猪源大肠杆菌的耐药性与锌抗性相关性的研究

Study on correlation between antimicrobial resistance and zinc resistance of porcine Escherichia coli

为了解猪源大肠杆菌的耐药性与大肠杆菌对重金属锌抗性的现状,探究耐药基因与锌抗性基因的流行特征及二者之间的相关性,本研究采集普通猪场(A猪场)、从未使用过抗生素生长促进剂(AGP)的猪场(B猪场)以及未使用氧化锌和AGP的猪场(C猪场)共335份粪便样品,分离大肠杆菌,采用微量肉汤稀释法测定大肠杆菌分离株对10种抗菌药物和硫酸锌的敏感性,并采用PCR检测分离菌的耐药基因和锌抗性基因。结果显示,在335份采集样品中共分离出288株大肠杆菌。药敏试验结果显示,猪源大肠杆菌对四环素耐药的菌株数占比最高达95.83%(276/288),对呋喃妥因和多粘菌素B的耐药菌株占比最低,分别占7.99%(23/288)和12.15%(35/288),其中A猪场大肠杆菌分离株对10种抗生素的耐药占比均高于B猪场。抗性基因检测结果显示,锌抗性基因zitB检出率最高达99.65%,还检出了较高水平的锌抗性基因czcB、czcA及zntA;β-内酰胺类耐药基因ampC检出率为98.26%,氯霉素类耐药基因cat1检出率仅为4.86%。其中A猪场与B猪场的4种锌抗性基因检出率均高于C猪场。相关性分析结果显示,锌抗性基因zntA、czcA、czcB对四环素类耐药基因tetA呈显著正相关(P<0.05),与多粘菌素类耐药基因mcr-1呈极显著负相关(P<0.01)。其中锌抗性基因zntA、czcA与耐药基因cmlA、qnrs、nfsA和nfsB均为极显著的正相关(P<0.01)。上述结果首次表明重金属锌可能诱导了动物肠道大肠杆菌的耐药性以及多重耐药表型,并且抗生素可能会影响猪大肠杆菌的锌抗性。本研究为后期养殖场抗生素及氧化锌的合理使用提供重要参考。

In order to understand the antibiotic resistance of porcine E.coli and the status quo of E.coli resistance to heavy metal zinc,and explore the epidemic characteristics and correlation between resistance genes and zinc resistance genes.In this study,a total of 335 fecal samples were collected from normal pigs farm(A),pigs farms that had never used antibiotic growth promoters(AGP)(B),and pigs farms that had not used zinc oxide and AGP(C).E.coli was isolated from feces.The sensitivity of E.coli isolates to 10 kinds of antibiotics and zinc sulfate was determined by microbroth dilution method,and the antibiotic resistance genes and zinc resistance genes were detected by PCR.The results showed thata total of 288 E.coli strains were isolated from 335 samples collected.The results of antimicrobial sensitivity showed that the antibiotic with the highest proportion of antibiotic-resistant strains was tetracycline,accounting for 95.83%(276/288),and the proportion of resistance to NIT and PB was the lowest,they accounted for 7.99%(23/288)and 12.15%(35/288),respectively.The proportion of resistance of E.coli isolates from farm A to 10 kinds of antibiotics was higher than that from pig farm B.The detection rate of zinc resistance gene zitB was 99.65%,β-lactam resistance gene ampC was 98.26%,and chloramphenicol resistance gene cat1 was only 4.86%.The detection rates of four zinc resistance genes in farms A and B were higher than those in farms C.The results of correlation analysis showed that zinc resistance genes zntA,czcA and czcB showed significantly positive correlation to tetA(P<0.05),and significantly negative correlation to mcr-1(P<0.01).The zinc resistance genes zntA and czcA were positively correlated with cmlA,qnrs,nfsA and nfsB(P<0.01).The above results suggest that heavy metal zinc may induce drug resistance and multiple resistance phenotypes of enteric E.coli in animals,and antibiotics may affect zinc resistance of E.coli in pig feces.This study provides an important reference for the use of antibiotics and zinc oxide in later clinical aquaculture.