Occurrence of OXA-48 Carbapenemase and Other β-Lactamase Genes in ESBL-Producing Multidrug Resistant Escherichia coli from Dogs and Cats in the United States, 2009-2013

Objective: The aim of this study was to explore the occurrence and molecular characterization of extended-spectrum beta-lactamases (ESBL), plasmid-mediated AmpC beta-lactamase (pAmpC) and carbapenemases among ESBL-producing multidrug resistant (MDR) Escherichiacoli from dogs and cats in the United States. Methods: Of 2443 E.coli isolated from dogs and cats collected between August 2009 and January 2013, 68 isolates were confirmed as ESBL-producing MDR ones. PCR and sequencing were performed to identify beta-lactamases and plasmid-mediated quinolone resistance (PMQR) genes, and shed light on the virulence gene profiles, phylogenetic groups and ST types. Results: Phylogenic group D and B2 accounted for 69.1% of the isolates. 50 (73.5%) isolates carried CTX-MESBL gene, and the most predominant specific CTX-M subtype identified was bla(CTX-M-15) (n=33), followed by bla(CTX-M-1) (n=32), bla(CTX-M-123)(n=27), bla(CTX-M-9)(n=19) and bla(CTX-M-14)(n=19), and bla(CTX-M-123) was firstly reported in E.coli isolates in the United States alone or in association. Other beta-lactamase genes bla(TEM), bla(SHV), bla(OXA-48), and bla(CMY-2) were detected in 41.2, 29.4, 19.1, and 17.6% of 68 ESBL-producing MDR isolates, respectively. The bla(TEM) and bla(SHV) genes were classfied as ESBLs with the exception of the bla(TEM-1) gene. Additionally, 42.6% (29/68) of isolatesco-expressed bla(CTX-M-15) and PMQR gene aac(6')-Ib-c. The overall occurrence of virulence genes ranged from 11.8 (ireA) to 88.2% (malX), and most of virulence genes were less frequent among CTX-M-producing isolates than non-CTX-M isolates with the exception of malX and iutA. The 68 isolates analyzed were assigned to 31 STs with six being novel. Three pandemic clonal lineages ST131 (n=10), ST648 (n=9), and ST405 (n=9) accounted for more than 41% of the investigated isolates, and ST648 and ST405 of phylogenetic D were firstly reported in E.coli from dogs and cats in the United States. Conclusion: bla(CTX-M-123) of ESBLs and carbapenemase blaOXA-48 were firstly reported in ESBL-producing MDR E.coli from dogs and cats in the United States, and ST131, ST648, and ST405 were the predominant clonal groups.