Abstract:
The aim of this research is to determine the bacteriological quality of the irrigation
canal from Loskopdam, the two rivers that feed it and vegetables (broccoli and
cauliflower) in Mpumalanga, South Africa and also to predict the presence of selected
bacterial pathogens in irrigation water and on vegetables with logistic regression
analysis. Water and vegetable samples were examined for the presence of total
coliforms, faecal coliforms, Escherichia coli, Listeria monocytogenes, Salmonella sp.,
Enterococcus, Staphylococcus aureus, aerobic sporeformers, anaerobic sporeformers
and aerobic colony counts were done. Apart from bacterial analysis, the following
physico-chemical tests: temperature, pH, turbidity and COD were determined in water
samples. The average COD and turbidity in the two rivers and the canal were higher
than WHO and SA water guidelines. Sampling and analyses were done for a period of
12 months. Levels of faecal coliforms and E. coli were higher than the WHO
standard. S. aureus, Intestinal Enterococci, Salmonella, L. monocytogenes were
recovered from the two rivers and the canal. Apart from L. monocytogenes which was
not recovered from cauliflower, all bacterial pathogens recovered from the surface
water were recovered from the vegetables. Practical application: These results show that the rivers in Mpumalanga may
contribute to the contamination in the irrigation canal which may be a possible preharvest
source of contamination of broccoli and cauliflower, which may in turn
constitute a health risk to consumers. Logistic regression analysis of the sampled data
showed that COD was statistically reliable to predict L. monocytogenes, turbidity
reliable to predict Intestinal Enterococci and faecal coliform and coliform reliable to
predict Salmonella in irrigation water. Aerobic colony count (ACC) was statistically
significant for the prediction of the three pathogens in vegetables.
