乳品生产链金黄色葡萄球菌的污染、耐药性分析及β-内酰胺类药物耐药基因的检测

Analysis on Contamination and Drug Resistance and Detection of Beta-lactam Drug Resistance Genes in Staphylococcus aureus Isolated from the Dairy Production Chain

为分析乳品生产链中金黄色葡萄球菌(Sa)的污染及耐药情况,从部分乳品生产企业采集乳样(生鲜牛乳、生产车间半成品牛乳、成品牛乳)523份,按照GB 4789.10-2010及PCR方法分离鉴定Sa菌株1;采用微量肉汤稀释法,测定Sa分离株对12种抗生素的药敏性,并利用多重PCR方法分析Sa对β-内酰胺类药物耐药性的产生与其耐药相关基因(mecA、blaZ)的关联性。结果显示,乳样Sa总分离率为24.9%(129株),其中生鲜牛乳、中间半成品牛乳及成品牛乳Sa污染率分别为37.5%、7.1%和0.0%;受试Sa分离株对青霉素的耐药率(97.7%)最高,其它依次是氨苄西林(95.4%)、甲氧苄啶/磺胺甲噁唑(61.9%)、阿莫西林/克拉维酸(61.7%)、红霉素(39.7%)、四环素(36.6%)、盐酸林可霉素(35.2%);所有菌株均对苯唑西林、头孢噻呋、氟苯尼考敏感;多重耐药Sa分离率为69.8%,主要对青霉素类、磺胺类、大环类脂类、林可胺类及四环素类表现出多重耐药;多重PCR检测结果显示,129株测试Sa的nuc、blaZ、mecA阳性率分别为100.0%、60.5%及0.0%;不同生产环节乳源Sa携带blaZ基因与其对β-内酰胺类药物的耐药表型有一定的对应关系。结果表明,乳品生产链Sa污染及耐药现状已不容乐观,应引起重视,避免食源性疾病的发生。

To analyze the contamination situation and drug resistance of Staphylococcus aureus （Sa） in the dairy production chain, 523 samples of dairy food （raw milk, semi-finished milk, milk products） were collected. With ref- erence to GB 4789.10 -2010 and PCR, the isolation and identification of Sa were carried out using broth dilution method to determine the antimicrobial susceptibility to 12 antibiotics of Sa isolates. Multiplex PCR was used to analyze the relationship between the resistance to beta-lactams and the antimicrobial resistance genes （mecA, blaZ）. The Re- suits indicated that the total detectable rate of Sa was 24.9% （129 samples） , in which, the positive rate in raw milk, semi-finished milk and milk products were 37.5% , 7.1% and 0.0% respectively. All the isolates were mostly resist- ant to penicillin （ 97.7% ） , followed by resistance to ampicillin （ 95.4% ） , trlmethoprim/sulfamethoxazole （61.9%） , amoxicillin/clavulanic acid （61.7%） , erythromycin （39.7%） , tetracycline （36.6%） , clindamycin （35.2%）. All strains were susceptible to oxacillin, ceftiofur, florfenicol. 69.8% of the isolates were multi-drug resistant, the whole test strains were multi-drug resistant mainly to penicillins, sulfonamides, macrocyclie lipids, lincosamldes and tetracyclines. The positive rates for detection of nuc and blaZ genes by PCR were 100.0% , 60.5% and 0.0% respectively. There were a lot Correspondence between the resistance to beta-lactams and the detection rate of the resistance gene （blaZ） about Sa from different segments of dairy production chain. The contamination and drug resistance of Sa isolates recovered from dairy production chain were not optimistic, so we must take it seriously and avoid the occurrence of food-borne illness