MOLECULAR CHARACTERIZATION OF MULTIDRUG-RESISTANT E. COLI ISOLATED FROM BACTEREMIA PATIENTS

Abstract

Background: Extraintestinal pathogenic Escherichia coli (ExPEC) bacteria have the ability to cause diverse and serious diseases, such as urinary tract infections (UTIs) and bacteremia; incidence of bacteremia is increasing globally. The emergence of multidrug resistance in E. coli is also becoming a global concern, with particular emphasis on E. coli sequence type (ST) 131, which is being increasingly reported in UTIs. Drug resistance is mediated by extended- spectrum β-lactamases (ESBLs), mainly of the CTX-M family, particularly CTX-M-15, and less frequently of the SHV and OXA families. Few studies are available regarding the characterization of E. coli strains causing bacteremia. Methods: We characterized 52 selected fluoroquinolones and cephalosporins-resistant E. coli isolates from bacteremia patients treated at Policlinico University Hospital (Palermo, Italy) over a 6-years period, with the aim of developing an epidemiologic profile of the population of ExPEC that causes bacteremia. Multiplex PCR to determine the phylogenetic group, multiplex ERIC PCR to analyze the epidemiological correlations, multiplex PCR detection of ESBL genes, multilocus sequence typing using the Achtman scheme (http://mlst.ucc.ie/ mlst/dbs/Ecoli), and virulence-associated gene (VAG) carriage screening by multiplex PCR were performed on isolates. Results: The 86.5% of our strains belonged to phylogenetic group B2, while the phylogenetic group D appeared to be under-represented (13.5%) and no strain belonged to group A nor B1. Clustering analysis by ERIC-PCR showed a high heterogeneity of the strains that did not allow a significant grouping and PCR screening for ESBL carriage showed significantly higher carriage for CTX-M 15. Multilocus sequence types were determined in all our bacteremia E. coli isolates: ST131 dominated and was significantly higher in prevalence (75%) followed by ST167, 58, 38, 744, 405, 453, 707 and 1447. VAGs screening of all isolates showed that the most represented were kpsM II and iutA coding for the capsule and an aerobactin (siderophore) receptor, respectively. Conclusions: Overall, our results show that ST131 is the predominant E. coli lineage among the 52 extraintestinal pathogenic E. coli (ExPEC) isolates from bacteremia patients included in this study. Our group B2 ExPEC ST131 isolates produce extended-spectrum b-lactamases, especially CTX-M-15, and almost all are resistant to fluoroquinolones. 42ND