Prevalence and growth of pathogens on salad vegetables, fruits and sprouts.

A total of 120 samples, comprising different types of raw vegetables (seven), fruits (three) and sprouts (three) obtained from street vendors, were tested for aerobic plate count, coliform count and various food-borne pathogens. Average aerobic plate counts for salad vegetables, fruits and sprouts were greater than 10(10) cfu/g and 10(9) cfu/g respectively. Pathogens isolated were S. aureus, E. coli, Enterobacter sp., Klebsiella sp., S. typhi, Serratia sp., Providencia sp. and P. aeruginosa. The antibiotic resistant patterns of the isolates revealed P. aeruginosa to be the most antibiotic resistant, E. coli, Salmonella, Enterobacter and P. aeruginosa also showed the presence of plasmids. The model development phase of this study involved 27 growth curves conducted under 9 combinations of temperature and pH in the Brain Heart Infusion Broth. Models for specific growth rate and lag period were developed by response surface modelling using multiple linear regression analysis. The model provides an estimate of bacterial growth in response to any combination of the variables studied within specified ranges. Growth patterns of organisms on vegetable and fruits were also studied at room temperature (32 degrees C) to assess the growth in the actual food environment. Cucumber and watermelon supports the growth of S. aureus and S. typhi, carrot retarded their growth while pineapple did not support the growth.