IncFIB plasmids carrying the resistance gene blaCTX-M-15 in ESBL-producing Escherichia coli clones from pediatric patients

Introduction: The emergence of extended-spectrum 13-lactamases (ESBLs)-producing Escherichia colt clones are a public health concern worldwide. Scarce information does exist about the spread of ESBLs-producing E. colt in pediatric patients from developing countries. Methodology: E colt strains were analyzed by multilocus-sequence-typing, pulsed-field-gel-electrophoresis and phylogenetic group. The antimicrobial-resistance genes were detected by PCR, and plasmid content by the PCR-based replicon-typing. Horizontal transfer was tested by conjugation and the location of the blacrx-M-15 gene by Southern blot hybridization. Results: Thirty-two cefotaxime-resistant E. colt were recovered. Eleven of them were ESBL-producing isolates, which were well characterized and ascribed to seven sequence types and five phylogroups. The ESBL CIX-M-15 was the most prevalent enzyme (9 of 11). Plasmids of variable sizes (40-220 kb) were visualized, and the incompatibility (Inc) group FIB plasmid-replicon was detected in the ESBL strains and transferred by conjugation in 45.45% of them. Plasmid-borne toxin-antitoxin systems were the most frequently detected systems, strongly associated to IncF plasmids. The CTX-M-15-encoding gene was located on IncFIB plasmids. Conclusions: Even though a small number of ESBL-producing strains was recovered, we evidenced that IncFIB plasmids carry the b/acrx-m-15 gene, highlighting the role of IncF-type plasmids in facilitating the spread and maintenance of ESBL-encoding genes, which further favors the rapid increase of the antimicrobial resistance dissemination in disease-causing E. colt strains in pediatric patients.

Automated summary

This study identified ESBL-producing Escherichia coli strains in pediatric patients from developing countries, and found that these strains can be transmitted through plasmids. The ESBL gene was located on IncFIB plasmids, and the plasmid-borne toxin-antitoxin systems were closely associated with IncF plasmids.