屠宰肉沙门菌血清型鉴定及CTX-M型ESBLs的流行调查

Serotype identification and prevalence of CTX-M ESBLs among Salmonella from raw meat in slaughterhouse

本研究收集了2015-2017年分离自屠宰肉(鸡肉、猪肉和鸭肉)的110株沙门菌,采用MALDI-TOF/TOF质谱微生物鉴定系统和分子生物学方法进行菌株鉴定。采用二倍琼脂稀释法测定沙门菌对兽医临床常用17种抗生素的敏感性;玻片凝集法进行血清型鉴定;PCR及基因测序方法检测沙门菌CTX-M型ESBLs耐药基因的流行以及所携带的其他耐药基因。结果显示,110株沙门菌对一些常用药物,如四环素、萘啶酸以及氨苄西林耐药率高达75%以上,对第三代头孢菌素的耐药率为20%~30%,对氟喹诺酮类耐药率接近40%,对阿米卡星的耐药率较低为5%。110株沙门菌共鉴定出15种血清型,以鼠伤寒(24%)和印第安纳型(23%)为主,其次为里森(16%)、德尔卑(8%)、肠炎(8%)以及一些不常见血清型。110株沙门菌中共检出19株CTX-M型阳性菌株,共有4种不同亚型,优势CTX-M亚型为blaCTX-M-55共12株、4株blaCTX-M-27、2株blaCTX-M-65、1株blaCTX-M-64,12株产CTX-M-55的沙门菌中携带有至少1种以上的PMQR基因,且都发生gyrA:S83F D87G+parC:T57S S80R多靶位突变。产CTX-M-55沙门菌对氟喹诺酮类药物表现出高水平耐药,且都携带有至少2种以上的PMQR基因,这种对头孢菌素和氟喹诺酮类耐药的菌株随着食物链传播和扩散,对公共卫生和人类健康都存在潜在风险。

A total of 110 Salmonella isolates from raw meat in slaughterhouse between 2015 and 2017 were recruited in this study.All Salmonella isolates were confirmed by MALDI-TOF MS and amplification of invA gene specific for Salmonella.Susceptibility of 110 Salmonella to 17 antimicrobials were performed using the agar dilution method.The serotype was identified by slide agglutination method.The prevalence of CTX-M ESBLs resistance gene and other drug resistance genes were investigated by PCR and sequencing.The resistance rate of 110 isolates to commonly used drugs,such as tetracycline,nalidixic acid and ampicillin,was as high as 75%,the resistance rate to third-generation cephalosporins was 20%-30%,resistant rate to fluoroquinolones was nearly 40%,The resistance rate to amikacin was lower,at 5%.A total of 15 serotypes were identified from 110 isolates,mainly typhimurium(24%)and Indiana(23%).A total of 19 CTX-M positive strains were detected in 110 Salmonella,including four different subtypes.The dominant CTX-M subtype was blaCTX-M-55,with 12 strains in total,4 in blaCTX-M-27,2 in blaCTX-M-65,and 1 in blaCTX-M-64.12 CTX-M-55 producers were detected carrying at least one PMQR gene,and harboring multiple mutations in target gene(gyrA:S83 FD87 G+parC:T57 SS80 R).The spread and dissemination of such strains harboring genes conferring resistance to cephalosporins and fluoroquinlones imposed potential risk to public health.