PHOSPHOLIPASE-A OF YERSINIA-ENTEROCOLITICA CONTRIBUTES TO PATHOGENESIS IN A MOUSE MODEL

Some isolates of Yersinia enterocolitica exhibit phospholipase activit y, which has been linked to lecithin-dependent hemolysis (M. Tsubokura , K. Otsoki, I. Shimohira, and H. Yamamoto, Infect. Immun. 25:939-942, 1979). A gene encoding Y. enterocolitica phospholipase was identified , and analysis of the nucleotide sequence revealed two tandemly transc ribed open reading frames, The first, yplA, has 74% identity and 85% s imilarity to the phospholipase A found in Serratia liquefaciens. Thoug h the other, yplB, was less similar to the downstream accessory protei n found in S. liquefaciens, the organization in both species is simila r. Subsequently, a yplA-null Y. enterocolitica strain, YEDS10, was con structed and demonstrated to be phospholipase negative by plate and sp ectrophotometric assays. To ascertain whether the phospholipase has a role in pathogenesis, YEDS10 was tested in the mouse model. In experim ents with perorally infected BALB/c mice, fewer YEDS10 organisms were recovered from the mesenteric lymph nodes and Peyer's patches (PP) tha n the parental strain at 3 or 5 days postinfection, Furthermore, bowel tissue and PP infected with YEDS10 appeared to be less inflamed than those infected with the parental strain. When extremely high doses of both the parental and YEDS10 strains were given, similar numbers of vi able bacteria were recovered from the PP and mesenteric lymph nodes on day 3, However, the numbers of foci and the extent of inflammation an d necrosis within them were noticeably less for YEDS10 compared to the parental strain, Together these findings suggest that Y. enterocoliti ca produces a phospholipase A which has a role in pathogenesis.