Superficial and Systemic Mycoses MCQs

Taxonomical Classification - Based on the production of sexual spores, the Kingdom Fungi has been divided into four medically important phyla. They are as follows: Phylum zygomycota: They are lower fungi, produce sexual spores known as zygospores and possess aseptate hyphae, e.g. Rhizopus and Mucor Phylum ascomycota: They produce sexual spores known as ascospores and possess septate hyphae, e.g. Aspergillus Phylum basidiomycota: They produce sexual spores known as basidiospore e.g. Cryptococcus Phylum deuteromycota (Fungi imperfecti): In majority of the medically important fungi, the sexual state is either absent or unidentified yet. Hence, they are traditionally grouped as fungi imperfecti. Reference : Sastry 3rd ed pg. 116 Reference : Ananthnarayan and Paniker's textbook of Microbiology 12 th edition pg no. 87

Cultures of Coccidiodes are highly infectious; may lead to accidental inhalation of spores in laboratories and hence require biosafety level-3 precautions Reference : Sastry 3rd Ed pg. 382 Reference : Ananthnarayan and Paniker's textbook of Microbiology 12 th edition pg no. 413

Ans. is 'd' i.e. T. mentagrophytes Zoophilic dermatophytes are the species which primarily infect animals and occasionally transmitted to humans. Zoophilic species of trichophyton are T. montegrophytes and T verrucosum. Other zoophilic species of dermatophytes is M. canis.

SDA (Sabouraud dextrose agar): It is the most commonly used medium in diagnostic mycology. It contains peptone 1%, dextrose 4% and has a pH of 5.6. This may not support some pathogenic fungi. Neutral SDA (Emmons modification): It differs from the original SDA in having neo peptone 1% and dextrose 2% with a pH of 7.2. Reference: Essentials of Medical Microbiology by Apurba Sastry and Sandhya Bhat, 3rd Edition, Page Number-117.

They exist as molds (hyphal form) in the environment at ambient temperature (25°C) and as yeasts in human tissues at body temperature (37°C). Examples Histoplasma capsulatum Blastomyces dermatitidis Coccidioides immitis Paracoccidioides brasiliensis Talaromyces marneffei Sporothrix schenckii. Reference : Sastry 3rd ed chapter 6 Reference : Ananthnarayan and Paniker's textbook of Microbiology 12 th edition pg no. 86

Malassezia furfur is lipophilic, SDA with olive oil overlay is the ideal media for culture. Typical 'fried egg' colonies appear after incubating for 5-7 days at 32-35° C. Since it is lipophilic, patient receiving total parental nutrition are more susceptible. Reference : Sastry 3 rd edition pg. 575 Reference : Ananthnarayan and Paniker's textbook of Microbiology 12 th edition pg no. 599