Plasmid-mediated cephalosporin resistance in CMY-2-producing Escherichia coli isolated from ready-to-eat cilantro.

​​There has been an increasing number of global reports documenting the high prevalence of multidrug-resistant (MDR) strains in the environment, highlighting the role of food as a reservoir of both commensal and pathogenic Escherichia coli capable of harboring and transmitting antimicrobial resistance genes. Fresh vegetables can become contaminated with bacteria during production, handling, and distribution and may consequently harbor substantial bacterial loads. Because these products are often consumed raw or with minimal processing, inadequate washing and disinfection practices may allow bacteria to persist on their surfaces, including MDR strains. The presence of antimicrobial-resistant E. coli in ready-to-eat vegetables is of concern because these bacteria may harbor virulence and antimicrobial resistance determinants, as well as mobile genetic elements that facilitate their dissemination. Consequently, characterization of their resistome, virulome, and plasmidome can provide comprehensive insights into their pathogenic potential, resistance profiles, and the genetic mechanisms that may contribute to the spread of antimicrobial resistance along the food chain. This study focuses on two E. coli strains, A65EC and A134EC, isolated from ready-to-eat cilantro. Both strains were phenotypically characterized as MDR and AmpC-type β-lactamase producers, a capacity associated with the presence of the blaCMY-2 gene on an IncI1 and p0111 plasmid, respectively. In addition, A65EC belonging to ST746 presented three additional plasmids characterized as conjugative or mobilizable, harboring the resistance genes aadA2, blaTEM-103, sul1, dfrA12, dfrA14, tetA and qacEΔ1. Meanwhile, A134EC corresponding to ST10 showed three conjugative plasmids and one mobilizable plasmid carrying the genes aadA5, aac(3)-Ild, dfrA17, qacEΔ1, sul3, mefB, floR, estT and fosA2. Moreover, 19 virulence genes were identified, of which nine (aslA, fimH, nlpl, iss, sitA, terC, hlyE, cia, and anr) were shared by both strains. This is the first report of blaCMY-2-bearing strains isolated from green leafy vegetables, and we describe the presence of the fosA2 gene harbored on a conjugative plasmid. The detection of multidrug-resistant strains with the genetic potential to transfer resistance determinants in fresh produce is a concerning finding. It underscores the urgent need for surveillance and monitoring systems in vegetables to better elucidate the transmission pathways of resistance and virulence genes across diverse ecological niches.