河南省猪产业链中耐头孢菌素沙门菌对β-内酰胺类和喹诺酮类药物的耐药机制分析

Analysis of mechanisms of resistance to β-lactams and quinolones for cephalosporin-resistant Salmonella isolates from pig-borne food chain of Henan Province

对河南省猪产业链中分离的28株耐头孢菌素沙门菌进行血清学分型、药敏试验和超广谱β-内酰胺酶(ESBLs)筛查,并进一步采用PCR扩增和DNA测序检测β-内酰胺基因、喹诺酮类耐药基因以及喹诺酮类耐药决定区(QRDR)氨基酸突变。结果显示,河南省猪产业链中耐头孢菌素沙门菌的流行率为0.89%(28/3 137),其中肝脏样品流行率最高(4.98%,16/321);28株检测菌,共分为7种血清型,主要血清型为印第安纳(46.43%,n=13)和单相鼠伤寒变种(25%,n=7)。所有菌株除了黏杆菌素,对其他11种药物耐药率均高于60%,多重耐药率为100%;至少携带1种β-内酰胺酶基因,携带率最高的基因是blaCTX-M(89.29%,n=25),共携带有6种组合的β-内酰胺酶基因谱;共检测到4种喹诺酮类耐药基因(aac(6)-Ib-cr、oqxAB、qnrS和qnrC),gyrB和parE均无氨基酸突变,其中15株菌同时发生gyrA(Ser83Phe与Asp87Asn/Gly)突变和parC(Thr57Ser与Ser80Ile/Arg)突变,无论是否存在喹诺酮耐药基因,对环丙沙星均呈高水平的耐药(MIC≥16 mL/L)。结果表明,河南省猪产业链中耐头孢菌素沙门菌的流行率相对较低,对多种药物均具有严重的耐药性,对β-内酰胺类药物、氟喹诺酮类药物的耐药表型与其耐药基因型一致。

This study aimed to investigate mechanisms of resistance to β-lactams and quinolones for 28 cephalosporin-resistant Salmonella isolates from pig-borne food chain of Henan Province.Serotyping,antimicrobial susceptibility testing and extended-spectrum β-lactamases(ESBLs) were performed;the presence of β-lactamase genes,plasmid-mediated quinolone resistance genes and amino acid mutations in the quinolone resistance-determining region(QRDR) was detected by PCR amplification and sequencing.The results showed that the prevalence rate of cephalosporin-resistant Salmonella isolates was 0.89%(28/3 137) in all samples from pig-borne food chain of Henan Province,with the highest prevalence in liver samples(4.98%,16/321).All Salmonella isolates were classified into 7 serotypes,and the main serotypes were Indiana(46.43%,n=13) and monophasic Salmonella typhimurium(25%,n=7).Except for colistin,the resistance rate of all strains to other 11 drugs was higher than 60%,and the multi-drug resistance rate was 100%.All the isolates tested carried at least oneβ-lactamase gene,and the bla CTX-M gene had the highest carrying rate(85.71%,n=24).There were six combinations ofβ-lactamase gene profiles.Four quinolone resistance genes(AAC(6)-Ib-cr,oqxAB,qnrS and qnrC)were detected,and no amino acid mutation was found in GyrBand ParE.Fifteen isolates with both gyrA(Ser83Phe and Asp87Asn/Gly)and parC(Thr57Ser and Ser80Ile/Arg)mutations were resistant to ciprofloxacin at high levels(MIC≥16mL/L)regardless of the presence of quinolone resistance genes.This study showed that the prevalence of cephalosporin-resistant Salmonella strains in the pig industry chain in Henan Province was relatively low,and these Salmonellastrains had serious resistance to a variety of drugs,of which the phenotype of resistance toβ-lactams and fluoroquinolones was consistent with the genotype of resistance.