Occurrence of Virulence Genes Associated with Human Pathogenic Vibrios Isolated from Two Commercial Dusky Kob (Argyrosmus japonicus) Farms and Kareiga Estuary in the Eastern Cape Province, South Africa.

Justine Fri,Anna Clarke,Roland Ndip,Henry Njom

doi:10.3390/ijerph14101111

Abstract

Background: Seafood-borne Vibrio infections, often linked to contaminated seafood and water, are of increasing global public health concern. The aim of this study was to evaluate the prevalence of human pathogenic vibrios and their associated virulence genes isolated from fish and water samples from 2 commercial dusky kob farms and Kareiga estuary, South Africa. Methods: A total of 200 samples including dusky kob fish (n = 120) and seawater (n = 80) were subjected to Vibrio screening on thiosulfate-citrate-bile salts-sucrose agar (TCBS). Presumptive isolates were confirmed and delineated to V. cholerae, V. parahaemolyticus, V. vulnificus, and V. fluvialis by PCR. Various pathogenic gene markers were screened: V. parahaemolyticus (trh and tdh), V. vulnificus (vcgE and vcgC) and V. fluvialis (stn, vfh, hupO, vfpA). Restriction Fragment Length Polymorphism (RFLP) of the vvhA gene of V. vulnificus strains was performed to determine the associated biotypes. Results: Total Vibrio prevalence was 59.4% (606/1020) of which V. fluvialis was the most predominant 193 (31.85%), followed by Vibrio vulnificus 74 (12.21%) and V. parahaemolyticus 33 (5.45%). No V. cholerae strain was detected. One of the V. parahaemolyticus strains possessed the trh gene 7 (9.46%) while most (91.9%; 68/74) V. vulnificus isolates were of the E-type genotype. V. fluvialis virulence genes detected were stn (13.5%), hupO (10.4%) and vfpA (1.0%). 12.16% (9/74) of V. vulnificus strains exhibited a biotype 3 RFLP pattern. Conclusions: This is the first report of potentially pathogenic vibrios from healthy marine fish in the study area, and therefore a public health concern.

Highlights

In recent years, there have been concerns about the microbiological safety of fish and other seafood due to increased outbreaks of seafood-borne pathogens
V. fluvialis virulence genes detected were stn (13.5%), heme utilization protein gene (hupO) (10.4%) and vfpA (1.0%). 12.16% (9/74) of V. vulnificus strains exhibited a biotype 3 Restriction Fragment Length Polymorphism (RFLP) pattern. This is the first report of potentially pathogenic vibrios from healthy marine fish in the study area, and a public health concern
Not all species of the genus are pathogenic to humans, incidences of human Vibrio-related illnesses over the last few years have been on the rise, in developing countries, with Vibrio cholerae, V. vulnificus, V. parahaemolyticus and V. fluvialis being the most important [2,3]

Summary

Introduction

There have been concerns about the microbiological safety of fish and other seafood due to increased outbreaks of seafood-borne pathogens. Members of the genus Vibrio are among the bacterial pathogens increasingly implicated in seafood-associated infections [1]. Not all species of the genus are pathogenic to humans, incidences of human Vibrio-related illnesses over the last few years have been on the rise, in developing countries, with Vibrio cholerae, V. vulnificus, V. parahaemolyticus and V. fluvialis being the most important [2,3]. Seafood-borne Vibrio infections, often linked to contaminated seafood and water, are of increasing global public health concern. The aim of this study was to evaluate the prevalence of human pathogenic vibrios and their associated virulence genes isolated from fish and water samples from 2 commercial dusky kob farms and Kareiga estuary, South Africa

Objectives

Methods

Results

Discussion

Conclusion