Cutaneous Microbiology Flashcards
1
Q
Cutaneous flora
A
prevent infection by pathogenic organisms
- hydrolysis of skin lipids in sebum to free FA –> toxic to some bacteria
- aerobic Gram+ cocci, Gram- bacteria, corneyform bacteria, yeast, parasites
- overgrwoth lead to inflammatory diseases
- transmitted by carrier without symptoms
- cultures must be interpreted in light of normal flora
2
Q
Impetigo
A
Predominantly affects children
secondary impetiginization can affect any age group
- Non-bullous due to S. aureus and some times S. pyogenes
- compromise of skin barrier allows superficial infection
- yellow, honey-colored crust, vesicles, pustules, non-healing wound may suggest impetiginization
- Bullous due to S. aureus phage II type 71
- secreted toxins mediate disease by disrupting desmoglein
- occurs on intact and compromised skin
- flaccid bullae with prodrome of malaise, fever, diarrhea
- children appear non-toxic, rapid resolution
diagnosed via clinical presentation + culture of wound base or bulla fluid
treated by covering site (prevent transmission), topical abx for local, oral abx for generalized
3
Q
Ecthyma
A
typically related to trauma and occurs at any age
- due to S. pyogenes or S. aureus
- begins with pustules and vesicles, ulcerations develop with thick, adherent crust and heals with scarring
- diagnosed via wound culture
- oral abx
4
Q
Abscess, Furuncle, Carbuncle
A
Abscess: collection of pus with surrounding fibrous rxn
Furuncle: abscess that involves a hair follicle
Carbuncle: a collection of furuncles
- most common amound adolescents and YA
- risk factors are diabetes, immunosuppression, obesity, poor hygiene
-due to S. aureus, anaerobic bacteria in groin
- may occur at any site, favors sites of trauma or friction
- tender, red nodule that becomes fluctuant
- absence of systemic symptoms
- diagnosed via clinical & culture of purulent exudate
- treated by warm compresses, incision and drainage, oral abx if perinasal, large/recurrent, surrounding cellulitis, failure to respond
5
Q
Erysipelas
A
Most commonly affects elderly patients
- due to S. pyogenes
- characterized by erythematous plaque with sharply demarcated border
- mainly affects face and lower extremities
- possible prodrome of fever, chills, malaise
- lymph destruction may result in recurrent infections
- diagnosed via clinical presentation
- treated via Abx
6
Q
Erythrasma
A
Affects adult population
- caused by Corneybacterium minutissimum
- well-defined erythematous patches with fine scale
- involves axillae, inguinal folds, gluteal cleft, other moist sites
- generally asymptomatic
- diagnosed via Wood’s lamp exam w/ coral red fluoro
- treated with topical Abx or topical antifungals
7
Q
Tinea Corporis, Capitis, Pedis, Cruris
A
Tinea capitis (head) most common in children Tinea corporis (body), pedis (feet) and cruris (groin) more common in adults Tinea unguium (nails) aka onychomycosis common in adults
- caused by dermatophytes (trichophyton, epidermophyton, microsporum spp.)
- infections anthropophilic, zoophilic, or geophilic
- capitis: white scaling patches w/ hair loss
- corporis: erythematous, annular scaling plaques
- cruris: red, macerated patches in groin but not scrotum
- pedis: variable presentation in plantar area, redness, scale, vesicles, pustules, interdigital maceration
- unguium: yellow subungual hyperkeratosis/white scale
- diagnosed via KOH examination w/ branching hyphae and culture for capitis and onychomycosis
- treated with topical antifungals (clotrimazole, terbinafine)
8
Q
Pityriasis (tinea) versicolor
A
Infections usually after puberty, most common in YA
- caused by Malassezia furfur (yeast)
- transmitted via direct contact
- can be asymptomatic, macules and patches with fine, white, superficial scale –> scraping = more apparent
- pink in winter months (hypopigment in summer)
- diagnosed via KOH (spaghetti and meatballs)
- treated via antifungals, oral antifungals for extensive disease, wash skin twice monthly with selenium sulfide
9
Q
Cutaneous candidiasis
A
Most common in summer/high humidity and exacerbated in obesity as skin folds = moist, warm envi (diaper dermatitis)
- caused by Candida yeast
- presents Intertrigo (erythematous patches with satellite papules and pustules, maceration, foul odor, scrotum)
- diaper dermatitis: red papules and plaques with erosions
- diagnosed via KOH, revealing pseudohyphae (yeast)
- treated with topical antifungals (clotrimazole, nystatin), NOT terbinafine
- zinc oxide paste may help protect the skin against chronic maceration
10
Q
Seborrheic dermatitis
A
Affects infants
11
Q
Herpes simplex (HSV)
A
HSV1 - oral, HSV2 - genital disease
-high incidence of subclinical infection
- primary infection - first exposure to virus
- latent infection - virus travels retrograde to DRG (dormant until triggered by immunosuppression, stress, UV)
- secondary infection - same location as primary
- transmitted via direct contact and less commonly fomites
- prodrome of tingling sensation, painful uniform vesicles on red base which becomes eroded and crusted (scalloped borders), lymphadenopathy may occur, EM
- diagnosed by clinical presentation, Tzank prep (multinucleated giant cells), serologic test for Ab, culture (low sensitivity), PCR
- treated with oral antivirals (acyclovir) - must treat w/in 48 hrs of symptoms onset to reduce symptoms but no cure, crusted lesions no longer infectious
12
Q
Erythema multiforme (EM)
A
Recurrent, self-limited eruption of skin and/or oral mucosa
- may occur concurrently with clinical or subclinical HSV
- EM is rxn to underlying infection and HSV not present within skin lesions
- presents with targetoid macules
13
Q
Varicella zoster (VZV)
A
Shingles - affects pple who had chicken pox and are immunosuppressed
- malaise and vesicles on erythematous base ]
- risk of postherpetic neuralgia (chronic pain) among elderly and immunosuppressed
- virus travels retrogate to DRG
- immunosuppression allows virus to go back to skin
- prodrome of tingling and pain with dermatomal painful vesicles, lymphadenopathy may be present
- diagnosed via clinical + Tzank prep (multinucleated GCs)
- treated with oral antivirals + VZV vaccine
14
Q
Warts
A
Affects children and adults (lots of types of HPV)
- spread by direct contact
- HPV infects basal keratinocytes
- condyloma acuminata = warts affecting genital mucosae
- HPV 16, 18, 33, 35 risk for cervical cancer
- skin-colored papules with rough surface
- black dots represent thrombosed blood vessels
- flat warts with minimal scale vs. hyperkeratotic warts
- interuption of dermatoglyphs (fingerprints) ID residual
- diagnosed via clinical + acetowhite (vinegar) application + pap test
- treated via salicylic acid (daily), cryotherapy, immunotherapy, electrodessication and curettage, laser, HPV vaccine
15
Q
Molluscum contagiosum
A
Affects children and adults
-considered an STD among adults
- spread via direct contact
- asymptomatic skin-colored papule with umbilicated center
- rarely pruritic
- diagnosed via clinical presentation
- treated with cryotherapy, curettage, immunotherapy, but also resolves spontaneously
