Prevalence of Flesh-Eating Bacteria (Vibrio Vulnificus) Type A (Environmental) and Type B (Clinical) in Tilapia Fish Samples: Phenotypic and Molecular Characterizations.

Abstract

Vibrio vulnificus, both types A and B, in tilapia fish causes several diseases in humans-septicemia, gastroenteritis, and wound infection-that primarily occur due to the consumption of raw or undercooked fish. Using fresh tilapia fish samples collected from Riyadh market in Saudi Arabia, this study attempted to phenotypically detect V. vulnificus using specific media, such as thiosulphate citrate bile salt sucrose agar, CHROMagar™ Vibrio, and cellobiose polymyxin colistin agar, while Api 20NE was employed Molecular detection was conducted using 16S rRNA gene sequencing, to characterize the clinical (genotype B) and environmental strains (genotype A) of V. vulnificus. Virulence genes, such as hemolysin A (VvhA) and ViuB which encodes vulnibactin siderophores, were employed to detect both strains, in addition to capsular polysaccharide (CPS) and allele 1 genes. Virulence-correlated (vcg) genes vcgC and vcgE were also considered. The multidrug resistance of both strains to different antibiotics was tested, while whole-cell protein profiles were used to examine their differences based on Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis. The tilapia fish contained type A and B of V. vulnificus at a ratio of 12% and 4%, respectively. Generation times of the clinical and environmental strains were 14.45 min and 12.04 min, respectively. Analysis of the 16S rRNA, VvhA, CPS, ViuB, vcgC, and vcgE in type A and B revealed that both strains comprised all virulent genes in different ratios. Raw tilapia fish contained V. vulnificus type A and B, so care in handling is essential or during cooking these kinds of fish.