Characterisation of Lytic Bacteriophages Active Against Carbapenem-Resistant Acinetobacter baumannii Isolated from Wounds in Tertiary Hospitals in South West Nigeria

Carbapenem-resistant Acinetobacter baumannii is a critical priority pathogen responsible for intractable wound infections in Nigerian hospitals, and bacteriophage therapy offers a potential adjunct treatment strategy requiring systematic organism-specific characterisation. This study isolates and characterises lytic bacteriophages active against carbapenem-resistant Acinetobacter baumannii from wound infections at tertiary hospitals in Lagos and Ogun States, South West Nigeria. Clinical Acinetobacter baumannii isolates resistant to imipenem and meropenem were collected from wound swabs at LUTH and Olabisi Onabanjo University Teaching Hospital. Hospital wastewater and sewage served as phage sources. Phage isolation used double-layer agar overlay, and characterisation covered host range, one-step growth parameters, temperature and pH stability, and transmission electron microscopy. Whole genome sequencing was performed on five candidate phages. Six lytic phages were isolated with host ranges covering 60 to 85 percent of clinical isolates tested. Burst sizes ranged from 98 to 265 pfu/cell and latent periods from 12 to 20 minutes. All phages were stable between pH 5 and 9 and at temperatures up to 50 degrees Celsius. Genome analysis classified three phages in the Myoviridae family and two in Podoviridae. No lysogeny genes or antibiotic resistance genes were detected. The study provides characterised phage candidates for future pre-clinical phage therapy development against carbapenem-resistant A. baumannii in South West Nigerian hospitals. Keywords: bacteriophage, Acinetobacter baumannii, carbapenem resistance, wound infection, South West Nigeria