Genetic features of antimicrobial drug-susceptible extraintestinal pathogenicEscherichia colipandemic sequence type 95

Abstract

Extraintestinal pathogenic Escherichia coli (ExPEC) belonging to multilocus sequence type 95 (ST95) is one of the most widespread ExPEC lineages associated with bloodstream infections (BSI) and urinary tract infections (UTI). In contrast to other widespread ExPEC sequence types, a large proportion ST95 strains remains susceptible to all antimicrobial agents used to treat BSI or UTI. We aimed to identify genomic features of ST95 associated with persistent drug susceptibility. We conducted a genome-wide association study of 80 ExPEC ST95 isolates from patients with BSI or UTI in Northern California, and 1669 ST95 isolates deposited in the Enterobase database. Of the total of 1749 ST95 isolates, we compared whole-genome sequences of 887 drug-susceptible strains and 862 strains resistant to one or more drugs (defined genotypically as strains harboring drug-resistance genes annotated in the ResFinder database) to identify genetic features associated with strains devoid of drug-resistance genes. By a genome-wide association study of 553 UTI and BSI ST95 isolates, we found 44 accessory genes significantly associated with drug susceptibility, six of which encoded hypothetical proteins. Fifteen of these were not found in any of the WGSs of ST131 ExPEC strains, which are frequently multidrug-resistant, and eight of these genes were annotated to encode transporter or transfer systems. These findings highlight the potential mechanisms by which ST95 strains may resist the acquisition of mobile DNA elements carrying drug-resistance genes.ImportanceDespite the increasing prevalence of antibiotic resistance in Escherichia coli strains that cause common infections such as urinary tract and bloodstream infections, a major pandemic lineage of extraintestinal pathogenic E. coli ST95 has remained susceptible to most drugs used to treat these infections. We compared genomes of 1749 ST95 isolates to identify genetic features that may explain why most strains of ST95 resist becoming drug-resistant. Identification of such genomic features could contribute to the development of novel strategies to prevent the spread of antibiotic-resistant genes and devise new measures to control antibiotic-resistant infections.