fungi to dx

Question 1

Histoplasma capsulatum
blastomyces dermatitidis
coccidioides immitis

Answer 1

o Antigenic preperations called coccidiodin and histoplasmin can be checked in the same way PPD is in the skin to check for previous exposure, but most people have been exposed before and will not be very helpful.
o Biopsy of the affected tissue (lung, skin, etc), culture on Sabouraud’s or blood agar, and examination with silver stain.
o serologic tests like complement fixation and latex agglutination.
o urine Histoplasma ag test.

Question 2

malassezia furfur. (Pityriasis versicolor (tinea versicolor))
exophilia werneckii. (Tinea nigra )

Answer 2

KOH slide w skin scrapings to look for hyphae and spherical yeast,
o Malassezia look like like spaghetti

Question 3

Dermatophytoses

Answer 3

• Take skin scrapings, digest the keratin with KOH and look for the presence of branched hyphae.
• Directly examine the hair or nails with wood’s light (UV 365nm): Some species of microsporum will fluoresce a brilliant green

Question 4

Phialophora and cladosporium

Answer 4

Skin scrapings and KOH show copper-colored sclerotic bodies.

Question 5

sporotrichosis from Sporothrix schenckii

Answer 5

Culture at 37 to find yeast, while culture at 25 shows branching hyphae (dipmorphism)

Question 6

canadidasis from canadidia albicans in immnocomprimised ppl

Answer 6

-Normal flora that can be found in most places/secretions of the body, but never normal in the blood.
-Cultures are the gold standard.
• Use KOH on skin scrapings or biopsies of tissue.
• Blood test for beta-D-glucan (from fungal cell wall).
• T2Candida assay: looks for amplified DNA using magnetic resonance technology and PCR assay

Question 7

cryptococcosis from Crytococcus neoformans and Cryptococcus gattii

Answer 7

o CSF india ink stain shows yeast cells with surrounding halo (the capsule), but only works half the time.
o Better test is to look for the cryptococcal atgs and confirm with culture.