bla SED-1 beta-lactamase-producing Citrobacter sedlakii isolated from horses and genomic comparison with human-derived isolates.

AIMS: We aim to detect beta-lactamase-producing Citrobacter sedlakii from horses and compare the genomic characteristics with isolates from humans.Methods and Result: We characterized phenotypically and genotypically nine C. sedlakii isolates from the feces of horses and then compared them to human-derived isolates using whole genome sequencing and phylogenomic methods. Seven isolates (7/9) were ampicillin-resistant, while at least one isolate was resistant to ceftriaxone, gentamicin, meropenem, and streptomycin. All nine isolates were carriers of the chromosomal-mediated blaSED-1  beta-lactamase gene which confer resistance to ampicillin. One isolate was positive for the mcr-9 gene that confers resistance to colistin, and another isolate had the aac(6')-lid gene that confers resistance to aminoglycosides. Seven isolates (7/9) were carriers of genes that confer metal resistance to copper, silver, and arsenic. Phylogenetically, two horse-derived isolates clustered together with two human-derived isolates from the NDARO database. CONCLUSION: The results from our study provide insight into the antimicrobial susceptibility of C. sedlakii in horses which was previously lacking, and the specific beta-lactamase gene mediating resistance.

Genomic Characterization of Fecal Escherichia coli Isolates with Reduced Susceptibility to Beta-Lactam Antimicrobials from Wild Hogs and Coyotes.

This study was carried out to determine the antimicrobial resistance (AMR) genes and mobile genetic elements of 16 Escherichia coli isolates-with reduced susceptibility to ceftazidime and imipenem-that were recovered from the fecal samples of coyotes and wild hogs from West Texas, USA. Whole-genome sequencing data analyses revealed distinct isolates with a unique sequence type and serotype designation. Among 16 isolates, 4 isolates were multidrug resistant, and 5 isolates harbored at least 1 beta-lactamase gene (blaCMY-2, blaCTX-M-55, or blaCTX-M-27) that confers resistance to beta-lactam antimicrobials. Several isolates carried genes conferring resistance to tetracyclines (tet(A), tet(B), and tet(C)), aminoglycosides (aac(3)-IId, ant(3″)-Ia, aph(3')-Ia, aph(3″)-lb, aadA5, and aph(6)-ld), sulfonamides (sul1, sul2, and sul3), amphenicol (floR), trimethoprim (dfrA1 and dfrA17), and macrolide, lincosamide, and streptogramin B (MLSB) agents (Inu(F), erm(B), and mph(A)). Nine isolates showed chromosomal mutations in the promoter region G of ampC beta-lactamase gene, while three isolates showed mutations in gyrA, parC, and parE quinolone resistance-determining regions, which confer resistance to quinolones. We also detected seven incompatibility plasmid groups, with incF being the most common. Different types of virulence genes were detected, including those that enhance bacterial fitness and pathogenicity. One blaCMY-2 positive isolate (O8:H28) from a wild hog was also a Shiga toxin-producing E. coli and was a carrier of the stx2A virulence toxin subtype. We report the detection of blaCMY-2, blaCTX-M-55, and blaCTX-M-27 beta-lactamase genes in E. coli from coyotes for the first time. This study demonstrates the importance of wildlife as reservoirs of important multi-drug-resistant bacteria and provides information for future comparative genomic analysis with the limited literature on antimicrobial resistance dynamics in wildlife such as coyotes.