Yersinia pestis infection causes

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editors-In-Chief: Esther Lee, M.A.; Rim Halaby, M.D. [2]

Overview

Yersinia pestis (Y. pestis), a rod-shaped facultative anaerobe with bipolar staining (giving it a safety pin appearance) causes the infection in mammals and humans. The bacteria maintain their existence in a cycle involving rodents and their fleas. The genus Yersinia is gram-negative, bipolar staining coccobacilli, and, similarly to other Enterobacteriaceae, it has a fermentative metabolism. Y. pestis produces an antiphagocytic slime. The organism is motile when isolated, but becomes nonmotile in the mammalian host.

Taxonomy

Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacteriales; Yersinia; Yersinia pestis

Biology

Yersinia pestis, Direct Fluorescent Antibody Stain (DFA), 200x Magnification Courtesy: Public Health Image Library (PHIL), Centers for Disease Control and Prevention (CDC)

Photomicrograph of Yersinia (Pasteurella) pestis, sometimes referred to as Bacillus pestis. Courtesy: Public Health Image Library (PHIL), Centers for Disease Control and Prevention (CDC)

Yersinia pests is a nonmotile, non-spore-forming, Gram-negative, non-lactose fermenting, bipolar, ovoid, "safety-pin-shaped" bacillus.

Genome

The complete genomic sequence is available for two of the three sub-species of yersinia pestis: strain KIM (of biovar Medievalis), and strain CO92 (of biovar Orientalis, obtained from a clinical isolate in the United States). As of 2006, the genomic sequence of a strain of biovar Antiqua has been recently completed. Similar to the other pathogenic strains, there are signs of loss of function mutations. The chromosome of strain KIM is 4,600,755 base pairs long; the chromosome of strain CO92 is 4,653,728 base pairs long. Like its cousins Yersinia pseudotuberculosis and Yersinia enterocolitica, Yersinia pestis is host to the plasmid pCD1. In addition, it also hosts two other plasmids, pPCP1 (also called pPla or pPst) and pMT1 (also called pFra) that are not carried by the other Yersinia species. pFra codes for a phospholipase D that is important for the ability of Yersinia pestis to be transmitted by fleas. pPla codes for a protease, Pla, that activates plasminogen in human hosts and is a very important virulence factor for pneumonic plague. Together, these plasmids, and a pathogenicity island called HPI, encode several proteins that cause the pathogenesis, for which Yersinia pestis is famous. Among other things, these virulence factors are required for bacterial adhesion and injection of proteins into the host cell, invasion of bacteria in the host cell (via a Type III secretion system), and acquisition and binding of iron that is harvested from red blood cells (via siderophores). Yersinia pestis is thought to be descendant from Yersinia pseudotuberculosis, differing only in the presence of specific virulence plasmids.

A comprehensive and comparative proteomics analysis of Yersinia pestis strain KIM was performed in 2006. The analysis focused on the transition to a growth condition mimicking growth in host cells.