动物源性食品中抗生素残留、耐药细菌的分布及耐药基因的水平传播

Antibiotic residue,distribution of antibiotic resistant isolates and horizontal transfer of resistance genes in foods of animal origin

目的考查动物源性食品中抗生素的残留、耐药细菌的分布及抗生素对耐药基因水平转移的影响。方法利用盐析辅助液液萃取-高效液相色谱-串联质谱法对市售动物源性食品中18种抗生素的含量进行检测;对样品中的需氧菌进行分离鉴定,利用聚合酶链式反应(polymerase chain reaction,PCR)技术调查耐药基因的分布,以qnrS阳性菌株为供体菌、大肠杆菌J53为受体菌进行接合转移试验,调查抗生素胁迫对耐药基因水平传播的影响。结果50份动物源性食品中检出环丙沙星、恩诺沙星、土霉素、金霉素、磺胺嘧啶和磺胺二甲嘧啶。从50份样品共筛选出162株细菌,其中假单胞菌属、肠杆菌属、大肠杆菌和柠檬酸杆菌属所占比例较大,分别为17.28%、16.05%、14.81%和13.58%。药敏试验结果显示162株分离株对5种受试抗生素均表现出不同程度的耐药性,其中对四环素和磺胺甲基异恶唑的耐药率较高,分别为52.47%和51.23%。在3种喹诺酮类耐药基因中,qnrS检出率最高(15/162,9.26%);在3种磺胺类耐药基因中,sul1检出率最高(38/162,23.46%);在5种四环素类耐药基因中,tetM的检出率最高(28/162,17.28%)。以qnrS阳性菌株为供体菌、大肠杆菌J53为受体菌进行接合转移试验。在环丙沙星胁迫下,3株供体菌中耐药基因,qnrS的接合转移率均高于对照组。结论动物源性食品中喹诺酮类、磺胺类和四环素类抗生素均有不同程度的残留,耐药菌株和耐药基因在动物源性食品中分布较为广泛,亚抑菌浓度抗生素促进耐药基因的接合转移。

Objective To investigate antibiotic residue,distribution of antibiotic resistant isolates and horizontal transfer of antibiotic resistance genes in foods of animal origin.Methods Salting-out assisted liquid-liquid extraction and high performance liquid chromatography-tandem mass spectrometry were used to quantity 18 kinds of antibiotics in commercial foods of animal origin.Aerobic bacteria were identified from food samples and antibiotic genes were detected by polymerase chain reaction(PCR).Conjugative experiment was performed by using qnrS positive isolates as donors and Escherichia coli J53 as recipient to assess effects of antibiotic on horizontal transfer of antibiotic genes.Results Ciprofloxacin,enrofloxacin,oxytetracycline,chlortetracycline,sulfadiazine and sulfadimidine were detected in 50 food samples of animal origin.A total of 162 strains of bacteria were screened from 50 samples,among which,Pseudomons,Enterobacter,Escherichia coli and Citrobacter accounted for a lager proportion.Drug sensitivity testing results showed that 162 isolates exhibited varying degrees of resistance to 5 kinds of antibiotics tested in this study,with higher resistance to tetracycline and sulfamethoxazole.qnrS(15/162,9.26%)was the most prevalent among 3 kinds of quinolone resistance genes;sul1(38/162,23.46%)was the most prevalent among 3 kinds of sulfonamide resistance genes;and tetM(28/162,17.28%)was the most prevalent among 5 kinds of tetracycline resistance genes.When exposed to ciprofloxacin,the conjugation frequency of qnrS from 3 donors was higher than that in control group.Conclusions There are different degrees of residues of quinolones,sulfonamides and tetracycline in foods of animal origin.Antibiotic resistance isolates and resistance genes are widely distributed in foods of animal origin.Antibiotic at sub-inhibitory concentrations can facilitate the transferability of resistance genes.