Epidemiologic relationship between fluoroquinolone-resistant Salmonella enterica serovar choleraesuis strains isolated from humans and pigs in Taiwan (1997 to 2002)

Chao Chin Chang, Yi Hsuan Lin, Chao Fu Chang, Kuang Sheng Yeh, Cheng Hsun Chiu, Chishih Chu, Maw Sheng Chien, Yuan Man Hsu, Li Shu Tsai, Chien Shun Chiou

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The emergence of ciprofloxacin-resistant Salmonella enterica serovar Choleraesuis in recent years has become an important public health issue in Taiwan. The resistant strains that cause human infections are considered to be from pigs. In this study, we characterized 157 swine and 42 human Salmonella serovar Choleraesuis isolates by pulsed-field gel electrophoresis (PFGE) and drug susceptibility testing to investigate the epidemiologic relationship among the isolates. By PFGE analyses, two major clusters (clusters GA and GB) were identified. Isolates in cluster GA were of both human and swine origins, while those in cluster GB were from pigs only. Among the various genotypes identified, genotype gt-la was the most prevalent, which was found in 71% (30 of 42) and 48% (76 of 157) of human and swine isolates, respectively. The susceptibility tests for the 106 gt-1a isolates identified 44 susceptibility profiles and showed that 73% of human isolates and 34% of swine isolates were resistant to three fluoroquinolones (ciprofloxacin, enrofloxacin, and norfloxacin). Our findings indicate that a clonal group of Salmonella serovar Choleraesuis may have been circulating in human and swine populations in Taiwan for years and that the fluoroquinolone-resistant Salmonella serovar Choleraesuis strains most likely evolved from a gt-1a clone that emerged in 2000 and that then caused widespread infections in humans and pigs. Nevertheless, it is still debatable whether those Salmonella infections in humans are caused by isolates derived from pigs, on the basis of the higher fluoroquinolone and other antimicrobial resistance percentages in human isolates than in pig isolates.

Original languageEnglish
Pages (from-to)2798-2804
Number of pages7
JournalJournal of Clinical Microbiology
Issue number6
Publication statusPublished - Jun 2005


ASJC Scopus subject areas

  • Microbiology (medical)
  • Microbiology

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