Occurrence of potentially pathogenic vibrios in final effluents of a wastewater treatment facility in a rural community of the Eastern Cape Province of South Africa
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Abstract
We assessed the occurrence of Vibrio pathogens in the final effluents of a rural wastewater
treatment facility in the Eastern Cape Province of South Africa as free or plankton-associated
(180 microm, 60 microm and 20 microm plankton sizes) entities using standard culture-based
and molecular techniques. The free-living Vibrio densities varied from 0 to 3.45 x
10(1) cfu ml(-1), while the plankton-associated Vibrio densities vary with plankton
sizes as follows: 180 microm (0-4.50 x 10(3) cfu ml(-1)); 60 microm (0-4.86 x 10(3)
cfu ml(-1)); 20 microm (0-1.9 x 10(5) cfu ml(-1)). The seasonal variations in the
Vibrio densities in the 180 and 60 microm plankton size samples were significant (p
< 0.05), while the 20 microm plankton size and free-living Vibrio densities were not.
Molecular confirmation of the presumptive vibrios isolates revealed fluvialis (36.5%),
as the predominant species, followed by Vibrio vulnificus (34.6%), and Vibrio parahaemolyticus
(23.1%); only API 20NE was employed to detect Vibrio metschnikovii (5.8%), suggesting
a high incidence of pathogenic Vibrio species in the final effluent of the rural wastewater
facility. Analysis suggested that the concentration of Vibrio species correlated negatively
with salinity and temperature (p < 0.001 and p < 0.002 respectively) as well as with
pH and turbidity (p < 0.001) in the final effluent. We conclude that rural wastewater
treatment facilities in the Eastern Cape Province of South Africa are potential sources
of Vibrio pathogens in the aquatic environment of the communities.