bla(IMP) and bla(VIM) mediated carbapenem resistance in Pseudomonas and Acinetobacter species in India
M Shanthi Amudhan1, Uma Sekar, Arunagiri Kamalanathan
1Sri Ramachandra Medical College and Research Institute, Porur, Chennai, India. amu_shanthi@yahoo.co.in
Introduction:
The emergence and rapid spread of blaIMP and blaVIM metallo-beta-lactamase (MBL) producing Gram-negative bacteria causing nosocomial infections are of concern worldwide due to limited treatment options.
Methodology:
A total of 179 nonreplicate, consecutive, carbapenem resistant Pseudomonas aeruginosa (61), Acinetobacter baumannii (116), Acinetobacter lwoffii (1) and Pseudomonas stutzeri (1) isolated from patients hospitalized for 48 hours or more were included in the study. The minimum inhibitory concentrations (MIC) to imipenem and meropenem were determined and interpreted according to Clinical Laboratory Standards Institute guidelines. The Modified Hodge Test (MHT) and inhibitor potentiated disk diffusion tests with ethylenediaminetetraacetic acid (EDTA) were used for screening of carbapenamases and MBL production respectively. Polymerase chain reaction (PCR) was performed for the detection of MBL (blaVIM and blaIMP) genes. Gene sequencing was performed for representative isolates.
Results:
MHT was positive in 94.4% (n = 169). MBL screening with EDTA was positive in 80.4% (n = 144). MBL genes bla VIM and bla IMP were detected in 92 (51.4%) isolates. Bla VIM alone was detected in 89 isolates while two isolates had bla IMP alone. One isolate had both bla VIM and bla IMP. Among the P. aeruginosa, 36 carried the MBL gene. In A. baumannii, 54 carried the MBL gene. Bla VIM was found in P. stutzeri and A. lwoffii isolates.
Conclusion:
Carbapenem resistance in P. aeruginosa and A. baumannii is chiefly mediated by MBL production. The common MBL gene is the blaVIM.
Insights
Metallo-beta-lactamase (MBL) genes, primarily blaVIM, are common in carbapenem-resistant Pseudomonas aeruginosa and Acinetobacter baumannii, contributing to serious nosocomial infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Metallo-beta-lactamase (MBL) producing Gram-negative bacteria, specifically blaIMP and blaVIM, are a growing global concern for nosocomial infections.
- Limited treatment options exist for infections caused by these multidrug-resistant organisms.
Purpose of the Study:
- To investigate the prevalence of metallo-beta-lactamase (MBL) genes (blaVIM and blaIMP) in carbapenem-resistant Gram-negative bacteria.
- To identify the specific MBL genes responsible for carbapenem resistance in Pseudomonas aeruginosa and Acinetobacter baumannii.
Main Methods:
- Analyzed 179 carbapenem-resistant isolates of Pseudomonas aeruginosa and Acinetobacter baumannii.
- Determined minimum inhibitory concentrations (MICs) for imipenem and meropenem.
- Utilized Modified Hodge Test (MHT), ethylenediaminetetraacetic acid (EDTA) disk diffusion, and Polymerase Chain Reaction (PCR) to detect MBL production and genes.
Main Results:
- Metallo-beta-lactamase (MBL) genes (blaVIM and blaIMP) were detected in 51.4% (92/179) of isolates.
- The blaVIM gene was the most prevalent MBL gene, found in 89 isolates.
- MBL production was confirmed in 80.4% of isolates, with blaVIM identified in Pseudomonas aeruginosa, Acinetobacter baumannii, Pseudomonas stutzeri, and Acinetobacter lwoffii.
Conclusions:
- Metallo-beta-lactamase (MBL) production is a primary mechanism of carbapenem resistance in Pseudomonas aeruginosa and Acinetobacter baumannii.
- The blaVIM gene is the predominant MBL gene circulating in these nosocomial pathogens.
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