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Cutaneous infections and
AIDSThe pathogens involved and
their detection
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Pathogens involved:
VirusesFungi
Bacteria
Parasites
Arthropod
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HIV/AIDS
mucocutaneous
infections
H.Schoefer
1998 (%)
N=330
Kumarasamy
2000 (%)
N=833
Oral Hairy leukoplakia 45.0 2.3
Oral Candidiasis 15.8 (Candidiasis 45.0
Seborrheic dermatitis 40.3 ----------Dermatophytes 30.6 8.0
Staph infections 30.3 (folliculitis) 2.9
Herpes genitalis 25.8 7.7
Herpes Zoster 21.2 11.2
Pyoderma 18.2 ---------
Molluscum contagiosum 1.3 26.0
Scabies --------------- 0.5
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Viruses
Herpes Zoster infection - HZV
Herpes labialis, anogenital Herpes - HSV
Molluscum contagiosum - Pox virus (DNA)
Warts - HPV
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Clinical appearance:
Molluscum contagiosum
Warts
Diagnosis
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HSV or HZV Lab diagnosis;
Viral culture most sensitive clinicalmethod Culture sensitivity is higher when the herpetic
vesicular lesions first appear and before they ulcerateLater ulcerative lesions may have no detectable virus.
Antigen detection less sensitive.
Serologic testing (antibodies)for detection
of past infection not acute infection, Immunocompromised patients unlikely to mount
a significant (fourfold or greater) rise in anti-HSVtitre between acute and convalescent samples.
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Viruses typically appear as geometric arrays of
spherical particles
Herpes viruses - electron micrograph
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Bacteria:
Staphylococcus infections
Folliculitis
Boils (Furuniculosis)
Pyoderma
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Diagnosis of Staphylococcus aureusinfections
Specimen - swab in transport medium
Gram stain - Gram positive cocci
Culture Sheeps blood agar
Identification: Gram + coagulase test +DNase
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Scabies: Sarcoptes scabeiDiagnosis:Look for - presence of burrows or rash
at site of infection- mites, eggs, mite faecal matterin Skin scraping
Parasite
Egg
Mite
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Superficial Fungal infections
Dermatophyte infectionsCandidiasis
?Seborrheic dermatitis
Superficial manifestations of systemic infection:
Histoplasmosis
Cryptococcosis
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Candida infections appropriate specimen
Onychomycosis
Specimen:
Scraping or
Clipping
Interdigital
CandidiasisSpecimen:Scraping
OralCandidiasis
Specimen:
Swab
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Lab Diagnosis of Candidiasis
MicroscopySwab
Smear
Gramstain/PAS
Pseudohyphae+blastospores
Skin scrape10% KOH
Preparation
Candida species
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Lab Diagnosis of Candidiasis
Culture on Sabouraud dextrose agar+chloramphenicol. Incubate at 37C
Gram stain, germ tube test,chlamdospore production,
Carbohydrate assimilation
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Lab Diagnosis of Dermatophyte infections
Tinea pedis
Tineacorporis Tinea unguium
Tinea capitis
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Lab Diagnosis of Dermatophyte infections
Specimen Clippings or scrapings
Nail scrapings and clippings on black paper
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Lab Diagnosis of Dermatophyte infections
Microscopy:
10or 30% KOH preparation
Hair invasion
Ectothrix
Endothrix
Fungal hyphae+ arthrospores
Skin
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Lab Diagnosis of Dermatophyte infections
Culture on Sabouraud dextrose agar+ chloramphenicol+cycloheximide Incubate at 25C
Trichophytonrubrum
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Cryptococcosis
Cryptococcus neoformans (Filobasidiellaneoformans)
Varieties Serotypes Main geographic
distributionneoformans D Northern Europe
gattii B,C* Tropical + sub tropical
grubii A* World-wide
Source: pigeon droppings (A,D), gum trees (B,C)
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Cryptococcus neoformans in india inkpreparation shows importantidentification features
Carbohydratecapsule
Cell wall
Cell contents
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AIDS associated cryptococcal infection May present with severe progressive
pneumonia + acute dyspnoea
Disseminated cutaneous lesions pustular + papular, nodular, ulceratedlesions
Meningitis
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Specimens to diagnose cryptococcal
infectionSputum
Bronchoalveolar lavage
Transbronchial biopsyBlood culture
BiopsyUrine C. neoformans is aClass 2 Pathogen
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Detection methods Microscopy 10%KOH + india ink preparations
Culture Chocolate agarSabouraud dextrose agar
chloramphenicol
Niger seed agar
Serology to detect Ab and capsular antigen
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Cryptococcus neoformans in india ink
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Culture characteristics
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Latex particle agglutination test Latex particles coated with Ab to carbohydrate capsule Agglutinates in presence of Antibody Specimens:
Serum, CSF, urine, BAL, aspirate
Sensitivity 75-100% Specificity 90-100%
False positives:Rheumatoid factor
KlebsiellaSyneresis fluidSome soaps, disinfectants
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India ink
Culture + antigen test Culture
+
+ve
+ve
- ve
Summary C.neoformans lab diagnosis
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Histoplasmosis
Histoplasma capsulatum (Ajellomyces capsulatus)
Dimorphic fungus
37C 25C
Yeast phase Filamentous phase+Infection Macroconidia
Microconidia
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Histoplasma capsulatum
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Clinical Features1. Primary lung infection
Sub-acute/acute (caves disease)
Flu-like illness usually self-limiting
Acute pneumonia2. Chronic cavities
3. Disseminated from lung RES Wt. LossFever
Liver,spleenUlcers mouthSkin lesions
Severe acute pneumonia
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Specimens
Sputum BAL
Lymph nodes Liver biopsy
Blood Bone marrow Urine
Biopsy from skin lesions
H.capsulatum is aClass 3 pathogen
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Tests available
Microscopy
Culture
SerologyPCR
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H.capsulatum - PAS stain
Smallintracellularyeast cells
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H. capsulatum
Cultures
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H. capsulatum
Yeast phase - 37C
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H.capsulatum
Macro and micro-conidia - 25C
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Comparison of sensitivities of different diagnostictest for disseminated histoplasmosis in patients
with AIDS
J.Wheat Clin.Microbiol Rev 1995
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Diagnostic tests are available in Zimbabwe?
Microscopy Gram. India ink, KOHCultureCryptococcal antigen test
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