Abstract
Simple SummaryThe spread and development of extended spectrum beta-lactamase (ESBL)-mediated antimicrobial resistance is a significant concern in healthcare with impacts to animal and public health alike. While the occurrence of the ESBL phenotype in Escherichia coli has been investigated in depth by numerous studies, there is still a lack of information regarding ESBL-producing bacterial isolates from clinical specimens of equine origin. In this study, we investigated the incidence of ESBL-producing E. coli in hospitalized horses. Overall, 207 E. coli isolates were analyzed for their antimicrobial susceptibility and 13 ESBL-producing E. coli isolates were genotypically characterized. Seven out of the 13 E. coli isolates were found to harbor the resistance genes blaCTX-M-1 or blaSHV-1 and a novel beta-lactamase TEM gene variant, blaTEM-233 was discovered. Furthermore, despite being phenotypically susceptible to tested carbapenems, 1 out of 13 E. coli isolates was PCR-positive for the carbapenemase gene, blaIMP-1. The latter is an alarming finding because the presence of carbapenemase resistance genes in equine pathogens is extremely rare. In conclusion, equines can be reservoirs for ESBL-producing Enterobacteriaceae, and further investigation into this species group is necessary to understand their impact in the spread and development of antibiotic resistance genes.Escherichia coli isolates were recovered from clinical specimens of equine patients admitted to the Texas A&M Veterinary Medical Teaching Hospital over a five-year period. Ceftiofur resistance was used as a marker for potential extended-spectrum beta-lactamase (ESBL)-activity, and of the 48 ceftiofur-resistant E. coli isolates, 27.08% (n = 13) were phenotypically ESBL-positive. Conventional PCR analysis followed by the large-scalebla Finder multiplex PCR detected the ESBL genes, CTX-M-1 and SHV, in seven out of the 13 isolates. Moreover, beta-lactamase genes of TEM-1-type, BER-type (AmpC), and OXA-type were also identified. Sequencing of these genes resulted in identification of a novel TEM-1-type gene, called blaTEM-233, and a study is currently underway to determine if this gene confers the ESBL phenotype. Furthermore, this report is the first to have found E. coli ST1308 in horses. This subtype, which has been reported in other herbivores, harbored the SHV-type ESBL gene. Finally, one out of 13 E. coli isolates was PCR-positive for the carbapenemase gene, blaIMP-1 despite the lack of phenotypically proven resistance to imipenem. With the identification of novel ESBL gene variant and the demonstrated expansion of E. coli sequence types in equine patients, this study underscores the need for more investigation of equines as reservoirs for ESBL-producing pathogens.
Highlights
In 2014, the World Health Organization (WHO) released a review that affirmed antimicrobial resistance as a major global threat, with a predicted impact of 100 trillion dollars in economic losses and 10 million deaths attributable to resistant bacteria by 2050 [1,2]
Among the third-generation cephalosporins, the lowest proportion of resistance was observed for the E. coli isolates tested against ceftazidime, with only 3.25% (4/123) of the isolates being resistant to this antimicrobial
The results of the present study demonstrated that 27.08% of the isolates screened with ceftiofur expressed the extended-spectrum beta-lactamase (ESBL)-positive phenotype
Summary
In 2014, the World Health Organization (WHO) released a review that affirmed antimicrobial resistance as a major global threat, with a predicted impact of 100 trillion dollars in economic losses and 10 million deaths attributable to resistant bacteria by 2050 [1,2]. The production of beta-lactamases, a rapidly evolving class of hydrolytic enzymes that inactivate beta-lactam antibiotics, is a significant mechanism of antimicrobial resistance against penicillins and cephalosporins [3–. The possibility of cross-species transmission of ESBL-positive bacterial strains directly represents a health hazard for humans, especially equine handlers and veterinary staff [15,17,18]. Despite this significant problem, information on the occurrence and genetic characterization of ESBL-positive E. coli isolated from horses is lacking [3,19,20]. The objective of the present work was to examine the proportion and genetic diversity of ESBL-positive E. coli in clinical specimens of equine origin
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