Yersinia

Yer.si' ni.a . M.L. fem. n. Yersinia named for the French bacteriologist A.J.E. Yersin, who first isolated the causal organism of plague in 1894. Proteobacteria / Gammaproteobacteria / Enterobacteriales / Enterobacteriaceae / Yersinia Straight rods to coccobacilli , 0.5–0.8 × 1–3 µm. Endospores are not formed. Capsules are not present, but an envelope occurs in Y. pestis strains grown at 37°C and in cells from clinical sources. Gram negative, nonmotile at 37°C, but motile with peritrichous flagella when grown below 30°C, except for Y. pestis , which is always nonmotile . Growth occurs on ordinary bacteriological media. Colonies of yersiniae are translucent to opaque, 0.1–1.0 mm in diameter after 24 h. Optimum growth temperature, 28–29°C. Facultatively anaerobic, having both a respiratory and a fermentative type of metabolism. Oxidase negative. Catalase positive. Nitrate is reduced to nitrite with a few exceptions in specific biovars. D ‐glucose and other carbohydrates are fermented with acid production but little or no gas. Phenotypic characteristics are often temperature dependent, and usually more characteristics are expressed by cultures incubated at 25–29°C than at 35–37°C . The enterobacterial common antigen is present in all species investigated. Widely distributed in nature with some species adapted to specific animal hosts and humans. Several species are pathogenic for humans and animals including Y. pestis , the causative agent of plague. A significant cause of food‐borne and waterborne disease. Belongs to the Gammaproteobacteria . The mol % G + C of the DNA is : 46–50. Type species : Yersinia pestis (Lehmann and Neumann 1896) Van Loghem 1944, 15 ( Bacterium pestis Lehmann and Neumann 1896, 194; Yersinia pseudotuberculosis subsp. pestis Bercovier, Mollaret, Alonso, Brault, Fanning, Steigerwalt and Brenner 1981a, 383.)