Environmental isolation and in vitro characterisation of bacteriophages active against multidrug-resistant Acinetobacter baumannii.

Abstract

Background The increasing prevalence of antimicrobial resistance (AMR) has created an urgent need for alternative therapeutic strategies. Acinetobacter baumannii, a major cause of hospital-acquired infections, has been classified by the World Health Organization as a critical priority pathogen due to its high levels of multi-drug resistance. Bacteriophage therapy has re-emerged as a potential approach to combat infections caused by multidrug-resistant organisms. Methods Fifty multidrug-resistant (MDR) A. baumannii clinical isolates were collected. Bacteriophages were isolated from hospital sewage using standard enrichment protocols and screened for lytic activity against these isolates using spot and plaque assays. Morphological characterization of purified phages was performed using transmission electron microscopy. Results Three bacteriophages - vB_AbaS_SRNAIIMS002, vB_AbaS_SRNAIIMS008, and vB_AbaP_SRNAIIMS010 - were isolated and demonstrated lytic activity against MDR A. baumannii. Plaque assays revealed clear central zones with surrounding halos, indicating active bacterial lysis. Host range testing showed that two phages exhibited activity against multiple clinical isolates, whereas one displayed a narrow host range. Transmission electron microscopy revealed that two phages belonged to the family Siphoviridae, whereas one was morphologically consistent with the family Podoviridae. Conclusions This study reports the isolation and characterization of three bacteriophages active against MDR A. baumannii. These findings highlight the feasibility of isolating lytic phages from environmental sources and support further investigation of bacteriophage therapy as a complementary strategy to address infections caused by multidrug-resistant pathogens.