Clonal dissemination of a CTX-M-15 beta-lactamase-producing Escherichia coli strain in the Paris area, Tunis, and Bangui

Abstract

One hundred twenty CTX-M-15-producing Escherichia coli strains isolated in 10 different hospitals from Paris (France), in the Hospital Charles Nicolle in Tunis (Tunisia), and in the Pasteur Institute in Bangui, Central African Republic (CAR), between 2000 and 2004 were studied. Eighty isolates, recovered from the three countries, were clonally related by repetitive extragenic palindromic PCR and pulsed-field gel electrophoresis. Various resistance profiles were identified among these clonal strains. After conjugation or electroporation of plasmids from E. coli strains representative of each profile and each geographic region, we observed seven resistance profiles in the recipient strains. Incompatibility typing showed that all the plasmids transferred from the clonal strains studied, except one, belonged to the incompatibility group FII. They all shared a multidrug resistance region (MDR) resembling the MDR region located in pC15-1a, a plasmid associated with an outbreak of a CTX-M-15-producing E. coli strain in Canada. They also shared the common backbone of an apparent mosaic plasmid, including several features present in pC15-1a and in pRSB107, a plasmid isolated from a sewage treatment plant. This study suggests that although the plasmid-borne blaCTX-M-15 gene could be transferred horizontally, its dissemination between France, Tunisia, and CAR was due primarily to its residence in an E. coli clone with a strong propensity for dissemination.

FIG. 1.

Schematic drawing showing the multidrug resistance region of pC15-1a (accession number AY458016) (3) and the position of the PCR targets with the primers listed in Table 2. Black arrow, IS26; light-gray arrow, tnpA; dark-gray arrow, tnpR.

FIG. 2.

Fingerprint of Inc FII plasmids harboring CTX-M-15 β-lactamase. (A) HpaI-digested plasmid profiles of transconjugants or electroporants producing CTX-M-type β-lactamases. (B) Southern blot analysis results of the same HpaI-digested plasmids, using the backbone probe. Lane M, DNA molecular weight marker II (Roche Diagnostics); lane 1, EpTN03; lane 2, TcTN36; lane 3, TcTN49; lane 4, TcER15; lane 5, EpLA2; lane 6, TcTN34; lane 7, EpPB01; lane 8, EpTU; lane 9, TcTN50.

FIG. 3.

Hybridization of HpaI-digested plasmids, using bla_CTX-M-15 (A) and bla_OXA-1 (B) probes associated to a DNA molecular weight marker II (Roche Diagnostics) probe. Lane M, DNA molecular weight marker II probe; lane 1, EpTN03; lane 2, TcTN36; lane 3, TcTN49; lane 4, TcER15; lane 5, EpLA2; lane 6, TcTN34; lane 7, EpPB01; lane 8, EpTU; lane 9, TcTN50.