Which genera of Enterobacteriaceae are usually nonmotile at 36°C?

The correct choice identifies genera of the Enterobacteriaceae family that are typically nonmotile at a temperature of 36°C.

Shigella, Klebsiella, and Yersinia are predominantly nonmotile. Shigella is particularly characterized by its inability to move independently, relying on other means for transmission. Klebsiella species also demonstrate nonmotility due to the absence of flagella. Similarly, Yersinia pestis, while it can be motile at lower temperatures, is nonmotile at 36°C, which is significant in clinical and laboratory settings.

In contrast, other choices involve genera that frequently have motile species. For instance, Escherichia and Enterobacter are known to exhibit motility, primarily due to the presence of flagella, while Salmonella is also motile. Understanding these motility characteristics is crucial for microbial identification and can help inform diagnostic approaches in microbiology.