江苏部分地区食源性和人源沙门氏菌的多重耐药性研究

Characterization of multidrug-resistant Salmonella serovars isolated from meats and human samples in some regions of Jiangsu

从江苏省部分地区收集了117个沙门氏菌分离株,其中食物源和人源菌株分别有81株和36株。16种抗生素敏感性试验表明,有111个分离株对2种或2种以上的抗生素有耐药性,人源沙门氏菌分离株的抗生素耐药率比食物源的高,单一抗生素以链霉素耐药率(92.3%,108/117)最高。对5种或5种以上抗生素耐药的分离株有59株(50.4%),其中对特定六种抗生素:氨苄青霉素、氯霉素、链霉素、磺胺、四环素和卡那霉素耐药(ACSSuTK,R型)的菌株有12株。设计18对耐药基因和I类整合子保守区的引物,对36株有不同来源和耐药特征的多重耐药菌株进行耐药基因和I类整合子的检测,PCR扩增结果与抗生素敏感性表型一致。有30株细菌携带有I类整合子,大小为0.3、0.6、1.0、1.2和1.6kb,其中1.6kb(aadA5-dfr17)大小的整合子在25株细菌中分布(24/36)。接合试验表明,氨苄青霉素、氯霉素、链霉素、甲氧苄氨嘧啶和四环素的耐药特性是由接合性质粒携带。结果显示,耐药基因多数由I类整合子和质粒携带,可以通过接合试验发生转移,可移动的DNA成分可能在耐药特性的转移和分布中起到重要作用。

A total of 117 Salmonella strains isolated from retail meats and human in some regions of Jiangsu were assayed for their antimicrobial susceptibility, the presence of integrons and antimicrobial resistance genes, and the ability of horizontal transfer of the characterized antimicrobial resistance determinants via conjugation. 111 （94.9 % ） were resistant to at least two antimicrobial agents. Resistance against streptomycin 92.3% （108/117） was the most common. Whereas 59 （50.4%） were resistant to at least five antimicrobials. Twelve isolates showed resistance to six antimicrobials： ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, and kanamycin （R type ACSSuTK）. A total of 15 different antimicrobial resistance genes were identified in 36 muhidrug-resistant Salmonella isolates. While 30 （83 % ） of these isolates tested carried integrons ranging in size from 0. 3 to 1.6 kb. The most common integron was 1.6 kb which carried aadA5 and dfr17 gene cassettes. Conjugation studies demonstrated that there was plasmid-mediated transfer of antimicrobial resistance genes. These data showed that the Salmonella isolates recovered from meats and human in some regions of Jiangsu were commonly resistant to multiple antimicrobials, and genes conferring antimicrobial resistance in Salmonella were often carried on integrons and plasmids and could be transmitted through conjugation. The mobile DNA elements might played very important role in transmission and dissemination of antimicrobial resistance determinants among Salmonella strains.