Trends in antimicrobial resistance, phage types and integrons among Salmonella serotypes from pigs, 1997-2000

Wondwossen A. Gebreyes, Siddhartha Thakur, Peter R. Davies, Julie A. Funk, Craig Altier

Research output: Contribution to journalArticlepeer-review

88 Scopus citations


Objectives: The objectives of this study were to determine antimicrobial resistance and to identify phage types and class 1 integrons among non-typhoidal Salmonella isolates from 24 pig farms in North Carolina collected between 1997 and 2000. Methods: A total of 1314 isolates of 30 serotypes from pig faecal samples were collected and analysed over a 3 year period. The isolates were characterized using antimicrobial susceptibility testing, phage typing, PCR and DNA sequencing for class 1 integrons. Results: A high frequency of resistance to antimicrobial agents including tetracycline (85%), ampicillin (47%), co-amoxiclav (23%) and chloramphenicol (21%) was detected. Two multidrug resistance patterns were common in Typhimurium (including variant Copenhagen): isolates with co-amoxiclav, ampicillin, chloramphenicol, streptomycin, sulfamethoxazole and tetracycline (R-type AxACSSuT) [36%] and isolates with ampicillin, kanamycin, streptomycin, sulfamethoxazole and tetracycline (R-type AKSSuT) [45%] resistance patterns. Definitive Type 104 (DT104) was the most common (34%) among eight phage types identified. AKSSuT was found among non-DT104 phage types, particularly DT21 and DT193. Class 1 integrons were detected among various serotypes including Typhimurium, Derby, Muenchen, Worthington, Bere and Muenster. aadA was the most common resistance gene insert, and the oxa30 β-lactamase resistance gene was also identified among serovar Muenchen. Conclusions: In this study, two most important multidrug resistance patterns (AxACSSuT and AKSSuT) and phage types of public health significance (DT104 and DT193) constituted two-thirds of the serotype Typhimurium isolates. The findings imply that pigs raised in the commercial production system may pose a risk in serving as reservoirs of resistant Salmonella.

Original languageEnglish (US)
Pages (from-to)997-1003
Number of pages7
JournalJournal of Antimicrobial Chemotherapy
Issue number6
StatePublished - Jun 2004
Externally publishedYes


  • Antibiotic resistance
  • Food safety
  • Salmonellae
  • Swine

ASJC Scopus subject areas

  • Pharmacology
  • Microbiology (medical)
  • Infectious Diseases
  • Pharmacology (medical)


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