title: Characterization of Shiga toxin-producing Escherichia coli isolated from healthy pigs in China.
abstract: BACKGROUND
  Shiga toxin-producing Escherichia coli (STEC) is recognized as an important human diarrheal pathogen. Swine plays an important role as a carrier of this pathogen. In this study we determined the prevalence and characteristics of STEC from healthy swine collected between May 2011 and August 2012 from 3 cities/provinces in China.
  
  
  RESULTS
  A total of 1003 samples, including 326 fecal, 351 small intestinal contents and 326 colon contents samples, was analyzed. Two hundred and fifty five samples were stx-positive by PCR and 93 STEC isolates were recovered from 62 stx-positive samples. Twelve O serogroups and 19 O:H serotypes including 6 serotypes (O100:H20/[H20], O143:H38/[H38], O87:H10, O172:H30/[H30], O159:H16, O9:H30/[H30]) rarely found in swine and ruminants were identified. All 93 STEC isolates harbored stx2 only, all of which were stx2e subtype including 1 isolate being a new variant of stx2e. 53.76%, 15.05% and 2.15% STEC isolates carried astA, hlyA and ehxA respectively. Four STEC isolates harbored the high-pathogenicity island. Of the 15 adherence-associated genes tested, 13 (eae, efa1, iha, lpfAO113, lpfAO157/OI-154, lpfAO157/OI-141, toxB, saa, F4, F5, F6, F17 or F41) were all absent while 2 (paa and F18) were present in 7 and 4 STEC isolates respectively. The majority of the isolates were resistant to tetracycline (79.57%), nalidixic acid (78.49%), trimethoprim-sulfamethoxazole (73.12%) and kanamycin (55.91%). The STEC isolates were divided into 63 pulsed-field gel electrophoresis patterns and 21 sequence types (STs). Isolates of the same STs generally showed the same or similar drug resistance patterns. A higher proportion of STEC isolates from Chongqing showed multidrug resistance with one ST (ST3628) resistant to 14 antimicrobials.
  
  
  CONCLUSIONS
  Our results indicate that swine is a significant reservoir of STEC strains in China. Based on comparison by serotypes and sequence types with human strains and presence of virulence genes, the swine STEC may have a low potential to cause human disease.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Meng
authors.forename: Xiangning
authors.initials: X
authors.lastname: Bai
authors.forename: Ailan
authors.initials: A
authors.lastname: Zhao
authors.forename: Ruiting
authors.initials: R
authors.lastname: Lan
authors.forename: Huamao
authors.initials: H
authors.lastname: Du
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.forename: Changyou
authors.initials: C
authors.lastname: Shi
authors.forename: Xuejiao
authors.initials: X
authors.lastname: Yuan
authors.forename: Xuemei
authors.initials: X
authors.lastname: Bai
authors.forename: Shaobo
authors.initials: S
authors.lastname: Ji
authors.forename: Dong
authors.initials: D
authors.lastname: Jin
authors.forename: Bo
authors.initials: B
authors.lastname: Yu
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.forename: Kai
authors.initials: K
authors.lastname: Liu
authors.forename: Jianguo
authors.initials: J
authors.lastname: Xu
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China. xiongyanwen@icdc.cn.
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Xiong
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D002681:China; D016000:Cluster Analysis; D003106:Colon / Q000382:microbiology; D004197:Disease Reservoirs; D016521:Electrophoresis, Gel, Pulsed-Field; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics; D005243:Feces / Q000382:microbiology; D005838:Genotype; D007421:Intestine, Small / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D016133:Polymerase Chain Reaction; D015995:Prevalence; D012703:Serotyping; D022621:Shiga Toxin / Q000145:classification / Q000235:genetics; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D013552:Swine; D037521:Virulence Factors / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D037521:Virulence Factors; D022621:Shiga Toxin