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Published on: February 1, 2018
Metallo-beta-lactamase IMP-1 in Providencia rettgeri from two different hospitals in Japan
Katsuaki Shiroto1, Yoshikazu Ishii1, Soichiro Kimura1
1Department of Microbiology and Infectious Diseases, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, 143-8540 Tokyo, Japan 2Institute of Tropical Medicine, Nagasaki University, Japan 3Department of Clinical Laboratory, Mie University Hospital, Japan.
Abstract:
In 2002, 495 indole-positive proteae strains were isolated from patients at 60 hospitals in Japan. Nine indole-positive proteae strains had reduced susceptibility to imipenem (MIC > or = 8 microg ml(-1)) and were identified as Providencia rettgeri by BD Phoenix. Eight of the nine Prov. rettgeri isolates were confirmed as metallo-beta-lactamase producers by the double-disc synergy test. All the metallo-beta-lactamases were classified as IMP-1 by PCR and DNA sequence analysis. These bla(IMP-1) genes were encoded in the integron structure on conjugative plasmids. These plasmids could transfer from Prov. rettgeri clinical isolates to Escherichia coli ML4903 at a frequency between 1.5 x 10(-5) and 5.5 x 10(-7). The eight bla(IMP)-positive strains were isolated from two hospitals, and showed two different PFGE patterns, two different integron structures and two different incompatibility groups, which corresponded to the two hospitals. These results strongly suggest the possibility of nosocomial infections by bla(IMP-1)-producing Prov. rettgeri isolates.
Insights
Nine Providencia rettgeri strains showed reduced imipenem susceptibility in Japan. Eight produced IMP-1 metallo-beta-lactamase, transferable via plasmids, suggesting nosocomial infection risks.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Biology
Background:
- Indole-positive Proteae are common bacteria found in clinical settings.
- Antibiotic resistance, particularly to carbapenems like imipenem, is a growing global health concern.
- Metallo-beta-lactamases (MBLs) are a class of enzymes conferring resistance to a wide range of beta-lactam antibiotics.
Purpose of the Study:
- To investigate the prevalence and characteristics of imipenem-non-susceptible indole-positive Proteae strains in Japanese hospitals.
- To identify the specific resistance mechanisms and genetic elements responsible for imipenem resistance in these strains.
- To assess the potential for transmission and nosocomial spread of these resistant bacteria.
Main Methods:
- Isolation and identification of indole-positive Proteae strains from clinical samples.
- Antimicrobial susceptibility testing, including determination of imipenem minimum inhibitory concentrations (MICs).
- Detection of metallo-beta-lactamase production using phenotypic methods (double-disc synergy test).
- Molecular characterization including PCR for bla(IMP-1) gene detection, DNA sequencing, plasmid analysis, and pulsed-field gel electrophoresis (PFGE).
- Conjugation experiments to assess plasmid-mediated transfer of resistance.
Main Results:
- Nine out of 495 indole-positive Proteae strains exhibited reduced susceptibility to imipenem (MIC ≥ 8 μg/mL).
- These nine strains were identified as Providencia rettgeri.
- Eight of the nine Providencia rettgeri isolates were confirmed as metallo-beta-lactamase producers.
- All identified metallo-beta-lactamases were classified as IMP-1.
- The bla(IMP-1) genes were located on integrons within conjugative plasmids, transferable to Escherichia coli.
- The eight bla(IMP)-positive strains were isolated from two hospitals and displayed distinct genetic profiles (PFGE patterns, integron structures, incompatibility groups), correlating with their hospital of origin.
Conclusions:
- The study identified IMP-1 metallo-beta-lactamase-producing Providencia rettgeri as a cause of imipenem resistance in Japanese hospitals.
- The presence of bla(IMP-1) genes on transferable plasmids highlights the risk of horizontal gene transfer and dissemination.
- Distinct genetic profiles associated with specific hospitals suggest localized outbreaks or endemicity.
- These findings underscore the potential for nosocomial infections caused by these multidrug-resistant organisms and the need for vigilant surveillance and infection control measures.
