Isolation and characterization of lytic bacteriophages against multi drug-resistant Acinetobacterbaumannii

The study aimed to isolate and identify bacteriophages specific to drug-resistant Acinetobacter baumannii from hospital sewage, while also characterizing the phenotypic and genotypic resistance mechanisms of the bacterial isolates, including efflux pump activity and biofilm formation. Notably, this research addresses a critical gap in the available literature, as no prior studies have reported the isolation and characterization of bacteriophages targeting A. baumannii in Bhopal or the broader Madhya Pradesh region (India). By exploring the therapeutic potential of bacteriophages in this underrepresented geographic area, this study contributes to the global understanding of phage therapy against multidrug-resistant (MDR) infections.

A. baumannii strains were isolated from hospital sewage and confirmed via PCR targeting the bla_OXA-51-like gene. Antibiotic susceptibility testing was performed to determine resistance profiles. Efflux pump activity, biofilm formation, and molecular resistance determinants were assessed. Lytic bacteriophages targeting MDR A. baumannii were isolated from sewage and characterized via TEM, RAPD-PCR, host range and bacterial reduction assay, one-step growth and stability analyses.

Four identified A. baumannii isolates exhibited MDR and extensively drug-resistant (XDR) profiles, with the coexistence of bla_OXA-23 and bla_NDM-1 genes. Efflux pump activity was detected in two isolates, and biofilm formation varied depending on sugar sources. Five bacteriophages were isolated, showing lytic activity against two MDR A. baumannii isolates. Phage Abp1 demonstrated strong bacterial reduction with a 30-min latent period and burst size of 68 PFU/cell with the highest titre at 37 °C and near neutral pH.

This study provides the first report of bacteriophage isolation and characterization against MDR A. baumannii in Bhopal, Madhya Pradesh (India), filling a significant research gap in this region. The findings highlight the potential of bacteriophages as therapeutic agents against MDR A. baumannii infections, particularly in hospital settings. By linking bacterial resistance traits with phage efficacy, this study reinforces the role of phage therapy as a promising alternative to conventional antibiotics.