Dr. Nancy Cornish Director of Microbiology Methodist and Children’s Hospitals CUTANEOUS INFECTIONS

Dermatophytoses (Ringworm, tinea) Pruritic, scaly, erythematous lesions with central clearing Common agents of infection –Epidermophyton floccosum –Trichophyton species –Microsporum species Topical or oral antifungal medications

Lab Diagnosis Cutaneous Fungal Infection –Lesion cleaned with 70% alcohol –Skin scrapings from active margin Scalpel or toothbrush –KOH prep, examine microscopically Rapid, inexpensive –Culture, if KOH negative Hold 4 weeks Can speciate, if necessary

Colorless (hyaline) branched septate hyphae “arthroconidia”

Calcofluor Stain

LAB Diagnosis Nails –Clean with 70% alcohol or soap and water –Clip nail back as far as possible and discard nail clippings –Obtain crumbling subungual debris from beneath trimmed nail edge with curette –KOH prep, examine microscopically –Culture, if KOH negative

LAB Diagnosis Hair –With forceps, collect 10 to 12 affected hairs with base of shaft intact, also collect scalp scales if present at active borders of lesions –Use of Wood’s lamp (UV light) can assist in selecting hair for culture as affected hair will usually fluoresce bright yellow-green –Submit for culture

Candidiasis Infects skin or mucous membranes (mouth, vagina) –Colonizer of normal hosts Skin - raw, moist, red with small satellite papules or pustules Mucous membranes - white moist patches with erythematous margin

Candidiasis Predisposing Conditions –Immunosuppression HIV Chemotherapy Steroids –Diabetes mellitus –Cutaneous maceration Groin, infra mammary folds Diaper area  Antibiotic treatment Vagina - vaginitis Mouth - thrush

Cutanous candidiasis

Thrush - Candida

Diaper rash - Candidiasis

Candidiasis LAB DX –Usually clinical diagnosis –If culture, then Candida screen –Selective fungal agar –Hold days Treatment –Oral antifungal agents –Topical antifungal ointments

Hyaline Branching Septate pseudohyphae with blastocondia and budding yeast

Tinea Versicolor (pityriasis) Due to lipophilic yeast; Malassezia furfur Faintly erythematous or hypopigmented macules with fine scale Involves torso, upper limbs Wood’s UV lamp will cause infected area to fluoresce; yellow-green If culture, requires lipid for growth (olive oil overlay).

Tinea versicolor

Tinea versicolor; rubbing lesion produces fine scale.

T. versicolor - buds through phialidic collerettes

T. versicolor; Spaghetti and meatballs

Erythrasma Chronic superficial bacterial skin infection of the stratum corneum Cause; Corynebacterium minutissimum Fine, scaly, reddish-brown macules or plaques Prefers toe webs, genitocrural areas Tx; Erythromycin

LAB Diagnosis: Erythrasma Wood’s lamp; coral red fluorescence due to porphyrin production Gram stain of skin surface scale shows many small pleomorphic gram positive bacilli, coccobacilli or filaments Culture rarely needed

Ulcers and Nodules and Sporotrichoid lesions

Ulcers Loss of epidermal and dermal layers

Nodules Inflammatory foci in which the most superficial cutaneous layers are intact

Sporotrichoid lesions Ulceronodular infection with lymphatic involvement  can travel up lymphatic vessels and create satellite lesions

Ulcers and Nodules Variety of bacteria and fungi cause these lesions Two mechanisms –Direct inoculation –Hematogenous dissemination

Organisms that cause ulcers or nodules or both after direct inoculation EXAMPLES: –Corynebacterium diphtheriae –Bacillus anthracis –Francisella tularensis –Nocardia species –Mycobacterium marinum –Sporothrix schenckii

Cutaneous diphtheria

F. tularensis; “tularemia”

M. marinum; swimming pool granuloma

Sporotrichosis

Malignant pustule of anthrax

Late stage anthrax

B. anthracis; non-hemolytic non-motile

Organisms that cause ulcers or nodules after hematogenous dissemination EXAMPLES: –Aspergillus species –Blastomyces dermatitidis –Cryptococcus neoformans –Mycobacterium tuberculosis

Sporotrichoid lesions These lesions begin as an ulcerated nodular lesion at the site of inoculation, primarily on the extremities, followed by development of subcutaneous nodules with overlying erythema and occasional ulceration proximally along lymphatics.

Sporotrichoid lesions EXAMPLES: –Sporothrix schenckii –Mycobacterium marinum –Norcardia spp.

Sporothrix schenckii Classic example of Sporotrichoid lesion Dimorphic soil fungus, rose bushes –Yeast phase at 37°C –Fungal hyphae phase at 25°C Gardeners, farmers, florists at risk