High Expression of Metallo-beta-Lactamase Contributed to the Resistance to Carbapenem in Clinical Isolates of Pseudomonas aeruginosa from Baotou, China
INFECTION AND DRUG RESISTANCE
Authors: Xu, Yanfeng; Niu, Haiying; Hu, Tongping; Zhang, Lixia; Su, Shanna; He, Huijie; Wang, Huimin; Zhang, Dong
Abstract
Background: Bacterial resistance to antibiotics has become a major public health concern. This study aimed to determine the resistance mechanisms to carbapenem in clinical isolates of Pseudomonas aeruginosa. Methods: A total of 62 clinical isolates of carbapenem-resistant P aeruginosa (CRPA) were collected from 2015 to 2017. Imipenem (IPM)-EDTA disk synergy test was used to screen strains that produced metallo-beta-lactamase. In addition, the genes for outer membrane protein OprD2, metallo-beta-lactamase and mexR gene were amplified and sequenced. Expression of mexA was detected by real-time PCR. Results: Disk synergy test showed that 51.6% (32/62) of the strains were positive for metallo-beta-lactamase. PCR showed that 84.4% of the strains were SIM-positive (27/32), 15.6% of the strains were IMP-positive (5/32), and 12.5% of the strains were VIM-positive (4/32). SPM-positive and GIM-positive strains were not detected. In addition, 5 of the 62 strains had small deletions and/or point mutations in OprD2. Three strains had a high expression of mexA, while eight strains were positive for the regulatory gene mexR with no mutations detected by DNA sequencing. Conclusion: Expression of metallo-beta-lactamase is the main resistance mechanism of P. aeruginosa to carbapenem. Mutations in OprD2 and/or the overexpression of efflux pump MexAB-OprM may contribute to P aeruginosa resistance to carbapenem.
Integrated chromosomal and plasmid sequence analyses reveal diverse modes of carbapenemase gene spread among Klebsiella pneumoniae
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Authors: David, Sophia; Cohen, Victoria; Reuter, Sandra; Sheppard, Anna E.; Giani, Tommaso; Parkhill, Julian; Rossolini, Gian Maria; Feil, Edward J.; Grundmann, Hajo; Aanensen, David M.
Abstract
Molecular and genomic surveillance systems for bacterial pathogens currently rely on tracking clonally evolving lineages. By contrast, plasmids are usually excluded or analyzed with low-resolution techniques, despite being the primary vectors of antibiotic resistance genes across many key pathogens. Here, we used a combination of long- and short-read sequence data of Klebsiella pneumoniae isolates (n = 1,717) from a European survey to perform an integrated, continent-wide study of chromosomal and plasmid diversity. This revealed three contrasting modes of dissemination used by carbapenemase genes, which confer resistance to last-line carbapenems. First, blaOXA-48-like genes have spread primarily via the single epidemic pOXA-48-like plasmid, which emerged recently in clinical settings and spread rapidly to numerous lineages. Second, bla(VIM) and bla(NDM) genes have spread via transient associations of many diverse plasmids with numerous lineages. Third, bla(KPC) genes have transmitted predominantly by stable association with one successful clonal lineage (ST258/512) yet have been mobilized among diverse plasmids within this lineage. We show that these plasmids, which include pKpQIL-like and IncX3 plasmids, have a long association (and are coevolving) with the lineage, although frequent recombination and rearrangement events between them have led to a complex array of mosaic plasmids carrying bla(KPC). Taken altogether, these results reveal the diverse trajectories of antibiotic resistance genes in clinical settings, summarized as using one plasmid/multiple lineages, multiple plasmids/multiple lineages, and multiple plasmids/one lineage. Our study provides a framework for the much needed incorporati on of plasmid data into genomic surveillance systems, an essential step toward a more comprehensive understanding of resistance spread.
COA
Certificate of Analysis
