American Society of Microbiology ABMM Sample Questions:

1. A clinical microbiology laboratory is performing antimicrobial susceptibility testing on a Streptococcus pneumoniae isolate recovered from a patient with meningitis. The isolate shows reduced susceptibility to penicillin (MIC = 2 µg/mL). The MOST likely mechanism for this reduced susceptibility is:

A) Increased activity of efflux pumps that actively remove penicillin from the cell.
B) Production of beta-lactamase enzymes that hydrolyze penicillin.
C) Modification of the peptidoglycan structure, preventing penicillin binding.
D) Alterations in the penicillin-binding proteins (PBPs) that reduce their affinity for penicillin.

2. A clinical microbiology laboratory is using a nucleic acid amplification test (NAAT) to detect Mycobacterium tuberculosis directly from sputum. A positive result indicates:

A) Drug susceptibility information for the M. tuberculosis strain.
B) Active tuberculosis disease requiring immediate treatment.
C) The presence of viable M. tuberculosis organisms.
D) The presence of M. tuberculosis DNA, which could be from viable or non-viable organisms.

3. During an outbreak of norovirus gastroenteritis in a nursing home, environmental swabs are collected to identify the source of the infection. Which of the following methods would be MOST appropriate for detecting norovirus in these samples?

A) Reverse transcription-polymerase chain reaction (RT-PCR)
B) Culture on human embryonic kidney (HEK) cells
C) Gram staining and microscopy
D) Enzyme-linked immunosorbent assay (ELISA) for viral antigens

4. A patient with a history of chronic lung disease develops a severe pneumonia. Bronchoalveolar lavage fluid reveals the presence of numerous cysts containing multiple nuclei, which stain positively with silver stains but poorly with Gram stain. The patient's CD4+ T-cell count is within the normal range. The MOST likely causative organism and the preferred treatment are:

A) Paragonimus westermani; praziquantel.
B) Histoplasma capsulatum; amphotericin B followed by itraconazole.
C) Blastomyces dermatitidis; itraconazole.
D) Pneumocystis jirovecii; trimethoprim-sulfamethoxazole.

5. A diagnostic laboratory is validating a new multiplex PCR panel for respiratory pathogens. According to CLIA regulations, which of the following parameters must be established by the laboratory performing the validation for this qualitative nucleic acid amplification test?

A) Accuracy, Precision, Reportable Range, Analytical Sensitivity
B) Accuracy, Precision, Clinical Sensitivity, Clinical Specificity
C) Accuracy, Precision, Analytical Sensitivity, Analytical Specificity (including cross-reactivity)
D) Precision, Reportable Range, Analytical Specificity, Reference Interval

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