Abstract
In our previous study, extended spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBLEC) were isolated from healthy Thoroughbred racehorse feces samples in Japan. Some ESBL genes were predicted to be located on the conjugative plasmid. PCR-based replicon typing (PBRT) is a useful method to monitor and detect the association of replicons with specific plasmid-borne resistant genes. This study aimed to evaluate the plasmid replicon associated with ESBLEC isolated from healthy Thoroughbred racehorses at Japan Racing Association Training Centers in Japan. A total of 24 ESBLECs isolated from 23 (10.8%) individual Thoroughbred racehorse feces samples were used in this study. ESBL gene transfer was performed using a conjugation assay. Then, replicon types of ESBLEC isolates and their transconjugants were determined using PBRT. Pulsed-field gel electrophoresis (PFGE) was performed to look at the clonality of the ESBLECs isolates. ESBLECs were detected from 10.8% of healthy Thoroughbred racehorses. The blaCTX-M-2 was identified as the dominant type of ESBL gene, followed by blaCTX-M-1 and blaTEM-116. In this study, only the blaCTX-M-2 and the IncI1 plasmid were transferred to transconjugants. The PFGE results showed that ESBL genes were distributed in diversity of ESBLECs. This finding suggested that the IncI1 plasmid was associated with the dissemination of blaCTX-M-2 in Thoroughbred racehorses in Japan.
Highlights
The emergence of resistance to third-generation cephalosporin, mediated mainly by extended spectrum β-lactamase (ESBL), has become a major health problem [1]
24 ESBL-producing Escherichia coli (ESBLEC) isolated from 23 (10.8%) individual Thoroughbred racehorse feces samples were identified genetically between April 2017 and August 2018
Horses can serve as a natural reservoir of antibiotic-resistant microorganisms, a characteristic which has implications on the health, treatment efficiency and epidemiological safety of people working in close contact with horses [13]
Summary
The emergence of resistance to third-generation cephalosporin, mediated mainly by extended spectrum β-lactamase (ESBL), has become a major health problem [1]. CTX-M types have been grouped into five clusters (CTX-M-1, CTX-M-2, CTX-M-8, CTX-M-9, and CTX-M-25) and over 172 CTX-M types have been reported [4] This massive worldwide dissemination has been described as the “CTX-M pandemic” [5]. The rapid spread of ESBL genes is mostly due to their location on the plasmid and the ease of transmission between bacteria [5,6,7,8]. Another reason for this increase is the co-resistance phenomenon
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