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

• Published in: Veterinary microbiology Vol. 124; no. 3; pp. 248 - 255
• Main Authors: Vo, An T.T., van Duijkeren, Engeline, Fluit, Ad C., Gaastra, Wim
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 06.10.2007; Elsevier Science
• Subjects: aminoglycosides; AmpC; Animals; Anti-Bacterial Agents - pharmacology; Antibiotic resistance; Bacteriology; beta-lactam antibiotics; beta-Lactamases - genetics; biochemical mechanisms; Biological and medical sciences; ceftiofur; Cephalosporin Resistance - genetics; cephalosporins; Cephalosporins - pharmacology; conjugation; Conjugation, Genetic; defense mechanisms; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; Drug Resistance, Multiple, Bacterial - genetics; Enterobacteriaceae; Escherichia coli; Escherichia coli - drug effects; Escherichia coli Infections - microbiology; Escherichia coli Infections - veterinary; Extended spectrum β-lactamases; Female; Fundamental and applied biological sciences. Psychology; gene transfer; Gene Transfer, Horizontal; genes; Horse; Horse Diseases - microbiology; Horses; integrons; Klebsiella Infections - microbiology; Klebsiella Infections - veterinary; Klebsiella pneumoniae; Klebsiella pneumoniae - drug effects; Male; microbial genetics; Microbial Sensitivity Tests - veterinary; Microbiology; Miscellaneous; molecular genetics; Molecular Sequence Data; multiple drug resistance; nucleotide sequences; Salmonella; strains; trimethoprim; AmpC; Extended spectrum β-lactamases; Horse; Antibiotic resistance; Enterobacteriaceae; Escherichia coli; Extended-spectrum β-lactamase; Resistance; Vertebrata; Antibiotic; Mammalia; Bacteria; Isolate; Perissodactyla; Veterinary; Ungulata; Klebsiella pneumoniae
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2007.04.027

The aim of the present study was to contribute to the knowledge on extended-spectrum β-lactamases (ESBL's), AmpC β-lactamases and integrons in Enterobacteriaceae isolated from horses, which is still limited. The susceptibility of 1581 clinical isolates from animals to ceftiofur was tested. Most of these isolates ( n = 1347) originated from horses. Seven ceftiofur-resistant equine isolates (four Escherichia coli and three Klebsiella pneumoniae) were identified and all seven were multidrug-resistant. These isolates were further studied for the presence of ESBL's, AmpC β-lactamases and class 1 integrons. The potential for the horizontal transfer of resistance genes among these clinical isolates was also studied. ESBL-type resistance genes were found in five isolates, AmpC-type genes in one isolates and integrons in six isolates. Nucleotide sequence analysis revealed that the isolates carried the bla CTX-M-1, bla CMY-2, bla TEM-1 and/or bla SHV-1 genes. This is the first report describing the in vitro conjugal transfer of the bla CTX-M-1 genes from a clinical E. coli isolate to Salmonella isolates. Gene cassettes encoding resistance to aminoglycosides ( aadA1, aad A2 and aadA5), and trimethoprim ( dfrA1, drfA12 and dfrA17) were found on the integrons present in the isolates. The cassette arrays of the dfrA17-aadA5 and dfrA1-aadA1 genes in the two integrons of a single E. coli isolate have not yet been described before. To our knowledge this is the first report on ESBL's and AmpC β-lactamases in equine E. coli and Klebsiella isolates.