Prevalence of Antibiotic Resistant Bacteria from Imported and Local Fresh Produce

Imported fresh produce accounted for 44% of fresh vegetables and fruits consumption in U.S. in 2010. According to the Food and Drug Administration, the rise in fresh vegetables and fruits import upsurges the risks of foodborne illness. The main goal of this study was determine the prevalence of pathogenic bacteria in imported fresh produce in Nashville metropolitan area. A total of 360 imported and locally grown fresh vegetables and fruits samples was collected from three ethnic stores and three domestic stores and assessed for Salmonella, Shigella, E. coli O157:H7, and commensal bacteria. Selective media, agglutination and biochemical tests, and PCR were used for isolation and detection of Salmonella, Shigella, E. coli O157:H7 and other Enterobacteriaceae. The results showed that fresh produce from ethnic stores had higher Enterobacteriaceae contamination levels (7.99 log10 CFU/g) than produce from domestic produce (7.31 log10 CFU/g). Further results indicated that prevalence of Salmonella and Shigella in imported produce was significantly higher than that from local grown produce (1.0% vs. 0.0% and 3.1% vs. 1.7, respectively). Almost all sub-categories of commensal bacteria from ethnic stores were significantly higher than those from domestic stores. Leafy vegetables had the highest prevalence of commensal bacteria and the most prevalent commensal bacteria was Enterobacter spp. Enterobacteriaceae contamination levels in leafy vegetables, root vegetables, and tomato were 41.9%, 14.2%, 12.9%, respectively. Broccoli and bean sprouts had lowest prevalence of Enterobacteriaceae (1.9% and 1.9%, respectively) in all collected samples. An antimicrobial susceptibility test of the isolated bacteria was also carried out by the disk diffusion method. The data indicated that antibiotic-resistant Enterobacteriaceae was prevalent in fresh produce purchased from both imported and local produce. Antimicrobial resistant patterns of Enterobacteriaceae isolated from imported produce were different from those of the isolates from local grown produce in U.S. The highest Enterobacteriaceae resistance was indicated in vancomycin (100%), followed by erythromycin (91%), ampicillin (67%). None of the Enterobacteriaceae isolates were resistant to amikacin, gentamicin or ciprofloxacin. The higher temperature, poor sanitation and low fresh produce organization may contribute to the high prevalence of Enterobacteriaceae in ethnic stores. In reference to this study, fresh produce in ethnic stores have higher Enterobacteriaceae contamination levels than produce from domestic grocery stores. The data collected in this study will be invaluable for designing and developing information for consumer education and awareness of food safety issues as well as antimicrobial resistance in the food chain. The findings from this study suggest that antibiotic resistant foodborne pathogens may be associated with imported and local fresh produce, and warrant further large-scale studies