Antimicrobial and Biocide Resistance among Canine and Feline Enterococcus faecalis , Enterococcus faecium , Escherichia coli , Pseudomonas aeruginosa , and Acinetobacter baumannii Isolates from Diagnostic Submissions

A total of 215 isolates from infections of dogs and cats, including 49 , 37 , 59 , 56 , and 14 , were investigated for their susceptibility to 27 (Gram-positive bacteria) or 20 (Gram-negative bacteria) antimicrobial agents/combinations of antimicrobial agents by broth microdilution according to the recommendations of the Clinical and Laboratory Standards Institute. Moreover, all isolates were analysed for their susceptibility to the biocides benzalkonium chloride, chlorhexidine, polyhexanide, and octenidine by a recently published broth microdilution biocide susceptibility testing method. While the isolates did not show expanded resistances, considerable numbers of the isolates were resistant to penicillins, macrolides, tetracyclines, and fluoroquinolones. Even a single vancomycin-resistant isolate that carried the gene cluster was detected. Expanded multiresistance phenotypes were also detected among the isolates, including a single carbapenem-resistant, -positive isolate. In addition, multiresistant isolates were detected. The minimal inhibitory concentrations of the biocides showed unimodal distributions but differed with respect to the biocide and the bacterial species investigated. Although there were no indications of a development of biocide resistance, some isolates exhibited benzalkonium MICs higher than the highest test concentration.