Detection of a New blaOXA-51-Like Variant (blaOXA-1328) and a Novel Sequence Type (ST3457/2790) in Acinetobacter baumannii Isolated from Community Sewage and an Incinerator Surface in Nigeria

Objective: Acinetobacter baumannii is an opportunistic pathogen with a high capacity to acquire antimicrobial resistance (AMR) determinants, including OXA-type β-lactamases, which confer carbapenem resistance. Environmental reservoirs play a crucial role in the persistence and spread of the bacteria, yet limited data exist on A. baumannii from non-hospital environments (which is critical in epidemiological studies) in Nigeria. This study aimed to study the genetic diversities of A. baumannii strains from different non-hospital environments in Nigeria, determine their sequence types (STs), and characterize their resistance genes. Results: While studying the prevalence of A. baumannii from 404 environmental samples (soil, sewage, water, and air) collected from three non-hospital communities in Nigeria, 2 isolates with novel features were discovered. Following culture-based and molecular identification, 33 isolates (7.5%) were confirmed as A. baumannii . Whole-genome sequencing (WGS) revealed the presence of one novel bla _OXA-51 -like variant ( bla _OXA1283 ) (that was diverged from bla _OXA-180 variants that were previously isolated from different environments in Nigeria) and one sequence type (ST3457/2790). A variant (bla _OXA-707 ) isolated from semi-pristine soil, is closely related to only one strain isolated from a stork bird in Poland. Another strain from an incinerator surface, clustered with strains from human oral sources in China, suggesting a potential link to clinical strains. The three isolates were susceptible to carbapenems (imipenem, meropenem), ceftazidime, tetracycline, gentamicin, sulfamethoxazole, and ciprofloxacin, suggesting minimal clinical exposure. However, a related strain carrying bla _OXA-120 from Egypt has been reported with additional bla _NDM-1 , a gene that mediates carbapenem resistance.