Microbiology of the Skin Flashcards
Staph aureus
Aerobic cocci
Impetigo, SSSS, abscess
Corynebacterium minutissimum
Coryneform bacteria
Erythrasma
Proprionobacterium acnes
Coryneform bacteria
Acne vulgaris
Malassezia furfur
Yeast
Pityriasis versicolor and folliculitis
Demodex mites
Parasite
Rosacea
Impetigo (cause, population, affected skin layer, 2 types, sxs, tx)
Due to staph aureus.
More common in children.
Disrupts epidermis.
Non-bullous type – Honey-colored crusting. Vesicles and pustules. Staph aureus > strep pyogenes.
Bullous type – due to staph aureus phage II toxin disrupting desmoglein 1 → blister. Acts as localized form of SSSS. Prodrome of malaise, fever, diarrhea. Flaccid bullae. Most common in neonates.
Tx – cover affected site to prevent spread, topical antibiotics (mupirocin), or oral antibiotics for high risk patients.
Ecthyma (cause, affected skin layer, sxs, tx)
Strep pyogenes or staph aureaus. Follows trauma. Infects dermis. Painful ulceration, crusting, and heals w/ scarring. Tx w/ oral abx.
Abscess (sxs, cause, affected population, risk factors, often mistaken for, tx)
Collection of pus w/ surrounding fibrous reaction. Tender red nodule that becomes fluctuant (full of pus)
Staph aureus most common cause.
Common in adolescents and young adults.
Risk factors include diabetes, old age, immunosuppression, obesity, uncleanliness
Often mistaken for ruptured epidermoid cyst.
Tx – warm compresses, incision / drainage, oral antibiotics
Furuncle
Abscess that involves hair follicles
Carbuncle
Collection of furuncles
Erysipelas (Cause, affected skin layer, sxs, affected population, tx)
Due to strep pyogenes. Infection of dermis → red plaque w/ sharp borders. Fever, chills, malaise. Commonly affects elderly px. Tx w/ oral antibiotic.
Erythrasma (Cause, affected skin layer, sxs, diagnostic tool, tx)
Overgrowth of normal flora cornyebacterium minutissimum infects epidermis.
Well-defined red patches w/ red scale. Affects moist areas (skin folds, intertrigo). Most often in groin, sometimes toes. Often asymptomatic.
Wood’s lamp exam shows coral red fluorescence
Tx includes topical antibiotics or antifungal agents (works via anti-inflammatory effect)
Tinea infections (cause, source, diagnostic tool, tx)
Dermatophytes (TEM): trichophyton, epidermophyton, and microsporum
Source: anthropophilic, zoophilic, geophilic (soil)
Zoophilic transmission may cause a kerion (massive inflammation of hair follicles)
Diagnosed via KOH. Long branching (septate) hyphae w/ transverse areas of pallor.
Tx w/ topical antifungals (focal) or oral antifungals (widespread or hair follicles)
Tinea capitis
Head
White scaling patches w/ hair loss.
Common in kids
Tinea corporis
Body
Red scaling plaques w/ annular configuration