Molecular characterization of imipenem-resistant Pseudomonas aeruginosa in Hiroshima, Japan
Masaru Ohara1, Shuntaro Kouda, Makoto Onodera
1Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan.
Abstract:
Pseudomonas aeruginosa showing resistance to imipenem were found in 100 of 1,058 strains (9.5%) from six hospitals (a-f) in Hiroshima City, Japan. Of the 100 strains, 14 (14%) were double disk synergy test positive using sodium mercaptoacetic acid disks, and 18 (18%) were bla(IMP-1) or bla(VIM-2) allele positive by polymerase chain reaction (PCR). Among 100 imipenem-resistant strains, 32 were categorized into multi-drug resistant strains, in which 13 were positive for the metallo-beta-lactamase gene. Fifty-one strains (51%) among the 100 imipenem-resistant strains had elevated RND efflux pump activity against levofloxacin. But only 6 of 51 strains were classified as multi-drug resistant strains. The pulsed field gel electrophoresis analysis of the Spe I-digested DNA from the 100 isolates suggested not only clonal spread but spread of heterogeneous clones started to contribute to the prevalence of metallo-beta-lactamase producing P. aeruginosa strains in Japanese hospitals.
Insights
Imipenem-resistant Pseudomonas aeruginosa strains are prevalent in Japanese hospitals. Metallo-beta-lactamase genes and efflux pumps contribute to multidrug resistance, indicating clonal and heterogeneous spread.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Pseudomonas aeruginosa is a significant opportunistic pathogen.
- Imipenem resistance in P. aeruginosa is a growing global health concern.
- Metallo-beta-lactamases (MBLs) are a major mechanism of carbapenem resistance.
Purpose of the Study:
- To investigate the prevalence and characteristics of imipenem-resistant Pseudomonas aeruginosa in Hiroshima City hospitals.
- To identify the genetic mechanisms, including MBL genes and efflux pumps, contributing to resistance.
- To understand the dissemination patterns of resistant strains.
Main Methods:
- Phenotypic detection of imipenem resistance.
- Double disk synergy test for MBL detection.
- Polymerase chain reaction (PCR) for bla(IMP-1) and bla(VIM-2) genes.
- Assessment of multidrug resistance (MDR) and RND efflux pump activity.
- Pulsed field gel electrophoresis (PFGE) for strain typing.
Main Results:
- 9.5% of P. aeruginosa strains exhibited imipenem resistance (100/1058).
- 18% of resistant strains carried bla(IMP-1) or bla(VIM-2) genes.
- 32% of imipenem-resistant strains were multidrug-resistant, with 13% positive for MBL genes.
- 51% of resistant strains showed elevated RND efflux pump activity against levofloxacin.
- PFGE suggested both clonal and heterogeneous spread of MBL-producing P. aeruginosa.
Conclusions:
- Imipenem resistance in P. aeruginosa is a significant issue in Hiroshima City hospitals.
- MBL genes and RND efflux pumps are key contributors to resistance and MDR.
- The spread of MBL-producing P. aeruginosa involves both clonal and heterogeneous mechanisms, necessitating enhanced surveillance and control strategies.
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