华南地区食品中非O157致泻大肠杆菌分布特点及分型研究

Distribution and Molecular Typing(MLST) of Non-O157 Diarrheagenic Escherichia coli Isolated from Retail Foods in South China

为深入了解华南地区食品中非O157致泻大肠杆菌(DEC)的污染分布情况和特点,本研究随机采集了该地区12个城市的食品样品,参考GB/T 4789.36-2003方法进行检测,并利用多重PCR对DEC进行了分子鉴定。另外,分别采用MLST分型方法和药敏纸片法对DEC菌株的遗传特性和耐药性进行了分析。结果表明,1000份样品中有164份检出DEC,总污染率高达16.4%。肉类和水产品污染较严重。在五种DEC中,EPEC检出率最高(8.0%),其次为ETEC(6.2%),EIEC(3.4%)和STEC(0.4%)。样品中共分离到207株DEC。MLST分型产生了58种ST型,其中44个为已报道的ST型,14个为数据库中新的ST型。聚类分析表明这些菌株共有8个克隆复合物(CC),CC10为其中最大的一个。DEC菌株对四环素、复方新诺明、氨苄西林、头孢噻吩和氯霉素等具有高抗性。有关部门应加强非O157致泻大肠杆菌的监控,减少食源性疾病的发生。

To investigate the distribution and characteristics of non-O157 diarrheagenic Escherichia coli（DEC） contamination in retail foods in south China, food samples from 12 cities in this region were collected randomly and examined using the GB/T 4789.36-2003 method, and the molecular identification of DEC was conducted using multiplex polymerase chain reaction. In addition, multilocus sequence typing（MLST） and the paper disk method were used to analyze the genetic characteristics and drug resistance of DEC strains. The results showed that DEC was detected in 164 samples from 1000 food samples, with a total contamination rate of 16.4%. Severe contaminations were found in meat and aquatic products. Of the five DEC pathotypes tested, enteropathogenic E. coli showed the highest detection rate（8.0%）, followed by enterotoxigenic E. coli（6.2%）, enteroinvasive E. coli（3.4%）, and Shiga toxin-producing E. coli（0.4%）. A total of 207 DEC isolates was obtained, and the MLST results showed 58 different sequence types（STs）, including 44 reported STs and 14 novel STs. Cluster analysis indicated that eight clonal complexes（CCs） were obtained in these isolates, among which CC10 was the largest. The DEC isolates showed high resistance to tetracycline（72.5%）, trimethoprim-sulfamethoxazole（66.2%）, cephalothin（50.7%）, ampicillin（56.5%）, and chloramphenicol（48.3%）. The results of this study indicate that related agencies should strengthen the monitoring of non-O157 DEC to reduce the risk of outbreaks of foodborne diseases.