1) bullous impetigo, 2) exfoliative disease( SSSS) 3) staphylococcal Scarlet feverExtracellular exfoliative toxins
("exfoliatin") types A and B
Cutaneous lesions more common in newborns and
infantsrapid progression of vesicles to
flaccid bullaebullae arises on normal skinfluid clear yellow- dark yellow –
tubid- collapse – may crust
Laboratory
Gram stainCultureHistology
Treatment - good hygiene removal of crusts. - Antibiotics - topical if mild - mupirocin,
fusidic acid, - Systemic if severe, multiple
lesions, - cloxacillin,
erythromycin, amoxi+ clavulanic acid, cephalexin
Ecthyma usually a consequence of neglected
impetigocharacterized by thickly crusted
erosions or ulcerationsCaused by Group A Strept and/or
Staph
Commonest in children or debilitated adults, homeless and soldiers
most commonly on the lower extremities
ulcer has a “punched out” appearance
Covered with dirty greyish-yellow crust
heals slowly
Treat as impetigo
Folliculitis
a pyoderma that begins within the hair follicle
a small, fragile, dome-shaped pustule occurs at the infundibulum (ostium or opening) of a hair follicle
Children – scalpAdults - beard area, axillae,
extremities, and buttocksCan complicate to Furuncles if
untreated
Furuncles – boil deep-seated inflammatory
nodule that develops around a hair follicle
areas with friction, occlusion, and perspiration
usually from a preceding, more superficial folliculitis
Cutaneous Lesions
solitary or multiple hard, tender, red folliculocentric
noduleundergoes abscess formation
Ruptures
Carbunclemore extensive, deeper,
communicating, lesion that develops when multiple, closely set furuncles coalesce.
more serious inflammationred and indurated, and multiple
pustules soon appear on the surface, draining externally around multiple hair follicles scar
fever and malaise - ill
beware of bacteremia from such lesions esp when appears on the face
infection such as osteomyelitis, acute endocarditis, or brain abscess
recurrent furunculosis
Treatmenta systemic antibiotic as impetigo
for mild casessevere infections or infections in
a dangerous areas - maximal antibiotic dosage by the parenteral route
drain if abscess
Erysipelascaused by group A β-hemolytic
streptococcusacute infection of skin- level of part
of dermissuperficial cellulitis with marked
dermal lymphatic vessel involvementface or a lower extremitysuperficial erythema, edema with a
sharply defined margin to normal tissue
there may be portal of entryRecurrent erysipelas – tinea
pedis, lymphedema surgery Can cause lymphedema
Cellulitisinfection extends deeper into the
dermis and subcutaneous tissueS. aureus and GAS – common causeslooks erysipelas but lack of distinct
margins, deeper edema, surface bulla/necrosis
can go deep if untreated – fesciitis regional LAPportal of entry evident if half of cases
Treatment Supportive - rest, immobilization, elevation,
moist heat, analgesia.Dressings -cool sterile saline dressings for
removal of purulent exudates and necrotic tissue
Surgical - Drain abscess
Antimicrobial Therapy
- against strept in erysipelas - against staph in cellulitis + /-
against strept
THANKSTHANKS