title: Quantifying transfer rates of Salmonella and Escherichia coli O157:H7 between fresh-cut produce and common kitchen surfaces.
abstract: Cross-contamination between foods and surfaces in food processing environments and home kitchens may play a significant role in foodborne disease transmission. This study quantifies the cross-contamination rates between a variety of fresh-cut produce and common kitchen surfaces (ceramic, stainless steel, glass, and plastic) using scenarios that differ by cross-contamination direction, surface type, produce type, and drying time/moisture level. A five-strain cocktail of rifampin-resistant Salmonella was used in transfer scenarios involving celery, carrot, and watermelon, and a five-strain cocktail of rifampin-resistant Escherichia coli O157:H7 was used in transfer scenarios involving lettuce. Produce or surface coupons were placed in buffer-filled filter bags and homogenized or massaged, respectively, to recover cells. The resulting solutions were serially diluted in 0.1% peptone and surface plated onto tryptic soy agar with 80 μg/ml rifampin and bismuth sulfite agar with 80 μg/ml rifampin for Salmonella or sorbitol MacConkey agar with 80 μg/ml rifampin for E. coli O157:H7. When the food contact surface was freshly inoculated, a high amount (>90%) of the inoculum was almost always transferred to the cut produce item. If the inoculated food contact surfaces were allowed to dry for 1 h, median transfer was generally >90% for carrots and watermelon but ranged from <1 to ∼70% for celery and lettuce. Freshly inoculated celery or lettuce transferred more bacteria (<2 to ∼25% of the inoculum) compared with freshly inoculated carrots or watermelon (approximately <1 to 8%). After 1 h of drying, the rate of transfer from inoculated celery, carrot, and lettuce was <0.01 to ∼5% and <1 to ∼5% for watermelon. Surface moisture and direction of transfer have the greatest influence on microbial transfer rates.
authors.affiliation: Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901-8520, USA.
authors.forename: Dane A
authors.initials: DA
authors.lastname: Jensen
authors.forename: Loretta M
authors.initials: LM
authors.lastname: Friedrich
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Harris
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Danyluk
authors.forename: Donald W
authors.initials: DW
authors.lastname: Schaffner
mesh_terms: D015169:Colony Count, Microbial; D004866:Equipment Contamination; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005506:Food Contamination / Q000032:analysis* / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005638:Fruit / Q000382:microbiology; D018545:Lactuca / Q000382:microbiology; D010969:Plastics; D012475:Salmonella / Q000302:isolation & purification*; D013193:Stainless Steel; D014675:Vegetables / Q000382:microbiology
chemical_list: D010969:Plastics; D013193:Stainless Steel