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Emergence of OptrA Gene Mediated Linezolid Resistance among Enterococcus Faecium: A Pilot Study from a Tertiary Care
Vandana Rani1,2, Ajit Prakash3, Mohammad Amin-Ul Mannan1,4
1Department of Molecular Biology and Genetic Engineering, School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India.
Abstract:
E. faecium is the third most common cause of nosocomial infections. Linezolid (LNZ) is a reserve antibiotic recommended for infections caused by vancomycin resistant E. faecium (VREfm). The aim of the present study was to investigate the prevalence of optrA gene among linezolid resistant E. faecium (LREfm) and to study the molecular epidemiology using pulse field gel electrophoresis (PFGE). Clinically significant LREfm were identified and antimicrobial susceptibility was performed by disc diffusion. Minimum inhibitory concentration (MIC) of linezolid, vancomycin, daptomycin and quinupristin/dalfopristin was determined by E-test. PCR and PCR-RFPL were performed for the detection of optrA/cfr gene and G2576T mutation respectively. Molecular epidemiology was studied by PFGE. A total of 1081 clinically significant Enterococci species were isolated which included E. faecium 63.5% (n=687) and E. faecalis 36.5% (n=394). LREfm (30/687) were further studied. Multidrug resistance and vancomycin resistance was 100% and 80%, respectively. Linezolid MIC range was 8-256µg/ml and the most common mechanism of resistance was optrA gene (83.3%) followed by G2576T mutation (33.3%). PFGE analysis demonstrated 4 major clones. The optrA gene mediated linezolid resistance was high and PFGE suggests resistance was emerging in the different background strains irrespective of resistance mechanism. Studies are required to investigate factors driving the emergence of linezolid resistance. The review suggests that this is the first report of optrA-mediated resistance in E. faecium from India.
Insights
The optrA gene is a major cause of linezolid resistance in Enterococcus faecium, a common hospital-acquired infection. This study highlights the high prevalence of optrA-mediated resistance in India, necessitating further investigation into its emergence.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Enterococcus faecium is a leading cause of nosocomial infections.
- Vancomycin-resistant E. faecium (VREfm) necessitates alternative treatments like linezolid (LNZ).
- Understanding linezolid resistance mechanisms is crucial for effective treatment strategies.
Purpose of the Study:
- To determine the prevalence of the optrA gene in linezolid-resistant E. faecium (LREfm).
- To investigate the molecular epidemiology of LREfm using pulse field gel electrophoresis (PFGE).
- To identify resistance mechanisms in LREfm.
Main Methods:
- Isolation and identification of clinically significant Enterococci species.
- Antimicrobial susceptibility testing and Minimum Inhibitory Concentration (MIC) determination for LNZ, vancomycin, daptomycin, and quinupristin/dalfopristin.
- Polymerase Chain Reaction (PCR) for optrA/cfr gene detection and PCR-RFLP for G2576T mutation analysis.
- Molecular typing using PFGE.
Main Results:
- Out of 1081 Enterococci isolates, 687 were E. faecium. Thirty LREfm isolates were identified.
- All LREfm isolates exhibited multidrug resistance; 80% were vancomycin-resistant.
- The optrA gene was the predominant resistance mechanism (83.3%), followed by G2576T mutation (33.3%).
- PFGE analysis revealed four distinct major clones of LREfm.
Conclusions:
- The optrA gene is a significant driver of linezolid resistance in E. faecium in India.
- Emergence of linezolid resistance appears to occur across diverse genetic backgrounds.
- Further research is needed to understand the factors contributing to the rise of linezolid resistance.
