重庆地区畜禽源大肠杆菌耐药性变化分析

Changes in drug resistance of poultry and livestock sourced Escherichia coli in Chongqing

  • 摘要: 【目的】 对比重庆地区近10年来畜禽源大肠杆菌对常用抗菌药物的耐药率及部分可水平转移耐药基因阳性率的变化趋势,为该地区大肠杆菌耐药性的科学控制提供参考依据。【方法】 从重庆市12个区县的13个养殖场采集畜禽粪便样本,经细菌分离纯化后共获得157株大肠杆菌(2007—2008年76株,2020年81株),通过体外抑菌试验检测受试大肠杆菌对18种抗菌药物的敏感性,采用PCR检测39株多重耐药大肠杆菌中的17种可水平转移耐药基因,利用MLST分型和系统进化分群探析其分子进化关系,并根据耐药谱对9株多重耐药大肠杆菌进行全基因组测序。【结果】 重庆地区畜禽源大肠杆菌的多重耐药率由2007—2008年的96.05%降至2020年的75.31%,对四环素类(土霉素和米诺环素)、酰胺醇类(氟苯尼考)、氟喹诺酮类(恩诺沙星和环丙沙星)、氨基糖苷类(链霉素、庆大霉素和阿米卡星)的耐药率由13.16%~85.53%降至0~45.68%,耐药谱以五重~六重为主转变为以二重~四重为主。相对于2007—2008年分离菌株,2020年分离菌株对磺胺类(sul1)、β-内酰胺类(blaTEM)、氨基糖苷类[aadA1aph(3')-Ia]和多肽类(mcr-1)耐药基因的检出率呈下降趋势,但对酰胺醇类(floR)和喹诺酮类(qnrS)耐药基因的检出率呈上升趋势。选取的39株受试大肠杆菌存在29种ST型,其中3种为新发现的ST型,分别是ST12677、ST12678和ST12679;系统进化分群分布相似,可分为A群、B1群和D群。受试大肠杆菌检出可水平转移耐药基因的个数和种类较丰富,其中,2007—2008年分离菌株检出10~14个(4~7类)可水平转移耐药基因,2020年分离菌株检出9~18个(6~10类)可水平转移耐药基因。【结论】 重庆地区畜禽源大肠杆菌对部分抗菌药物的耐药性明显下降,多重耐药现象得到一定程度的缓解,但部分菌株仍携带大量可水平转移耐药基因,因此其水平传播方式及控制措施还有待进一步探究,应根据耐药性变化趋势建立适宜的替抗方案,以逐步改善多重耐药现状及维护公共卫生安全。

     

    Abstract: 【Objective】 To compare the changes in antimicrobial resistance rates and the prevalence of horizontally transferable drug resistance genes in Escherichia coli from livestock and poultry in Chongqing over the past decade,providing scientific basis for controlling E. coli antimicrobial resistance in this region. 【Method】 Fecal samples were collected from livestock and poultry on 13 farms across 12 districts in Chongqing. A total of 157 E. coli strains(76 from 2007-2008 and 81 from 2020)were obtained after bacterial isolation and purification. Antimicrobial susceptibility to 18 antibiotics was evaluated through in vitro bacteriostatic tests. PCR was used to detect 17 horizontally transferable drug resistance genes in 39 multi-drug resistant E. coli strains. Molecular evolution relationships were analyzed using multilocus sequence typing(MLST)and phylogenetic clustering. Nine multidrug resistant E. coli strains were selected for whole-genome sequencing based on their resistance spectrum. 【Result】 The multi-drug resistance rate of livestock and poultry E. coli in Chongqing decreased from 96.05% during 2007-2008 to 75.31% in 2020. Resistance rates to tetracyclines(oxytetracycline,minocycline),amphenicols(florfenicol),fluoroquinolones(enrofloxacin,ciprofloxacin),and aminoglycosides (streptomycin,gentamicin,amikacin)declined from 13.16%-85.53% to 0-45.68%. The resistance spectrum shifted from predominantly five- to six-drug resistance to two- to four-drug resistance. Compared to 2007-2008 isolates,2020 isolates showed decreased detection rates of resistance genes for sulfonamides(sul1),β -lactams(blaTEM),aminoglycosides [aadA1 and aph(3')-Ia and polymyxins(mcr-1),but increased detection rates for genes related to amphenicols(floR) and quinolones(qnrS). Among the 39 tested strains,29 sequence types(STs)were identified,including 3 novel STs: ST12677,ST12678,and ST12679. Phylogenetic clustering revealed similar distributions,with all isolates grouped into A,B1,and D clusters. Horizontally transferable drug resistance genes were abundant in quantity and types,with isolates from 2007-2008 carrying 10-14 genes(4-7 types)and those from 2020 carrying 9-18 genes(6-10 types). 【Conclusion】 While resistance of E. coli strains from livestock and poultry to certain antibiotics has greatly declined in Chongqing,and multi-drug resistance has been alleviated to some extents,some strains still carry a substantial number of transferable drug resistance genes. This highlights the importance of further investigation into horizontal transmission mechanisms and control strategies. Developing suitable alternative antimicrobial programs based on resistance trends may help mitigate multidrug resistance and safeguard public health.

     

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