Quantification and Variability Analysis of Bacterial Cross-Contamination Rates in Common Food Service Tasks

Abstract

This study investigated bacterial transfer rates between hands and other common surfaces involved in food preparation in the kitchen. Nalidixic acid-resistant Enterobacter aerogenes B199A was used as a surrogate microorganism to follow the cross-contamination events. Samples from at least 30 different participants were collected to determine the statistical distribution of each cross-contamination rate and to quantify the natural variability associated with that rate. The transfer rates among hands, foods, and kitchen surfaces were highly variable, being as low as 0.0005% and as high as 100%. A normal distribution was used to describe the variability in the logarithm of the transfer rates. The mean +/- SD of the normal distributions were, in log percent transfer rate, chicken to hand (0.94 +/- 0.68), cutting board to lettuce (0.90 +/- 0.59), spigot to hand (0.36 +/- 0.90), hand to lettuce (-0.12 +/- 1.07), prewashed hand to postwashed hand (i.e., hand washing efficiency) (-0.20 +/- 1.42), and hand to spigot (-0.80 +/- 1.09). Quantifying the cross-contamination risk associated with various steps in the food preparation process can provide a scientific basis for risk management efforts in both home and food service kitchens.

Contamination of Fresh Produce by Microbial Indicators on Farms and in Packing Facilities: Elucidation of Environmental Routes

“…These two observations together suggest that hands are a reservoir of microorganisms and an important vehicle for their transfer to fresh produce during manual production, harvesting, and/or packing (32-34), common practices in produce production in this region (32). Though no other studies to date that we know of have quantified the relationships of microbes between hands and produce in the agricultural environment, this implication is consistent with those of other studies suggesting that hands are an important vehicle of contamination of produce (13,(33)(34)(35)(36). We hypothesize that microorganisms measured in our study could have been transferred either from hands to produce or produce to hands, as has been demonstrated to occur (33,(37)(38)(39).…”

Significance of Cross-contamination on Bacteriological Quality of Black Tiger Shrimp (Penaeus monodon Fabricius 1798) for Export Trade Produced in Fish Processing Plant

“…According to the World Health Organization [24], 25% of foodborne outbreaks are closely associated with cross-contamination events involving scarce hygiene practices, contaminated equipment, and contamination via food handlers, processing, or inadequate storage. Chen et al [25] demonstrated that bacterial transfer rates varied by more than five orders of magnitude depending on the nature of the surfaces involved in the cross-contamination. According to him a transfer rate of 100% was identified as the maximum value, although in some cases it was found that the recipients demonstrated higher numbers of microbial load than the contributor of contamination.…”

Background information on the current status of South African HIV/AIDS hospices in the context of hygiene and quality of life: A review

“…Several studies have indicated that various bacteria, including E. coli, S. aureus and Salmonella spp., can survive on human hands, sponges or cloths, utensils and currency for hours or days after initial contact (Scott and Bloomfield, 1990;Kusumaningrum et al, 2002). Other studies have quantified the extent of bacterial survival and cross-contamination between hands and various food items and kitchen surfaces (Zhaoet al, 1998;Chen et al, 2001;Montvilleet al, 2001). It became evident that quantifying the crosscontamination risk associated with various steps in the food preparation process can provide a scientific basis for risk management efforts in both the home and in food service.…”