广东省某生猪屠宰场tet(X4)和bla_(NDM)阳性菌的流行特征

Epidemiological Characteristic of tet(X4)and bla_(NDM) Positive Strains in a Swine Slaughterhouse in Guangdong Province

为了探究广东省某生猪屠宰场中替加环素耐药基因tet(X4)和碳青霉烯耐药基因bla_(NDM)阳性菌的流行特征,本试验从广东省某生猪屠宰场采集94份不同来源样品(55份猪粪便、20份屠宰场环境和19份猪胴体),使用含替加环素和美罗培南的麦康凯琼脂培养基筛选替加环素和美罗培南不敏感菌株;采用PCR方法检测tet(X4)和bla_(NDM)基因阳性菌,并对阳性菌进行菌种鉴定;采用微量肉汤稀释法和琼脂稀释法测定阳性菌的药物敏感性。结果显示,所有样品的tet(X4)和bla_(NDM)阳性菌检出率分别为93.62%(88/94)和51.06%(48/94),其中tet(X4)基因阳性菌的检出率在猪粪便样品中最高(98.18%,54/55),其次是胴体样品(89.47%,17/19)和环境样品(85.00%,17/20);bla_(NDM)因阳性菌的检出率在环境样品中最高(80.00%,16/20),其次是猪粪便样品(47.27%,26/55)和胴体样品(31.58%,6/19)。2种耐药基因的主要携带菌种均为大肠杆菌,分别占比95.65%(88/92)和74.07%(40/54),另外也检测到tet(X4)阳性的弗格森埃希菌、阴沟肠杆菌和摩氏摩根菌,bla_(NDM)阳性的肺炎克雷伯菌、雷氏普罗威登斯菌和瓜里科州假单胞菌等。药敏试验结果显示,tet(X4)和bla_(NDM)阳性大肠杆菌均为多重耐药菌,其中tet(X4)阳性菌对四环素和氟苯尼考的耐药率为100%;bla_(NDM)阳性菌对头孢噻肟和头孢他啶的耐药率为100%;2种基因阳性菌均对黏菌素较为敏感。结果表明,该屠宰场tet(X4)和bla_(NDM)阳性菌污染严重,主要菌种为大肠杆菌。屠宰场tet(X4)和bla_(NDM)阳性菌的污染对食品安全和公共卫生构成威胁,提示应加强对生猪屠宰场中耐药菌污染情况调查和长期监测。

To explore the epidemiological characteristics of tet(X4)and bla_(NDM) positive strains in a swine slaughterhouse in Guangdong Province,94 samples from various sources(55 pig feces,20 slaughterhouse environments,and 19 pig carcasses)were collected.MacConkey agar supplemented with tigecycline and meropenem was used to screen for tigecycline-and meropenem-resistant strains.PCR was employed to detect tet(X4)and bla_(NDM) positive genes,and positive strains were identified.The drug sensitivity of positive strains was determined by the microdilution broth method and agar dilution method.The results showed that the detection rates of tet(X4)and bla_(NDM) positive strains in all samples were 93.62%(88/94)and 51.06%(48/94),respectively.Among them,the detection rate of tet(X4)positive strains was highest in pig feces samples(98.18%,54/55),followed by carcass samples(89.47%,17/19),and environmental samples(85.00%,17/20).The detection rate of bla_(NDM) positive strains was highest in environmental samples(80.00%,16/20),followed by pig feces samples(47.27%,26/55),and carcass samples(31.58%,6/19).The main carriers of the two resistant genes were Escherichia coli,accounting for 95.65%(88/92)and 74.07%(40/54),respectively.Additionally,tet(X4)positive Escherichia fergusonii,Enterobacter cloacae and Morganella morganii,as well as bla_(NDM) positive Klebsiella pneumoniae,Providencia rettgeri and Pseudomonas guariconensis were also detected.The drug sensitivity test results showed that tet(X4)and bla_(NDM) positive Escherichia coli were multidrug resistant,with a resistance rate of 100%to tetracycline and florfenicol for tet(X4)positive strains,and 100%to cefotaxime and ceftazidime for bla_(NDM) positive strains;both types of positive strains were relatively sensitive to colistin.These results indicate that tet(X4)and bla_(NDM) positive strains are severely contaminated in the slaughterhouse,with Escherichia coli being the main species.The contamination of tet(X4)and bla_(NDM) positive strains in the slaughterhouse poses a threat to food safety and public health,highlighting the need to strengthen investigation and long-term monitoring of antibiotic-resistant bacteria contamination in swine slaughterhouses.