Investigation of the Pathogenicity of Vobrio Alginolyticus strains isolated from processed hake and seawater in Namibia and validation of hydrogen peroxide (H2O2) for the disinfection of seawater
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Date
2015
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Abstract
In Namibia seawater is employed by marine fish factories during processing. Previous studies indicated that chlorine and Ultra Violet (UV) light are ineffective in keeping seawater free from bacteria throughout the distribution system. However, laboratory studies showed that hydrogen peroxide eliminates both sessile and attached bacteria from seawater. Secondly it is not known whether Vibrio alginolyticus bacteria isolated from the Namibian marine waters and from hake fish whose detection results into rejection of export products are pathogenic or not. This study was aimed at validating the ability of hydrogen peroxide (H2O2) to eliminate V. alginolyticus in seawater and to detect Vibrio species associated virulence factors in V. alginolyticus strains isolated from seawater and from hake fish products. Seawater used by factory B was dosed with 0.05% H2O2 and allowed to pass through pipes to collection points after which Vibrio counts in water and in fish products were determined. Secondly, V. alginolyticus strains isolated from seawater and hake fish and identified using 16S rRNA and rpoB genes were screened for toxR, tlh and tdh genes using PCR. V. parahaemolyticus LMG 2850 and V. alginolyticus Bcc892 were used as positive and negative controls respectively. High bacterial counts were detected from seawater treated with chlorine alone. Vibrio alginolyticus was detected in the fish processing factories were seawater was used and on fish products. Vibrio species were eliminated from seawater distribution system by 0.05% H2O2. Only one (1.9 %) out of 54 strains, tested tlh positive, but all the strains tested were toxR and tdh negative. This study, confirmed that these strains do not contain specific virulence genes known in other Vibrio species. Furthermore, this study confirmed that H2O2 is an effective disinfectant of seawater.
Description
A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science
Keywords
Pathogenicity, Vibrio alginolyticus strains, Hake, Seawater, Hydrogen peroxide