American Society for Microbiology ABMM Answers

A Gram-positive rod is isolated from the blood culture of a neonate with sepsis. The organism exhibits weak beta-hemolysis on sheep blood agar, is catalase-positive, hydrolyzes esculin in the presence of bile, and demonstrates characteristic "tumbling" motility in a wet mount prepared from a broth culture incubated at 25° C. Which organism is most likely? 

A clinical microbiology laboratory is using flow cytometry to analyze lymphocyte subsets in a patient with suspected immunodeficiency. Which of the following cell surface markers is typically used to identify helper T cells?

During the investigation of a foodborne illness outbreak linked to raw sprouts, several bacterial isolates are obtained from patient stool samples and the implicated food source. Which of the following molecular methods would be MOST useful for establishing a definitive link between the clinical isolates and the food isolate?

Metagenomic analysis of a bronchoalveolar lavage (BAL) sample from a patient with severe pneumonia reveals a complex microbial community with a high abundance of both bacterial and fungal sequences. This approach is particularly useful in identifying:

A clinical laboratory performs a cefoxitin disk diffusion test on a Staphylococcus aureus isolate from a wound culture. The zone of inhibition measures 18 mm. According to current CLSI M100 guidelines, how should this result be interpreted regarding oxacillin/methicillin susceptibility?