Characterization of antibiotic resistance and bacteriocin genes on plasmids in successful clones of E. coli.. Virulence and bacteriocin of Escherichia coli ST131 and other E. coli lineages.

Although extensively studied, Escherichia coli ST131 still is a clinical challenge due to its multidrug-resistant profile and successful global spread. They are often associated with complicated infections, particularly urinary tract infections (UTIs), due to the presence of resistance and virulence genes. Among the latter, bacteriocins play an important role to outcompete other microorganisms present. Most bacteriocins are encoded by genes located on plasmids and are highly variable among E. coli. Here, we characterized three bacteriocin-encoding plasmids found in isolates of hospitalized patients suffering from a UTI using both short-read and long-read sequencing. Identified bacteriocins (n=4) were colicin Ia, Ib, and E1, and microcin V. Interestingly, the plasmid carrying colicin Ib harbored he β-lactamase gene CMY-2, and the plasmid carrying the colicin Ia and microcin V had several other resistance genes inferring resistance to different classes of antibiotics. Although plasmids encoding colicin E1 are known to spread antibiotic resistance among Enterobacteriaceae we did not detect any resistance genes in such plasmid identified in one of our isolates. To investigate if the potential transmission range of the E1 colicin encoding plasmid is influenced by the presence of a resistance gene, we constructed a transformant strain containing a plasmid that had both the colicin E1 and blaCMY-2 genes. No difference in the transmission range was found for transformants compared to wild-type strains. In addition, also no difference in fitness was found between the strains. We also examined if the presence of plasmids encoding the specific bacteriocin altered the virulence potential of the isolates. No statistically significant difference was found in the adhesion and invasion ability among the bacteriocin producing and not-producing isolates. Bacteriocin-producing isolates from both ST131 and non-ST131 lineages were able to inhibit the growth of other E. coli isolates including isolates of the ST131 lineage that are normally not susceptible to bacteriocins. In summary, the presence of bacteriocin carrying plasmids gives additional advantages for already highly virulent and resistant ST131 isolates, improving the ability of these isolates to compete with other microbiota for a niche and thereby increasing the risk of infection.