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Microbiology Flashcards

6 cards from real ASCP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Viridans streptococci cause which serious infection by colonizing damaged heart valves?

    Answer: Bacterial endocarditis

    Viridans streptococci are the most common cause of subacute bacterial endocarditis, particularly in patients with pre-existing valvular disease.

  2. Which parasite is identified by finding trophozoites with ingested red blood cells in stool?

    Answer: Entamoeba histolytica

    Entamoeba histolytica trophozoites actively ingest red blood cells (erythrophagocytosis), a pathognomonic finding in stool.

  3. The KOH preparation of skin scrapings showing hyphae and yeast ('spaghetti and meatballs') is diagnostic of:

    Answer: Tinea versicolor (Malassezia furfur)

    Malassezia furfur, the cause of tinea versicolor, produces characteristic short hyphae and round yeast cells resembling spaghetti and meatballs.

  4. Stool culture for cholera (Vibrio cholerae) uses which selective medium?

    Answer: TCBS (thiosulfate-citrate-bile salts-sucrose) agar

    TCBS agar selects for Vibrio species; V. cholerae ferments sucrose producing yellow colonies on this medium.

  5. Which test is used to detect penicillin susceptibility differences between S. pneumoniae isolates?

    Answer: 1-µg oxacillin disk diffusion or MIC testing

    The 1-µg oxacillin disk screens for penicillin-non-susceptible pneumococci; MIC testing then determines exact susceptibility categories.

  6. Which organism forms germ tubes when incubated in serum at 37°C for 2–3 hours?

    Answer: Candida albicans

    Candida albicans (and C. dubliniensis) form germ tubes (pseudohyphae beginnings) in serum at 37°C, a rapid presumptive identification test.