Multidrug-Resistant ESBL/AmpC-Producing Klebsiella pneumoniae Isolated from Healthy Thoroughbred Racehorses in Japan

Abstract

Extended-spectrum β-lactamase (ESBL)- and AmpC β-lactamase (AmpC)-producing Klebsiella spp. have become a major health problem, leading to treatment failure in humans and animals. This study aimed to evaluate the presence of ESBL/AmpC-producing Klebsiella spp. isolated from racehorses in Japan. Feces samples from 212 healthy Thoroughbred racehorses were collected from the Japan Racing Association Training Centers between March 2017 and August 2018. ESBL/AmpC-producing Klebsiella spp. were isolated using selective medium containing 1 µg/mL cefotaxime. All isolates were subjected to bacterial species identification (MALDI-TOF MS), antimicrobial susceptibility test (disk diffusion test), characterization of resistance genes (PCR), conjugation assay, and genetic relatedness (multilocus sequence typing/MLST). Twelve ESBL/AmpC-producing Klebsiella pneumoniae (ESBL/AmpC-KP) were isolated from 3.3% of horse samples. Antimicrobial resistance profiling for 17 antimicrobials showed all ESBL/AmpC-KP were multidrug-resistant (MDR). Only 1 isolate was confirmed as an ESBL producer (blaCTX-M-2-positive), whereas the other 11 isolates were plasmid-mediated AmpC (pAmpC) producers (blaCMY positive). On the basis of MLST analysis, the ESBL-KP isolate was identified as sequence type (ST)-133 and four different STs among AmpC-KP isolates, ST-145, ST-4830, ST-4831, and ST-4832, were found to share six of the seven loci constituting a single-locus variant. This is the first study to show K. pneumoniae carrying MDR pAmpC isolated from a racehorse.

Antimicrobial resistance profiles and phylogenetic groups of <i>Escherichia coli</i> isolated from healthy Thoroughbred racehorses in Japan

“…Intrinsically, E. coli is resistant to penicillin, and acquired resistance to β-lactams is mostly mediated by the production of β-lactamases such as TEM-1, TEM-2, SHV-1, and AmpC β-lactamase [ 18 ]. Resistance due to ESBL-producing E. coli and Klebsiella pneumoniae has been reported in TB racehorses in our previous studies [ 26 , 27 ]. But in South Korea and Portugal, resistance to ABPC in E. coli is reportedly lower than that in this study (3.9%, 2/51, and 4.2%, 3/71, respectively) [ 7 , 20 ].…”

“…This study was part of a monitoring study of AMR bacteria isolated from healthy TB racehorse fecal samples in Japan. At the same time, the presence of extended-spectrum β-lactamase (ESBL)- and AmpC β-lactamase-producing bacteria and AMR enterococci was also investigated as per our previous reports [ 25 , 26 , 27 ]. Though this study used the same samples as our previous studies, the isolation and identification of E. coli were conducted using protocols that were independent from those used in our previous study about ESBL-producing E. coli that were isolated using a selective agar medium containing an antibiotic (1 µ g/m l cefotaxime).…”

“…E. coli ATCC 25922, Staphylococcus aureus ATCC 29213, and Enterococcus faecalis ATCC 29212 were used as quality control strains. Isolates that phenotypically showed resistance to at least three classes of antimicrobials were considered to be multidrug resistant (MDR) [ 27 ].…”

“…In most countries, information about the volume of antimicrobials used in equine medicine [ 31 ] and the availability of those that are pharmaceutically approved is limited [ 5 , 27 ]. The presence of AMR bacteria affects animal welfare and economically impacts businesses in the horse industry [ 2 ], but the occurrence of antimicrobial resistance varies greatly depending on the breeding style in the studied population (e.g., health conditions, breeding area, and feed).…”

Antimicrobial Resistance in Horses

“…In a similar cohort of healthy horses from Canada, the number of staff members and equestrian event participation were identified as risk factors for MDR E. coli shedding [ 13 ]. In a study from Japan, healthy racehorses were reported to be colonized with MDR ESBL/AmpC-producing Klebsiella pneumoniae [ 14 ]. Another unique horse population that AMR pathogens were recovered from was equine destined for human consumption in Spain, in which both nasal and fecal carriage of a highly virulent MRSA was detected [ 15 ].…”