耐药质粒介导宿主菌抵抗非特异性免疫应答的研究

Study on the Resistance to Non-Specific Immunity of the Host Bacteria Mediated by the Drug Resistant Plasmid

研究伤寒杆菌的耐药质粒pRST98是否能增强宿主菌的毒力 ,抵抗机体非特异性免疫应答———血清杀菌和巨噬细胞吞噬作用。 3株具有同源染色体的伤寒杆菌 (1)携带pRST98的野生型伤寒杆菌—STpRST98;(2 )经SDS人工消除pRST98的突变体菌株—ST (R ) ;(3)将pRST98重新导入突变体的接合子—pRST98/ST (R )菌株 ,用体外试验比较它们在人、兔及豚鼠 3种不同浓度、不同成分血清中的存活率 ,研究pRST98与血清杀菌试验中细菌抵抗力的关系。将荧光染料标记以上 3株细菌 ,用流式细胞术 (FCM )和标准系列稀释法检测它们被BALB/c小鼠腹腔巨噬细胞MΦJ774A 1吞噬和吞噬后在细胞内的存活情况。实验结果表明 ,携带pRST98的伤寒杆菌在血清中的抵抗力显著大于无此质粒的菌株 (P <0 0 5 ) ,被巨噬细胞吞噬的标记ST (R )菌量显著多于STpRST98和pRST98/ST (R ) ,但pRST98宿主菌在巨噬细胞内的活菌数却明显多于无此质粒的菌株 (P <0 0 5 )。说明pRST98不但能编码对药物的抗性 。

The aim of this study was to determine whether plasmid pR ST98 encoding resistance to antimicrobial agents in Salmonella typhi could mediate the resistance to non-specific immunity (serum bacteriocidal activity and phagocytosis by macrophages) of the host bacteria. Three chromosomally isogenic strains,that is,plasmid containing wild-type S.typhi STpR ST98,plasmid artificially cured by SDS ST(R -) and plasmid reintroduced into the cured strain pR ST98/ST(R -) were used to compare for their in vitro resistance to the bactericidal activity to human,rabbit and guinea pig serum. With a standard recovery procedure (log dilutions of lysed cells),the ability of survival within the macrophage MΦJ 774A.1 of BALB/c mouse of the three bacteria were compared,and the ability of resistance to phagocytosis of these three strains were further assayed by labeling and analysis of the bacterium-phagocyte interaction by flow cytometry. It was found that plasmid pR ST98 could mediate the resistance to serum bacteriocidal activity of its host bacteria,and also could enhance the ability of S.typhi to grow within the cells as determined by the macrophage survival test. More ST(R -) strains were phagocytosed by macrophages then STpR ST98 and pR ST98/ST(R -),but the numbers of viable bacteria of ST ST98 and pR ST98/ST(R -) were higher than that ST(R -).The results indicate that pR ST98 not only mediates drug resistance,but also resistance to non-specific immunity.