Characterisation of <i>Vibrio</i> Species from Surface and Drinking Water Sources and Assessment of Biocontrol Potentials of Their Bacteriophages

Abstract

The aim of this study was to characterise <i>Vibrio</i> species of water samples collected from taps, boreholes, and dams in the North West province, South Africa, and assess biocontrol potentials of their bacteriophages. Fifty-seven putative <i>Vibrio</i> isolates were obtained on thiosulfate-citrate-bile-salt-sucrose agar and identified using biochemical tests and species-specific PCRs. Isolates were further characterised based on the presence of virulence factors, susceptibility to eleven antibiotics, and biofilm formation potentials. Twenty-two (38.60%) isolates were confirmed as <i>Vibrio</i> species, comprising <i>V. harveyi</i> (45.5%, <i>n</i> = 10), <i>V. parahaemolyticus</i> (22.7%, <i>n</i> = 5), <i>V. cholerae</i> (13.6%, <i>n</i> = 3), <i>V. mimicus</i> (9.1%, <i>n</i> = 2), and <i>V. vulnificus</i> (9.1%, <i>n</i> = 2). Three of the six virulent genes screened were positively amplified; four <i>V. parahaemolyticus</i> possessed the <i>tdh</i> (18.18%) and <i>trh</i> (18.18%) genes, while the <i>zot</i> gene was harboured by 3 V. <i>cholerae</i> (13.64%) and one <i>V. mimicus</i> (4.55%) isolate. Isolates revealed high levels of resistance to cephalothin (95.45%), ampicillin (77.27%), and streptomycin (40.91%), while lower resistances (4.55%-27.27%) were recorded for other antimicrobials. Sixteen (72.7%) isolates displayed multiple antibiotic-resistant properties. Cluster analysis of antibiotic resistance revealed a closer relationship between <i>Vibrio</i> isolates from different sampling sites. The <i>Vibrio</i> species displayed biofilm formation potentials at 37°C (63.6, <i>n</i> = 14), 35°C (50%, <i>n</i> = 11), and 25°C (36.4%, <i>n</i> = 8). Two phages isolated in this study (vB_VpM_SA3V and vB_VcM_SA3V) were classified as belonging to the family Myoviridae based on electron microscopy. These were able to lyse multidrug-resistant <i>V. parahaemolyticus</i> and <i>V. cholerae</i> strains. These findings not only indicate the presence of antibiotic-resistant virulent <i>Vibrio</i> species from dam, borehole, and tap water samples that could pose a health risk to humans who either come in contact with or consume water but also present these lytic phages as alternative agents that can be exploited for biological control of these pathogenic strains.