Genotyping, Plasmid Analysis, and Antimicrobial Susceptibility of Salmonella enterica Serotype Enteritidis Isolates from Humans and Chickens in Central Taiwan

Chu, Chishih; Wong, Ding-Wei; Wang, Mei-Hui; Lin, Hsin-Hung; Chen, Yi-Sheng; Tien, Ni; Shih, Mu-Chin; Chen, Ter-Hsin; Chiu, Cheng-Hsun

doi:10.1016/S0929-6646(09)60403-4

« Previous Next »Journal of the Formosan Medical Association
Volume 108, Issue 10 , Pages 765-771, October 2009

Genotyping, Plasmid Analysis, and Antimicrobial Susceptibility of Salmonella enterica Serotype Enteritidis Isolates from Humans and Chickens in Central Taiwan

Chishih Chu
- Department of Microbiology and Immunology, National Chiayi University, Chiayi, Taiwan
- Chishih Chu and Ding-Wei Wong contributed equally to this work.
Ding-Wei Wong
- Department of General Surgery, Armed Forces Taichung General Hospital, Taichung, Taiwan
- Chishih Chu and Ding-Wei Wong contributed equally to this work.
Mei-Hui Wang
- Department of Microbiology and Immunology, National Chiayi University, Chiayi, Taiwan
Hsin-Hung Lin
- Department of Microbiology and Immunology, National Chiayi University, Chiayi, Taiwan
Yi-Sheng Chen
- Department of Microbiology and Immunology, National Chiayi University, Chiayi, Taiwan
Ni Tien
- Department of Laboratory Medicine, China Medical University Hospital, Taichung, Taiwan
Mu-Chin Shih
- Department of Laboratory Medicine, China Medical University Hospital, Taichung, Taiwan
Ter-Hsin Chen
- Graduate Institute of Veterinary Public Health, National Chung Hsin University, Taichung, Taiwan
Cheng-Hsun Chiu
- Department of Pediatrics, Chang Gung Children's Hospital, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan
- Correspondence to: Dr Cheng-Hsun Chiu, Department of Pediatrics, Chang Gung Children's Hospital, 5 Fu-Hsin Street, Kweishan, Taoyuan 333, Taiwan

Received 17 September 2008; received in revised form 31 March 2009; accepted 2 April 2009.

Background/Purpose

Salmonella enterica serotype Enteritidis (SE) is the most frequent etiological agent of human salmonellosis. The molecular epidemiology and antimicrobial susceptibility of human and chicken isolates of SE were examined.

Methods

A total of 27 human and 40 chicken isolates of SE were collected in 2005–2006. We examined these isolates by antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE), and plasmid analysis.

Results

Most isolates were susceptible to the seven antibiotics tested, except chicken isolates in 2005, which showed 70% resistance to streptomycin and 75% to tetracycline. There were six plasmid profiles identified among these isolates. Almost all isolates (97%) harbored the 60-kb serotype-specific virulence plasmid. PFGE using Xba I digestion separated human isolates into eight subtypes (1a–1h) and chicken isolates into four subtypes (1a–1c and 1g). In 2005, 1a and 1c were predominant for human isolates and 1a for chicken isolates. However, in 2006, 1a and 1c remained predominant for human isolates and 1b and 1c for chicken isolates. Most 1b and 1c isolates belonged to plasmid type 2 or 4. Correlation between plasmid patterns and PFGE subtypes was obtained between a 36-kb plasmid and 1b and between another 3.6-kb plasmid and 1a.

Conclusion

Plasmid profiling and PFGE were efficient for discriminating SE isolates from different sources. Our data support the notion that SE is transmitted from chickens to humans, presumably through the food chain, but it appears that chickens are not the sole reservoir for human infection with SE in Taiwan. SE remained susceptible to most antimicrobial agents.

Key Words: antibacterial drug resistance , bacterial typing techniques , genotype , plasmids , Salmonella enterica serotype Enteritidis