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Characterization of Shiga toxin-producing Escherichia coli isolated from healthy pigs in China
Authors:Qiong Meng  Xiangning Bai  Ailan Zhao  Ruiting Lan  Huamao Du  Tao Wang  Changyou Shi  Xuejiao Yuan  Xuemei Bai  Shaobo Ji  Dong Jin  Bo Yu  Yan Wang  Hui Sun  Kai Liu  Jianguo Xu  Yanwen Xiong
Institution:1. 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
2. Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China
3. School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
4. Biochemical and Molecular Biological Department, School of Biotechnology, Southwest University, Chongqing, China
5. Department of Microbiology, School of Basic Medical Sciences, Guiyang Medical University, Guiyang, China
6. Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, 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 stx 2 only, all of which were stx 2e subtype including 1 isolate being a new variant of stx 2e. 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, lpfA O113, lpfA O157/OI-154, lpfA O157/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.
Keywords:
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