Medical Laboratory Scientist ASCP Practice Exam 2025 – Complete Study Guide

Shigella species are a group of bacteria known for their lack of motility, distinguishing them from other similar organisms. Unlike many enteric bacteria, Shigella does not possess flagella and therefore does not exhibit motility. This non-motility is a fundamental characteristic that helps in identifying and differentiating Shigella from other pathogens, such as Escherichia coli, which can be motile.

Additionally, Shigella is associated with causing gastroenteritis and dysentery, where it invades the epithelial cells of the intestinal mucosa, leading to severe inflammation and ulceration. Understanding that Shigella is non-motile is crucial in diagnostic microbiology and helps laboratory personnel accurately identify and report its presence in clinical specimens.

In contrast, the presence of Gram-positive cocci would imply a completely different type of bacteria, such as Staphylococcus or Streptococcus, while highly motile organisms are typically associated with genera like Salmonella or E. coli. Spores formation is characteristic of certain Gram-positive bacteria like Bacillus or Clostridium, which is also inconsistent with the characteristics of Shigella.