Abstract:
Most agricultural water sources are often considered contaminated, due to poorly
maintained sanitation systems, polluted river streams and other water catchment areas.
Agricultural water used for irrigation and reconstitution of pesticides is suspected to play
a direct or indirect role in the transmission of human pathogens to fresh produce. The
contamination of fresh table grapes during pesticide spraying can therefore be seen as
a potential risk factor. This study focuses on identifying possible sources and levels of
bacterial contamination in a river, holding dam and tank in table grape production areas.
In addition, the ability of selected pathogens to attach and survive on table grape
surfaces was studied using transmission electron microscopy. Water sources sampled
in this study were found to be microbiologically contaminated. Microbial populations
varied with season, sampling period within a season and water treatment conditions. No
human pathogens were detected under natural field conditions on crops irrigated with
contaminated water used for reconstituting agricultural pesticides. This study further
showed a wide range of pesticide products that permitted survival and multiplication of
most of the tested foodborne pathogens i.e. Escherichia coli 157:H7, Listeria
monocytogenes, Salmonella enterica subsp. enterica serovar Typhimurium and
Staphylococcus aureus. This information provides insight into the potential risk that may
be associated with table grapes due to the use of contaminated water. These findings
highlight the importance of considering pesticides used, water quality and spray
schedules prior to application. Detailed risk assessment studies on the potential of
contaminated irrigation water and the actual link with foodborne disease outbreaks have
not been investigated and should in future be determined as well as intervention
strategies.
