Abstract

Ada River is an important freshwater resource whose microbiological quality may be influenced by human activities and environmental contamination. Assessing bacterial loads and the characteristics of resident bacteria is therefore essential for evaluating potential public-health risks. This study assessed bacterial abundance, diversity, and phenotypic virulence characteristics along different sections of the river using samples collected from upstream, midstream, and downstream locations during two sampling visits. Heterotrophic plate counts (HPC) were highest at the midstream section (145.00 ± 13.23 CFU/mL), followed by downstream (95.00 ± 22.64 CFU/mL) and upstream (46.88 ± 16.25 CFU/mL). Sampling location significantly influenced HPC [F (2,6) = 14.01, p = 0.01], whereas visitation and the interaction effect were not significant. Total coliform counts varied between 20.0 and 47.5 CFU/mL, but neither sampling location nor visitation significantly affected the counts. Sixty bacterial isolates representing seven genera were identified, with Pseudomonas spp. predominating overall (45.00%), followed by Bacillus spp. (28.33%) and Proteus spp. (13.33%). Bacterial distribution differed significantly across river sections (χ² = 24.15, p = 0.02). Phenotypic screening revealed biofilm formation in 40.00% of isolates, while protease, lipase, and cellulase production occurred in 40.00%, 36.67%, and 28.33%, respectively. β-haemolysis occurred in 26.67%, whereas γ-haemolysis predominated (73.33%). However, none of the virulence-associated characteristics varied significantly by sampling location. These findings indicate that Ada River harbours diverse bacteria with virulence-associated traits, highlighting potential environmental and public-health concerns and the need for regular water-quality monitoring and protection.