Abstract
The emergence of antimicrobial resistance among Enterobacter spp., including resistance to extended-spectrum cephalosporins (ESC), is of great concern in both human and veterinary medicine. In this study, we investigated the prevalence of antimicrobial resistance among 60 isolates of Enterobacter spp., including E. cloacae (n = 44), E. aerogenes (n = 10), and E. asburiae (n = 6), from clinical specimens of dogs and cats from 15 prefectures in Japan. Furthermore, we characterized the resistance mechanisms harbored by these isolates, including extended-spectrum β-lactamases (ESBLs) and plasmid-mediated quinolone resistance (PMQR); and assessed the genetic relatedness of ESC-resistant Enterobacter spp. strains by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Antimicrobial susceptibility testing demonstrated the resistance rates to ampicillin (93.3%), amoxicillin-clavulanic acid (93.3%), cefmetazole (93.3%), chloramphenicol (46.7%), ciprofloxacin (43.3%), tetracycline (40.0%), ceftazidime (33.3%), cefotaxime (33.3%), trimethoprim/sulfamethoxazole (28.3%), gentamicin (23.3%), and meropenem (0%). Phenotypic testing detected ESBLs in 16 of 18 ESC-resistant E. cloacae isolates but not in the other species. The most frequent ESBL was CTX-M-15 (n = 8), followed by SHV-12 (n = 7), and CTX-M-3 (n = 1). As for AmpC β-lactamases, CMY-2 (n = 2) and DHA-1 (n = 2) were identified in ESC-resistant E. cloacae strains with or without ESBLs. All of the ESC-resistant E. cloacae strains also harbored one or two PMQRs, including qnrB (n = 15), aac(6’)-Ib-cr (n = 8), and qnrS (n = 2). Based on MLST and PFGE analysis, E. cloacae clones of ST591-SHV-12, ST171-CTX-M-15, and ST121-CTX-M-15 were detected in one or several hospitals. These results suggested intra- and inter-hospital dissemination of E. cloacae clones co-harboring ESBLs and PMQRs among companion animals. This is the first report on the large-scale monitoring of antimicrobial-resistant isolates of Enterobacter spp. from companion animals in Japan.
Highlights
Members of the genus Enterobacter, belonging to the Enterobacteriaceae, are Gram-negative bacilli that inhabit terrestrial and aquatic environments including water, sewage, and soil, as well as the intestinal tracts of mammals [1]
The aim of the present study was to investigate the prevalence of antimicrobial resistance, and provide molecular characterization of extended-spectrum cephalosporins (ESC) resistance and plasmid-mediated quinolone resistance (PMQR) among Enterobacter spp. isolates from clinical specimens taken from dogs and cats that visited veterinary hospitals throughout Japan
Antimicrobial resistance in Enterobacter spp. isolates from companion animals for epidemiological research by the Japanese government because this study focused on bacterial aspects
Summary
Members of the genus Enterobacter, belonging to the Enterobacteriaceae, are Gram-negative bacilli that inhabit terrestrial and aquatic environments including water, sewage, and soil, as well as the intestinal tracts of mammals [1]. Enterobacter cloacae is the most medically-important species in the genus and is responsible for nosocomial infections in humans [2]. In companion animals, this bacterial species is rarely associated with urinary tract infections, wound infections, pneumonia, intravenous catheter site infections, otitis externa, peritonitis, and dermatitis [3]. The emergence of antimicrobial resistance among Enterobacter spp. is of great concern worldwide in human medicine [1,2]. It increases the risk of antimicrobial treatment failure in humans and in companion animals. Understanding the prevalence of antimicrobial resistance among Enterobacter spp. isolates is important both from veterinary medicine and public health perspectives
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