Quantification and variability analysis of bacterial cross-contamination rates in common food service tasks

J Food Prot. 2001 Jan;64(1):72-80. doi: 10.4315/0362-028x-64.1.72.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chickens
  • Colony Count, Microbial
  • Enterobacter aerogenes*
  • Evaluation Studies as Topic
  • Female
  • Food Contamination* / prevention & control
  • Food Handling*
  • Food Microbiology*
  • Hand / microbiology
  • Humans
  • Kinetics
  • Lettuce / microbiology
  • Male
  • Meat / microbiology
  • Risk Management
  • Statistical Distributions