ABSTRACT
Plesiomonads are rod-shaped, gram-negative, facultative anaerobic, oxidase- and catalase-positive, flagellated bacteria emerging as important effectors in foodborne diseases. Plesiomonas shigelloides—the only currently known species of the Plesiomonas genus—is a waterborne ubiquitous Enterobacteriaceae that presents Shigella-like antigens but striking diverging structural and biochemical characteristics from its family. This bacterium is capable of adapting to different substrate and environmental conditions and, consequently, has been isolated from several sources, including freshwater and its inhabitants, seawater, fresh vegetables, and domestic animals. In humans, plesiomonads have been historically regarded as gastroenteric opportunistic pathogens typical of tropical ecosystems, and their infections often come secondary to other diseases. Moreover, the most common complications caused by this microorganism are minor gastrointestinal affections and usually self-resolving. However, P. shigelloides is gaining attention recently, as there are increasing reports of mild and severe gastrointestinal and extraintestinal pathologies with plesiomonads as the main causative agent and can be a serious threat to immunocompromised hosts.
