Prevalence, Distribution, and Diversity of Escherichia coli, Staphylococcus aureus, and Salmonella in Kiwifruit Orchards and Processing Plants

The aim of the study was to investigate the prevalence, distribution, and diversity of three foodborne bacteria in kiwifruit orchards and processing plants. Fourteen kiwifruit orchards and two processing plants in Shaanxi province were visited for sampling in 2012. Fruit samples and environmental samples in orchards and plants were taken for isolation of Escherichia coli, Staphylococcus aureus, and Salmonella. All isolates were characterized by antimicrobial susceptibility testing and detection of virulence genes. Selected isolates were further examined by pulsed-field gel electrophoresis (PFGE) analysis. In total, 160 E. coli isolates and 14 S. aureus isolates were recovered from 407 samples from orchards and plants, while no Salmonella was recovered. E. coli isolates displayed resistance most frequently to streptomycin (65.6%), and S. aureus isolates displayed resistance most frequently to erythromycin (21.4%). Three E. coli isolates (1.9%) were positive for stx2 and two S. aureus isolates (14.3%) were positive for both seb and seh. Seventy-seven E. coli isolates and 14 S. aureus isolates were analyzed by PFGE. PFGE results showed that both E. coli and S. aureus isolates were diverse, and blades for slicing during the processing could be an important contamination source. This study could provide useful information for kiwifruit growers and industry to establish proper management practices that help minimize the chance of microbial contamination from farm to table.