1株携带mcr-1的食品动物源多药耐药奇异变形杆菌耐药性状分析

在对食品动物源性多药耐药菌的调查过程中,发现一株携带mcr-1的多药耐药奇异变形杆菌F160211,对其耐药表型及基因型进行进一步研究。通过扩增16S rRNA基因对该菌进行鉴定,用纸片扩散法初步鉴定了该菌的耐药谱,在此基础上测定多种药物对其最小抑菌浓度(minimum inhibitory concentration,MIC),用聚合酶链反应法扩增常见的耐药基因,最后分析携带mcr-1的质粒的复制类型。结果表明,该菌为奇异变形杆菌;纸片扩散法和肉汤稀释法测定耐药谱及MIC表明,该菌对青霉素类、第1代和第2代头孢菌素类、大环内酯类、氨基糖苷类、酰胺醇类、四环素类、磺胺类、利福霉素类和黏菌素类等耐药,对呋喃类、多肽类、喹诺酮类中介耐药,对第3代和第4代头孢菌素类、单环β-内酰胺类、碳青霉烯类、甘氨酰环素类敏感;常见耐药基因扩增表明,该菌携带bla_(CTX-M-1)、bla_(CTX-M-9)、bla_(TEM)、bla_(OXA-1)、mph(A)、qnr S和mcr-1等多种耐药基因;mcr-1基因位于与文献报道的pHNSHP45类似的IncI2型不相容性质粒上。本研究表明,mcr-1基因的宿主范围已由报道的大肠杆菌、沙门菌等进一步扩大至奇异变形杆菌,食品动物源性细菌耐药的形势非常严峻,对食品安全和公众健康都是严重的威胁。

Drug Resistance Analysis of a Multidrug-Resistant Proteus mirabilis Carrying the mcr-1 Gene Isolated from Food-Producing Animals

During the investigation of the prevalence of multidrug-resistant bacteria from food-producing animals, an mcr-1-carring multidrug-resistant strain of Proteus mirabilis was isolated and designated as F160211. Its drug-resistant profile and genotype were further investigated. The isolate was identified by 16S rRNA gene amplification and its drug-resistant profile was defined using a disk-based test and minimum inhibitory concentration (MIC) test. The drug-resistance genes were amplified by polymerase chain reaction (PCR). At last, the replication type of mcr-1-carring plasmid was analyzed. The results showed that the isolate F160211 was identified as P. mirabilis, and it was resistant to penicillin, first- and second-generation cephalosporins, macrolides, aminoglycosides, amphenicols, tetracyclines, sulfanilamides and rifamycins, and was intermediate to furans, polypeptide and quinolones, and was susceptible to third- and fourth-generation cephalosporins, monobactams, carbapenems, glycylcyclines and polymyxins. The drug-resistance genes that F160211 carried included blaCTX-M-1, blaCTX-M-9, blaTEM, blaOXA-1, mph(A), qnrS and mcr-1. The replicon PCR showed that mcr-1 was located in a IncI2 type plasmid, which was similar to pHNSHP45. These results showed that the mcr-1-harboring host bacteria have been extended from Escherichia coli and Salmonella to P. mirabilis and that the grim problem of multidrug-resistant bacteria from food-producing animals will pose a great threat to food safety and public health.