High Prevalence of CTX-M-15-Producing O25b-ST131Escherichia coliClone in Bulgarian Hospitals

Abstract

According to the European Antimicrobial Resistance Surveillance System project results, Bulgaria has become one of the European countries with dramatically increasing rates of extended-spectrum beta-lactamase (ESBL) producers. The aim of this work was to investigate the epidemiology of ESBL-producing Escherichia coli clinical isolates in Bulgaria, collected from seven clinical centers in three towns, during two study periods: 2002-2003 and 2006-2009. For 193 ESBL-producing E. coli isolates random amplified polymorphic DNA (RAPD) analyses, phylogenetic typing, and screening for O25b-ST131 isolates were carried out. Antimicrobial susceptibility, ESBL-type and transferability of resistance determinants were analyzed. Four different ESBL-types, namely TEM-139, SHV-12, CTX-M-3, and CTX-M-15 were found. CTX-M-15 dominated, being found in 88% of the isolates. RAPD-typing revealed 35 types, among which type A dominated, comprising 65% of the isolates. Sixty-eight percent of the 193 isolates belonged to the O25b-ST131 clone, to the phylogenetic group B2, mostly showed RAPD-type A (92%) and were found in all participating hospitals. O25b-ST131 isolates predominantly produced CTX-M-15 (96%), and less SHV-12 (n=3) or TEM-139 (n=2). In conclusion, this study demonstrated for the first time the country-wide dissemination of a highly resistant B2 O25b-ST131 CTX-M-15 producing E. coli clone in Bulgaria.