Seasonal variability, antibiogram and genetic diversity of Vibrio spp. recovered from effluent discharge of wastewater treatment plants and their receiving rivers in Durban, South Africa.

Wastewater treatment plants (WWTPs) play a critical role in mitigating microbial contamination in aquatic environments. However, the persistence of pathogenic bacteria, including Vibrio spp., in treated effluents poses a significant public health risk. This study investigates the prevalence, seasonal variation, antibiotic resistance, and genetic diversity of Vibrio spp. in effluents from four WWTPs in Durban, South Africa and their receiving rivers. The removal efficiency of Vibrio spp. varied significantly across WWTPs, ranging from 76.41 to 100%, with biofilter-based systems, demonstrating the highest efficacy. Molecular identification confirmed Vibrio vulnificus and Vibrio alginolyticus as dominant species. Antibiotic susceptibility testing revealed widespread resistance, particularly to beta-lactams, with multidrug resistance (MDR) detected in 98% of isolates. The multiple antibiotic resistance index (MARI) values exceeded 0.2 in 99.5% of isolates, indicating significant antibiotic exposure. Genetic fingerprinting via repetitive extragenic palindromic PCR (REP-PCR) identified identical strains in effluent and downstream river samples, implicating treated effluent as a significant contamination source. These findings underscore the urgent need for improved wastewater treatment processes and stringent regulatory monitoring to mitigate the environmental and public health risks associated with antimicrobial-resistant Vibrio spp. Future research should focus on whole-genome sequencing to characterise resistance genes and assess the long-term impact of Vibrio contamination on aquatic ecosystems and human health.