American Board of Medical Microbiology

A clinical laboratory receives a cerebrospinal fluid (CSF) sample from a 65-year-old patient presenting with fever, headache, and nuchal rigidity. Gram stain reveals Gram-positive cocci in pairs and short chains.
Culture on blood agar grows alpha-hemolytic colonies that are optochin-susceptible and bile soluble.

Which organism is most likely identified?

A research laboratory is investigating the mechanisms of antiviral drug resistance. They are studying a herpes simplex virus strain that has developed resistance to acyclovir. The MOST common mechanism of acyclovir resistance in HSV involves mutations in the gene encoding:

A clinical microbiology laboratory is monitoring the emergence of resistance to colistin in Gram-negative bacteria. Resistance to colistin is often mediated by modifications of the bacterial lipopolysaccharide (LPS). The genetic basis for acquired colistin resistance most commonly involves:

A microbiology laboratory receives a blood culture from a patient with suspected bacterial endocarditis.
After 24 hours of incubation, Gram-positive cocci in clusters are observed on the Gram stain. Catalase test is positive, and coagulase test is negative. Further testing reveals susceptibility to novobiocin. The MOST likely organism is:

A centrifuge rotor containing capped tubes of sputum concentrate for AFB culture breaks during operation inside a Class II Biological Safety Cabinet (BSC).

What is the most appropriate immediate action for the technologist?

A researcher is investigating the mechanism of action of a novel antibacterial agent that inhibits bacterial protein synthesis. The agent binds to the 50S ribosomal subunit and prevents the translocation of peptidyl-tRNA.
This mechanism of action is similar to which of the following antibiotics?

A 55-year-old male with a history of poorly controlled diabetes mellitus develops a necrotizing fasciitis of his left lower extremity following a minor abrasion sustained while gardening. Initialcultures of the wound reveal a polymicrobial flora, including Gram-positive cocci in chains and Gram-negative bacilli. Over the next 48 hours, despite broad-spectrum antibiotic therapy, the patient's condition deteriorates, and new bullae with hemorrhagic fluid appear. Gram stain of this fluid now predominantly shows large, Gram-positive bacilli with subterminal spores.

Which of the following virulence factors is MOST likely contributing to the rapid tissue destruction observed in this patient?

Histopathological examination of lung tissue from an immunocompromised patient reveals large (8-15 ), spherical yeast cells with thick, refractile walls and characteristic single, broad-based budding. These findings are most suggestive of infection with:

Under the Clinical Laboratory Improvement Amendments (CLIA), participation in an approved external Proficiency Testing (PT) program serves primarily to:

An immunocompromised patient returning from a trip to the southwestern United States presents with fever, cough, and chest pain. Chest X-ray shows diffuse pulmonary infiltrates. Sputum culture grows a dimorphic fungus that forms spherules containing endospores at 37. The MOST likely causative agent is: