关键词: 鼠疫菌, 田鼠株, 鼠疫诊断噬菌体, 抗性, 动物实验, 布氏田鼠

Abstract: Objective To analyze the phenotype characteristics of Yersinia pestisMicrotus strain 90017 from Lasiopodomys brandtii, so as to provide a theoretical basis for investigating mechanisms of bacterial resistance to phages, the long-term preservation mechanisms of Y. pestis in plague foci, and evolutionary epidemiology of infectious diseases. Methods BALB/c mice were infected subcutaneously with 3 concentrations of Microtus strain of Y. pestis respectively including 2×10⁹,1×10⁶ and 1×10⁵ pieces /ml. Animals are dissected after death to isolated Y. pestis. It were observed on cultural characteristics and plague phage lytic test of Y. pestisMicrotus strain 90017. Result Y. pestis 90017 was cultured in a solid medium at 28°C for 24 hours before and after animal experiment, and it was found that the bacterial growth was slow. The bacterial colony showed typical morphology of Y. pestis after 48-100 hours of incubation. After a 24-hour bacteria lysed at 28°C in plague phage lysis test, the center of phage lysis zone demonstrated the appearance of broken glass and untypical debris of colonies. After 48-100 hours of incubation, in addition to the eroded residual colonies, some relatively complete colonies remained in the test zone where plague phage dripped and flowed through. The areas marked with the control Y. pestis strain 141 showed obvious bacterial lawn, and there was no bacterial growth in the areas where plague phage dripped and flowed through. The resulting phage lysis zone was wider than the trace left by the phage flow. The bacterium 90017 did not recover to its typical state after animal experiment, which was similar to its growth state and the result of plague phage lysis test for plague before animal experiment. Conclusion The coexistence of plague diagnostic bacteriophage-sensitive and -resistant strains in Microtus strain of Y. pestis 90017 from L. brandtii reflects biological complexity of microbial community in natural environment, which may play an important role in maintaining the epidemic and infection process of pestis.

Key words: Yersinia pestis, Microtus strain, Plague diagnostic phage, Resistance, Animal experiment, Lasiopodomys brandtii