Bacteriology Lab Exam - Fungi

Year 2 Semester 1

HX: opportunistic, white plaques (thrush), curd-like vaginal discharge, mastitis

Morphology: budding yeasts

What is it?

candida albicans

HX: chronic, antibiotic unresponsive bovine mastitis

What is it?

NOT BACTERIA; NOT FUNGI - Prototheca zopfii (ALGAE)

Classical association: bovine abortion (“mucormycosis”)

Histology: aseptate broad hyphae, irregular width, wide angle branching

Culture: fluffy mould on Sam

Microscopy: sporangium filled with sporangiospores

What is it?

Mucor species

class: zygomycetes aseptate fungi

Classical association: bovine abortion; nasal aspergillosis in dogs

Histology: septate, parallel walls, 45° dichotomous branching

Culture: powdery/velvety mould

Microscopy: conidiospores

What is it?

aspergillus fumigatus 

Clinical association: cats (pneumonia, CNS, nasal masses); most common systemic fungal pathogen in cats

Histology: soap bubble appearance due to the capsule

India ink: shows thick capsule

Culture: small, mucoid colonies

What is it?

Cryptococcus neoformas

Clinical association: NA dogs with coccidiodomycosis will have a history of travel to western USA or Mexico where this species is endemic

This stain is from a lung preparation from a dog

Has two forms – mould or yeast (aka thermally dimorphic fungi)

Mould form (25C): septate hyphae

Yeast/Spherule form (37C): huge spherules with endospores

What is it?

Coccidioides immitis 

Clinical association: systemic infection found in macrophages

Has two forms – mould or yeast (aka thermally dimorphic fungi)

Mould form (25C): septate hyphae, tuberculate chlamydospores

Yeast/spherule form (37C): small intracellular yeasts

Considered a Risk Group 3 fungal agent

What is it?

Histoplasma capsultatum

Commonly isolated from cases of otitis externa and dermatitis in dogs. It is thought to be an opportunist pathogen, since it may be found in low numbers, in the ears and on the skin of normal healthy dogs

gram stain smear of a case of chronic otitis externa in dog

 peanut/boot print/bowling ball shaped

What is it?

Malassezia pachydermatis

Clinical application: histology of canine with pneumonia, but can be in lungs (transtracheal aspirates), skin (exudates/aspirates), and brain (CSF)

Has two forms – mould or yeast (aka thermally dimorphic fungi)

Mould form (25C): septate hyphae

Yeast/spherule form (37C): large yeasts, thick wall, broad-based budding

Blastomyces dermatitidis 

Clinical associations: ringworm (dogs, cats = M. canis; cattle = T. verrucosum)

Histology (PAS): arthroconidia on/outside hair (ectothrix)(bring pink/red staining arthrospores called arthroconidia outside hair shaft)

KOH prep: clear keratin à reveals fungal arthrospores

Culture (SAB-CC): selective fro dermatophytes

Microscopy: M. canis = spindle macroconidia with terminal knob

What is it?

Microsporum canis (aka dermatophytes - ringworm)