Genetic background of Escherichia coli and extended-spectrum beta-lactamase type

Abstract

To assess the implication of the genetic background of Escherichia coli strains in the emergence of extended-spectrum-Beta -lactamases (ESBL), 55 TEM-, 52 CTX-M-, and 22 SHV-type ESBL-producing clinical isolates involved in various extraintestinal infections or colonization were studied in terms of phylogenetic group, virulence factor (VF) content (pap, sfa/foc, hly, and aer genes), and fluoroquinolone resistance. A factorial analysis of correspondence showed that SHV type, and to a lesser extent TEM type, were preferentially observed in B2 phylogenetic group strains that exhibited numerous VFs but were fluoroquinolone-susceptible, whereas the newly emerged CTX-M type was associated with the D phylogenetic group strains that lacked VF but were fluoroquinolone-resistant. Thus, the emergence of ESBL-producing E. coli seems to be the result of complex interactions between the type of ESBL, genetic background of the strain, and selective pressures in ecologic niches.

Figure

Graphic representation of the results of the factorial analysis of correspondence carried out with whole data from the 129 Escherichia coli strains. A) Projections of the variables on the F1/F2 plane: phylogenetic group and subgroups (A₀, A₁, B1, B2₂, B2₃, D₁, and D₂), type of extended-spectrum β-lactamase (ESBL) (TEM, SHV, CTX-M), virulence factors (pap, sfa, hly, aer), and the source infection (inf) or colonization (col). B) Projections of the variables on the F1/F2 plane: phylogenetic group and subgroups (A₀, A₁, B1, B2₂, B2₃, D₁, and D₂), type of ESBL (TEM, SHV, CTX-M), and ciprofloxacin resistance (cipR) or the ciprofloxacin susceptibility (cipS).