Multiple acquisitions of CTX-M plasmids in the rare D2 genotype of Escherichia coli provide evidence for convergent evolution.
Over the last decade, CTX-M enzymes have become the most prevalent extended-spectrum beta-lactamases (ESBLs) worldwide, mostly in Escherichia coli, causing a major health problem. An epidemiological relationship has been established between a rare genotype of E. coli, the D(2) genotype, and the presence of CTX-M genes. We investigated this striking association by exploring the genetic backgrounds of 18 D(2) genotype CTX-M-producing strains and of the plasmids encoding CTX-M enzymes. The 18 strains had different genetic backgrounds, as assessed by multilocus sequence and O typing, and were associated with various plasmids bearing diverse CTX-M genes. The region encompassing the genetic marker of the D(2) genotype (TSPE4.C2) was not correlated with the presence of CTX-M genes. CTX-M-producing D(2) strains had far fewer virulence factors than a control group of 8 non-ESBL-producing D(2) strains, and an inverse relationship was found between the number of co-resistances associated with the CTX-M gene and the number of virulence factors found in the strain. These findings provide evidence for multiple acquisitions of plasmids carrying CTX-M genes in different D(2) genotype strains. They strongly suggest that convergent evolution has occurred, and indicate that there has been selection for the association of a specific genetic background of the strain and the CTX-M gene. This fine-tuning of the relationship between the D(2) genotype and CTX-M genes presumably increases the fitness of the strain, indicating a role for the host cell in the acquisition and dissemination of CTX-M genes.
Deschamps
Catherine
C
AP-HP, Hôpital Louis Mourier, Service de Microbiologie-Hygiène, Colombes, France.|INSERM U722 and Université Denis Diderot-Paris 7, Faculté de Médecine, Site Xavier Bichat, Paris, France.
Clermont
Olivier
O
INSERM U722 and Université Denis Diderot-Paris 7, Faculté de Médecine, Site Xavier Bichat, Paris, France.
Hipeaux
Marie Claire
MC
AP-HP, Hôpital Louis Mourier, Service de Microbiologie-Hygiène, Colombes, France.
Arlet
Guillaume
G
AP-HP, Hôpital Tenon, Service de Bactériologie-Hygiène, Paris, France.|EA 2392, Université Pierre et Marie Curie-Paris 6, Faculté de Médecine, Site Saint-Antoine, Laboratoire de Bactériologie, Paris, France.
Denamur
Erick
E
INSERM U722 and Université Denis Diderot-Paris 7, Faculté de Médecine, Site Xavier Bichat, Paris, France.
Branger
Catherine
C
AP-HP, Hôpital Louis Mourier, Service de Microbiologie-Hygiène, Colombes, France.|INSERM U722 and Université Denis Diderot-Paris 7, Faculté de Médecine, Site Xavier Bichat, Paris, France.
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D005838:Genotype; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D001618:beta-Lactamases