Investigation Of The Pathogenicity Of Vibrio Alginolyticus Strains Isolated From Processed Hake And Seawater In Namibia And Validation Of Hydrogen Peroxide (H2o2) For The Disinfection Of Seaw

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.