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…