Phenotypic detection of virulence attributes in MDR Acinetobacter from a tertiary care hospital, South India

• Author Details:   
• Monisha Basavaraju
• Rashmi P Mahale ^*
• M Raghavendra Rao
• Suchitra Shenoy

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Background: The nosocomial pathogen Acinetobacter baumannii is found all over the world and has a number of virulence characteristics that enable them to render resistance to antibiotics, making them multidrug resistant.

Objectives: To detect the virulence attributes of MDR Acinetobacter baumannii isolated from a tertiary care hospital in South India.

Materials and Methods: This prospective study, conducted from August 2023 to October 2024, involved 55 clinical and 55 environmental multidrug-resistant (MDR) Acinetobacter baumannii isolates. The isolates were evaluated for virulence factors using phenotypic assays, which included siderophore production assessed on Chrome Azurol S (CAS) agar, hemolytic activity on blood agar, proteolytic activity on milk agar, and biofilm formation using the tissue culture plate method.

Results: All clinical and environmental MDR A. baumannii isolates exhibited intermediate susceptibility to colistin. Tigecycline sensitivity was observed in 78% of the clinical isolates and 52.27% of the environmental isolates. Of the 55 clinical isolates of MDR A. baumannii, 34 (61.81%) showed biofilm production, 20 (36.36%) showed haemolytic activity, 29(52.72%) showed proteolytic activity and 30 (54.54%) showed siderophore production. Similarly, among the 55 Environmental isolates, 24 (43.63%) showed biofilm production, 15 (27.27%) showed haemolytic activity 31(56.36%) showed proteolytic activity and 19 (34.54%) showed siderophore production.

Conclusion: This study shows that the clinical MDR A. baumannii strains were more virulent than the environmental strains, thereby highlights its evolving virulence and resistance. This study also stresses the importance of continued surveillance, infection control practices and responsible antibiotic use in clinical setting.