Distribution of β-Lactamase Genes and Genetic Context of in Clinical Carbapenemase-Producing Isolates.

BACKGROUND

This study was designed to characterize the dissemination mechanism and genetic context of carbapenemase (KPC) genes in carbapenem-resistant (CRKP) isolates.

METHODS

A retrospective analysis was performed on CRKP strains isolated from a teaching hospital of Wenzhou Medical University during 2015-2017. Polymerase chain reaction (PCR)-based amplification and whole-genome sequencing (WGS) were used to analyze the genetic context of the gene. Conjugation experiments were performed to evaluate the transferability of -bearing plasmids. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were performed to investigate the clonal relatedness of -producing strains.

RESULTS

The gene was identified from 13.61% (40/294) of clinical isolates. Three different sequence types (ST11, ST15 and ST656) and 5 PFGE subtypes (A to E) were classified among them. ST11 was the dominant sequence type (92.50%, 37/40). Plasmid-oriented antibiotic resistance genes, such as extended spectrum-β-lactamases (ESBLs) and other antimicrobial resistance genes, were also found in KPC-positive (KPC-) isolates. Mapping PCR and genomic sequencing revealed that the -bearing sequence regions, which are related to different mobile elements, including Tn1721- and IS26-based transposons, were mainly located in but not restricted to IncFII-like plasmids and were structurally divergent.

CONCLUSION

The genes related to divergent mobile genetic elements encoded on transferable plasmids may transfer widely, facilitating the spread of carbapenem resistance among bacteria with different genetic backgrounds. The dissemination of -bearing plasmids that collectively carry additional multidrug resistance genes has caused widespread public concern, further limiting the antibiotics available to treat infections caused by KPC-producing pathogens.