Phenotypical characterization of Mongolian Yersinia pestis strains.

Although Mongolia is regarded as one of the possible places of plague radiation, only few data are available from Mongolian Yersinia pestis strains. In this study a total of 100 Mongolian Y. pestis strains isolated from wild mammals and their parasites between the years 1960 and 2007 were analyzed for their phenotype. All strains grew well on selective Cefsulodin-Irgasan-Novobiocin agar and were positive for the F1-antigen, the F1-gene (caf1), and the plasminogen activator gene (pla). Biochemical analyses using the API20E® system identified 93% of the strains correctly as Y. pestis. The BWY in-house system consisting of 38 biochemical reactions was used to differentiate among Y. pestis subspecies pestis biovars Antiqua and Medievalis and also between the subspecies microtus biovars Ulegeica and Caucasica. Antibiotic susceptibility testing according to Clinical and Laboratory Standards Institute-guidelines identified one strain as being multiresistant. This strain was isolated from a wildlife rodent with no anthropogenic influence and thus suggests naturally acquired resistance.