Wang Lili, Nakamura Hiromi, Kage-Nakadai Eriko, Hara-Kudo Yukiko, Nishikawa Yoshikazu
Dalian University of Technology, School of Life Science and Biotechnology, Dalian 116024, China; Osaka City University, Graduate School of Human Life Science, Osaka 558-8585, Japan.
Department of Microbiology, Osaka City Institute of Public Health and Environmental Sciences, Osaka 543-0026, Japan.
Int J Food Microbiol. 2017 May 16;249:44-52. doi: 10.1016/j.ijfoodmicro.2017.03.003. Epub 2017 Mar 7.
Diarrheagenic E. coli (DEC) isolates were recovered from local retail markets and the Osaka Municipal Central Wholesale Market in Japan. Retail food samples were collected for analysis in Osaka Japan from 2005 to 2008 and consisted of 32 beef, 28 pork, 20 poultry, 136 fish, 66 fruits and vegetables and 51 ready-to-eat (RTE) food samples. A total of 82 DEC strains were recovered from 64 (19%) food samples with the highest prevalence in poultry (100%, 20/20), followed by pork (54%, 15/28), beef (28%, 9/32), fruits and vegetables (12%, 8/66), fish (6.6%, 9/136) and RTE foods (5.9%, 3/51). Most of the strains belonged to E. coli possessing the enteroaggregative E. coli (EAEC) heat-stable enterotoxin 1 (EAST1) gene (EAST1EC; n=62, P<0.0001) and enteropathogenic E. coli (EPEC; n=16, P<0.01), whereas only 1 strain belonged to Shiga toxin-producing E. coli (STEC), 1 to EAEC and 2 to enterotoxigenic E. coli (ETEC) strains. Of the 82 DEC isolates, 22 O and 13H serogroups were detected, including some specific serogroups (O91, O103, O115, O119, O126, and O157) which have been associated with human diarrheal infections. Phylogenetic group A and B1 were predominant among the DEC isolates. Antimicrobial resistance to tetracycline was most common (49%), followed by nalidixic acid (28%), ampicillin (24%), sulfamethoxazole/trimethoprim (20%), and cephalothin (18%). All isolates were susceptible to aztreonam. Of the resistant strains, 44% (22/50) demonstrated resistance to >3 antimicrobial agents. Isolates resistant to >5 antimicrobials were only found in the meat samples, while isolates from the fruits and vegetables as well as RTE foods showed resistance to only 1 or 2 antimicrobial agents. Sixty one percent of EAST1EC, 56% of EPEC and all of the EAEC and ETEC were resistant to at least 1 antimicrobial agent. Multiple-locus variable-number tandem repeat analysis (MLVA) was used in this study for genotyping of DEC. The 82 isolates collected for this study showed 77 distinct MLVA profiles located among 3 branches. The Simpson's Index of Diversity (D) was 99.9% at its highest. The high diversity of these food strains would suggest their originating from a variety of sources and environments. In conclusion, retail food samples in Japan were contaminated with DEC; EAST1EC, a putative DEC, were detected at high rates in poultry, pork and beef. Isolates resistant to >3 antimicrobials were found only in raw meat and fish. Food animals may act as the reservoir for multi-resistant bacteria. Due to the finding that nearly 1/3 of EAST1EC strains were resistant to >3 antimicrobials, additional surveillance for EAST1EC should be initiated.
致泻性大肠杆菌（DEC）分离株是从日本当地零售市场和大阪市中央批发市场采集的。2005年至2008年期间，在日本大阪采集零售食品样本进行分析，这些样本包括32份牛肉、28份猪肉、20份家禽肉、136份鱼肉、66份水果和蔬菜以及51份即食（RTE）食品样本。共从64份（19%）食品样本中分离出82株DEC菌株，在家禽肉中检出率最高（100%，20/20），其次是猪肉（54%，15/28）、牛肉（28%，9/32）、水果和蔬菜（12%，8/66）、鱼肉（6.6%，9/136）和即食食品（5.9%，3/51）。大多数菌株属于携带肠集聚性大肠杆菌（EAEC）热稳定肠毒素1（EAST1）基因的大肠杆菌（EAST1EC；n = 62，P < 0.0001）和肠致病性大肠杆菌（EPEC；n = 16，P < 0.01），而仅1株属于产志贺毒素大肠杆菌（STEC），1株属于EAEC，2株属于产肠毒素大肠杆菌（ETEC）菌株。在82株DEC分离株中，检测到22个O血清群和13个H血清群，包括一些与人类腹泻感染相关的特定血清群（O91、O103、O115、O119、O126和O157）。DEC分离株中以系统发育群A和B1为主。对四环素的耐药性最为常见（49%），其次是萘啶酸（28%）、氨苄西林（24%）、磺胺甲恶唑/甲氧苄啶（20%）和头孢噻吩（18%）。所有分离株对氨曲南敏感。在耐药菌株中，44%（22/50）对>3种抗菌药物耐药。仅在肉类样本中发现对>5种抗菌药物耐药的分离株，而水果和蔬菜以及即食食品中的分离株仅对1种或2种抗菌药物耐药。61%的EAST1EC、56%的EPEC以及所有的EAEC和ETEC对至少1种抗菌药物耐药。本研究采用多位点可变数目串联重复序列分析（MLVA）对DEC进行基因分型。本研究收集的82株分离株显示出77种不同的MLVA图谱，分布在3个分支中。辛普森多样性指数（D）最高为99.9%。这些食品菌株的高度多样性表明它们来源于多种来源和环境。总之，日本零售食品样本被DEC污染；推定的DEC即EAST1EC在家禽肉、猪肉和牛肉中检出率较高。仅在生肉和鱼肉中发现对>3种抗菌药物耐药的分离株。食用动物可能是多重耐药菌的储存宿主。鉴于近1/3的EAST1EC菌株对>3种抗菌药物耐药，应启动对EAST1EC的额外监测。
