CUTANEOUS INFECTIONS

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CUTANEOUS INFECTIONS
Dr. Nancy Cornish Director of Microbiology Method
ist and Childrens Hospitals
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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

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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

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Colorless (hyaline) branched septate hyphae
arthroconidia
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Calcofluor Stain
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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

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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 Woods lamp (UV light) can assist in
  selecting hair for culture as affected hair will
  usually fluoresce bright yellow-green
• Submit for culture

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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

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Candidiasis

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

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Cutanous candidiasis
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Thrush - Candida
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Diaper rash - Candidiasis
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Candidiasis

• LAB DX
• Usually clinical diagnosis
• If culture, then Candida screen
• Selective fungal agar
• Hold 5 - 7 days
• Treatment
• Oral antifungal agents
• Topical antifungal ointments

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Hyaline Branching Septate pseudohyphae with
blastocondia and budding yeast
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Tinea Versicolor (pityriasis)

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

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Tinea versicolor
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Tinea versicolor
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Tinea versicolor rubbing lesion produces fine
scale.
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T. versicolor - buds through phialidic collerettes
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T. versicolor Spaghetti and meatballs
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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

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LAB Diagnosis Erythrasma

• Woods 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

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Ulcers and Nodules and Sporotrichoid lesions
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Ulcers

• Loss of epidermal and dermal layers

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Nodules

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

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Sporotrichoid lesions

• Ulceronodular infection with lymphatic
  involvement
• ?can travel up lymphatic vessels and create
  satellite lesions

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Ulcers and Nodules

• Variety of bacteria and fungi cause these lesions
• Two mechanisms
• Direct inoculation
• Hematogenous dissemination

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Organisms that cause ulcers or nodules or both
after direct inoculation

• EXAMPLES
• Corynebacterium diphtheriae
• Bacillus anthracis
• Francisella tularensis
• Nocardia species
• Mycobacterium marinum
• Sporothrix schenckii

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Cutaneous diphtheria
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F. tularensis tularemia
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M. marinum swimming pool granuloma
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Sporotrichosis
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Malignant pustule of anthrax
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Late stage anthrax
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B. anthracis non-hemolytic non-motile
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Organisms that cause ulcers or nodules after
hematogenous dissemination

• EXAMPLES
• Aspergillus species
• Blastomyces dermatitidis
• Cryptococcus neoformans
• Mycobacterium tuberculosis

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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.

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Sporotrichoid lesions

• EXAMPLES
• Sporothrix schenckii
• Mycobacterium marinum
• Norcardia spp.

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Sporothrix schenckii

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