Characteristics of extended-spectrum cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae isolates from horses.

This study researches on a particular type of antibiotic resistance in bacteria found in horses, with focus on extended-spectrum beta-lactamases (ESBL’s), AmpC beta-lactamases and integrins in Enterobacteriaceae. Seven resistant pathogens identified from these tests possess multiple antibiotic resistances and carry genetic resistance that could be potentially transferable.

Objective and Methodology of the Research

• The goal of the investigation was to enhance understanding of ESBL’s, AmpC beta-lactamases and class 1 integrons within Enterobacteriaceae sourced from horses.
• The researchers scrutinized 1581 clinical isolates obtained from animals to confirm their susceptibility to the antibiotic ceftiofur. Out of these, the majority (1347) came from horses.
• They discovered seven equine isolates resistant to ceftiofur (four Escherichia coli and three Klebsiella pneumoniae) which were also multi-drug resistant. These seven types were further examined for ESBL’s, AmpC beta-lactamases, class 1 integrons and their potential for horizontal gene transfer.

Findings of the Study

• Five isolates had ESBL-type resistant genes, one had AmpC-type, and six carried class 1 integrons. Detailed analysis revealed these isolates bore the resistance genes bla(CTX-M-1), bla(CMY-2), bla(TEM-1), and/or bla(SHV-1).
• This research revealed the first identified incident of in vitro horizontal transfer of bla(CTX-M-1) resistance genes from E. coli clinical isolates to Salmonella isolates.
• Gene cassettes that code resistance to aminoglycosides (aadA1, aadA2, aadA5) and trimethoprim (dfrA1, drfA12, dfrA17) were found nested within the integrons of the isolates.
• Two unique cassette arrangements, dfrA17-aadA5 and dfrA1-aadA1, lodged within the integrons of a singular E. coli isolate, were recounted for the first time.

Significance of the Research

• This was the first known report on extended-spectrum beta-lactamases (ESBL’s) and AmpC beta-lactamases in equine E. coli and Klebsiella pneumoniae isolates.
• The research highlights the potential threat of multiresistant bacteria in animals, and the potential for these pathogens to transfer resistance to other bacteria.