Development of a model for evaluation of microbial cross-contamination in the kitchen

Foods can become contaminated with pathogenic microorganisms from hands, the cutting board, and knives during preparation in the kitchen. A laboratory model was developed to determine occurrence of cross-contamination and efficacy of decontamination procedures in kitchen food-handling practices. Enterobacter aerogenes B199A, an indicator bacterium with attachment characteristics similar to that of Salmonella spp., was used. Chicken meat with skin inoculated with 10(6) CFU of E. aerogenes B199A/g was cut into small pieces on a sterile cutting board. The extent of cross-contamination occurring from meat to the cutting board and from the cutting board to vegetables (lettuce and cucumbers) subsequently cut on the board was determined. Swab samples from the cutting board, hand washings, and lettuce and cucumber samples revealed that approximately 10(5) CFU of E. aerogenes/cm(2) were transferred to the board and hands and approximately 10(3) to 10(4) CFU of E. aerogenes/g to the lettuce and cucumbers. The surfaces of the cutting board and hands were treated with antibacterial agents after cutting the meat, and counts of E. aerogenes on the cutting board and vegetables (lettuce and cucumbers) were determined. Results revealed that use of the disinfectant reduced the population of E. aerogenes to almost nondetectable levels on the cutting boards. The average counts after treatment were < 20 CFU/g of vegetable and ranged from < 20 to 200 CFU per cm(2) or g on the cutting board and subsequently on the vegetables. These results indicate that bacteria with attachment characteristics similar to Salmonella spp. can be readily transferred to cutting boards during food preparation and then cross-contaminate fresh vegetables if the boards are not cleaned. Application of a kitchen disinfectant can greatly reduce bacterial contamination on cutting boards.