Microbiological safety and hygiene monitoring of coastal seawater at Northern public beaches of Mauritius and genetic characterization of human pathogenic Vibrio species

Northern public beaches are popular recreational and touristic destinations in Mauritius. However, rapid urbanization and coastal development in the region raise concerns about the microbial quality and safety of nearshore waters, which may deteriorate without effective surveillance and management. This could be exacerbated by the occurrence of marine, human pathogenic Vibrio, which may harbor genes conferring virulence and antimicrobial resistance. The aim of the study was thus to assess the microbiological safety and sanitary quality of Northern coastal seawater. The specific objectives were to (i) monitor the population of total Vibrio and hygiene indicator organisms over a ten-month period, and (ii) identify and genetically characterize any human pathogenic Vibrio isolates. Briefly, samples of seawater were collected at four public beaches (La Cuvette, Péreybère, Trou aux Biches and Mont Choisy) at different sampling points over a ten-month period (March - December) and subjected to microbiological and physicochemical analyses. Representative Vibrio isolates were subsequently analyzed by Whole Genome Sequencing for taxonomic identification and to reveal any virulence and antimicrobial resistance genes. Coliform counts varied significantly (P < 0.001) over the 10-month period. Mean coliform counts remained within the permissible limit (< 1000 CFU/100 ml) during most months, except for September and October. Vibrio counts were also higher during the period of September-December, compared to all other months. Three V. alginolyticus and one V. parahaemolyticus isolates were identified. V. parahaemolyticus ST 1498 was found to harbor genes imparting virulence (tdh + /trh+) and resistance to various antimicrobials (tetracycline, penicillin and β-lactam antibiotics). Findings of this exploratory study highlight the presence of human vibrios of suspected pathogenic potential, that warrants further investigation to understand their associated public health risks.