Evaluation of Antibacterial Activity of Exogenous Glutathione and its Synergism with Meropenem against Clinical Isolates of Acinetobacter baumannii

Abstract

Introduction: Acinetobacter baumannii (A. baumannii) is the major nosocomial pathogen especially associated with ventilator associated pneumonia. It often poses significant challenge in treatment as it is resistant to almost all classes of antibiotics. Glutathione (GSH), a tripeptide antioxidant has been demonstrated with antibacterial activity in various bacteria. Aim: To detect the antibacterial activity of exogenous GSH against clinical isolates of A. baumannii and its synergism with meropenem. Materials and Methods: This prospective cross- sectional study was conducted at Department of Microbiology, Pondicherry Institute of Medical sciences, Puducherry, India. Sixty clinical isolates of A. baumannii from various clinical specimens between August to September 2018 were included in the study. The antibacterial activity of GSH at concentrations 10-20 mmol/L and meropenem were determined by broth dilution method. To determine the synergism, onto Muller Hinton Agar (MHA) with GSH (at Minimum Inhibitory Concentration (MIC)), Epsilometer (E) strips containing meropenem were placed over the lawn cultures. Fractional Inhibitory Concentration (FIC) of the isolates was also determined to demonstrate synergism of GSH with meropenem. The results were analysed by percentages and proportions. Results: Levels of MIC ranged from 16-18 mmol/L of exogenous GSH and >32 μg/mL for meropenem. The MIC of meropenem in the presence of GSH for all the isolates were <0.25 μg and the FIC <0.5, suggesting GSH synergistically interacts with meropenem. Conclusion: The GSH showed antibacterial activity against Acinetobacter baumannii and also acted synergistically with meropenem to reduce its MIC. Hence this study demonstrates the potential therapeutic utility of exogenous GSH against A. baumannii.