Opportunistic fungal infection
Dr Vishal KulkarniMBBS MD (Microbiology)
Opportunistic fungal infection
are those infections which are found in pts with underlying predisposing conditions. Malignancy Immunosuppressive therapyAIDSBurnDiabetesDialysis patients
Includes-
Candidiasis Cryptococcosis Aspergillosis Pneumocystosis Penicilliosis Zygomycosis Miscellaneous
Candidiasis• Yeast like spp causing mucocutaneous,
cutaneous and systemic infection.
• Caused by fungi of genus Candida.• Most pathogenic is Candida albicans.• Candida is component of normal flora.
• Commonly found on skin, g.i.tract, female genital tract during pregnancy.
• Clinical features1.Mucous membrane infections:
– Thrush (oropharyngeal)– Esophagitis– Vaginitis
2.Cutaneous infections:– Paronychia (skin around nail bed)– Onychomycosis (nails)– Diaper rash– Balanitis
Oral thrush Onychomycosis
3.Disseminated (systemic) infection:
– Endophthalmitis (eye), Liver and spleen, Kidneys , Skin, Brain, Lungs, Bone.
ENDOPHTHALMITIS DISSEMINATED SKIN LESION
• Laboratory diagnosis
– Specimens - Blood, urine, CSF, skin, respiratory secretions.
• A) Direct microscopy: - KOH mount, Gram stain
• Fungal culture:
– The specimen can be cultured on SDA with antibacterial antibiotics and incubated at 25°c & 37°c.
– Colonies are cream coloured,
smooth & pasty.
– Corn meal agar.
– CHROME agar
– TRM
• Germ tube formation: inoculation of
yeast in human serum incubated at 370C for 2 to 4 hours
Positive Negative
• Sugar assimilation and fermentation
• Serological reactions
- for Ag detection (ELISA, RIA, LA)
- for Ab detection (IF, ELISA)
• Molecular methods- PCR
• Treatment- Gentian violet, nystatin, amphotericin B,
azoles
CryptococcosisIs an infection caused by encapsulated
yeast belonging to genus cryptococcusVarieties
1. Cr. neoformans var. neoformans2. Cr. neoformans var. gattii3. Cr. neoformans var. grubii
Serotypes: A, B, C, D, ADOther spp-
- Cr. albidus- Cr. laurentii
• Habitat-– ubiquitous in nature– Pigeon droppings, nests, old buildings.
• Route of entry- inhalation, through skin• Males>females (age group- 30-50 yrs)• Clinical features-
– Lung, CNS, skin– Resp. pneumonitis– CNS – meningitis, meningoencephalitis– Cutaneous lesions– Bone infection
• Lab Diagnosis-• Specimens collection- CSF, Sputum,
exudates• Microscopy-
Direct examination: By India ink preparation-
Gram Stain- shows gram positive yeast cells
CFW, GMSHistopathology- sections stained with
H&E, PAS showing budding yeast cells.LCB- Encapsulated yeastCulture
- SDA- two slants at two temp (25˚& 37˚C)
- On SDA- mucoid, cream colored colonies
- On Birdseed agar- brown colonies
• Biochemical tests-– Urease positive– Assimilation of inositol & nitrate
• Ag detection-- Cryptolatex agglutination test- Titer- 1:8 or more is significant
• Ab detection-- Agglutination, Indirect fluorescence,
CFT• Animal Pathogenicity• PCR
Treatment-
- Amphotericin B, Fluocytosine
- Imidazole (miconazole,ketoconazole)
- Triazole (itraconazole, fluconazole, voriconazole)
- Echinocandins (caspofungin, micafungin)
AspergillosisIs a systemic & superficial fungal infection
caused by several species of the genus Aspergillus.
Three of them frequently encountered-- A. fumigatus- A. niger- A. flavus.
Source- ubiquitus in nature, soil, decaying plants.
Route of entry – through inhalation & through skin
• Clinical infections-– Lung infection
• Allergic aspergillosis• Aspergilloma• Invasive aspergillosis
– CNS infections– Keratomycosis– Paranasal sinus infections– Cutaneous infections– Endocarditis
Lab Diagnosis-Specimen collection -
sputum, BAL, transbronchial biopsy, pus, skin biopsy
Microscopy- KOH Prep- hyaline septate hyphae with
dichotomous branching.- CFW stain- fluorescence- Histopathological section-
- PAS, GMS stain- Acute angled (45˚) dichotomous branching
KOH Mount GMS
LPCB
• Fungal culture:- On SDA at 25°c & 37°c- Other media- PDA, Czepak-Dox agar, malt
extract
A. fumigatus A. niger A. flavus
Ag- Ab detection- Latex agglutination- ELISA, RIA, Immunoblotting
PCRSkin testTreatment-
- Amphotericin B- Voriconazole
Penicillium marneffei• Penicillium present in environment
various substrates like bread, jam, fruit & cheese.
• Are common airborne contaminant of culture media.
• Unique among penicillium, true pathogen & dimorphic.
• Causes skin lesions, disseminated infections in immunocompromised.
Lab Diagnosis-Microscopy
- Yeast are small, oval, 2-4 µm in diam.- Septate hyphae with branched
conodiophores- Two rows of sterigmata bearing chain of
spores (brush or brooms)
Culture-- On SDA-
- Mycelia forms produces red diffusable pigment
Treatment-- IV amphotericin B- oral itraconazole
ZygomycosisCaused by aseptate filamentous fungi1. Mucormycosis
- Rhizopus arrhizus- Mucor racemosus- Absidia corymbifera- Cunninghamella spp- Apophysomyces spp
2. Entomopthormycosis- conidiobolus spp.- basidiobolus spp.
Clinical features-
• Rhinocerebral zygomycosis
• Pulmonary zygomycosis
• Cutaneous zygomycosis
• GIT zygomycosis.
• Disseminated zygomycosis
Peculiar characterstics-
- broad aseptate hyphae- predilection to involve blood vessle- diabetes is a risk factor
Diagram of morphology-
Lab diagnosis-Specimen collection -
- nasal discharge, pus, sputum, biopsy.Microscopy-
- KOH prep & biopsy with H&E- Broad, aseptate, ribbon like hyphae - branching at 45-90˚ angles.
Culture- - Two SDA at 25˚ & 37˚C
Colony characters & LCB picturesFungus Colony LCB PictureMucor Gray Brown Branched sporangiophores,
rhizoids absentRhizopus Light to dark
grayDistinct rhizoids, below sporangiohores, ovoid collumella
Absidia white to pale gray
Rhizoids present in between, pear shaped collumella,
Mucor Rhizopus Absidia
Treatment-- IV amphotericin B
- Surgical drainage
- Good medical control of diabetes
PneumocystosisCaused by Pneumocystis carinii OR
Pneumocystis jirovacii.Previously thought to be protozoa.Has three forms-
- Cyst- Sporozoites- Trophozoites
Clinical features-- Primary atypical pneumonia.- Extrapulmonary pneumocystosis
Lab Diagnosis-- Specimen collection
- BAL, Induced sputum, - Tissue biopsy
- Microscopy- GMS – masses of black coloured cysts- Giemsa – reddish nucleus with blue cytoplasm
Giemsa
GMS
- Gram Weigert stain- CFWCulture- not usefulPCR, DNA probes
Treatment- Septran, Pentamidine isethionate for acute cases- Septran for prophylaxiss
Miscelleneous opportunistic mycoses
- Trichosporonosis (haemato+ CNS)
- Geotrichosis (Pulmonary)
- Blastoschizomyces infection (onychomycosis)
- Rhodotorula infection (disseminated)
Thank you…
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