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

2001 ◽  
Vol 64 (1) ◽  
pp. 72-80 ◽  
Author(s):  
YUHUAN CHEN ◽  
KRISTIN M. JACKSON ◽  
FABIOLA P. CHEA ◽  
DONALD W. SCHAFFNER
Keyword(s):  
Food Service ◽  
Enterobacter Aerogenes ◽  
Scientific Basis ◽  
Food Preparation ◽  
Contamination Rate ◽  
Cross Contamination ◽  
Transfer Rates ◽  
Washing Efficiency ◽  
The Cross ◽  
Contamination Events

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.

Adequate Hand Washing and Glove Use Are Necessary To Reduce Cross-Contamination from Hands with High Bacterial Loads

2016 ◽  
Vol 79 (2) ◽  
pp. 304-308 ◽  
Author(s):  
ANDREW L. ROBINSON ◽  
HYUN JUNG LEE ◽  
JUNEHEE KWON ◽  
EWEN TODD ◽  
FERNANDO PEREZ RODRIGUEZ ◽  
...  
Keyword(s):  
Food Service ◽  
Enterobacter Aerogenes ◽  
Hand Washing ◽  
Cross Contamination ◽  
Bacterial Reduction ◽  
Bacterial Counts ◽  
Transfer Rates ◽  
Service Setting ◽  
Service Environments

ABSTRACT Hand washing and glove use are the main methods for reducing bacterial cross-contamination from hands to ready-to-eat food in a food service setting. However, bacterial transfer from hands to gloves is poorly understood, as is the effect of different durations of soap rubbing on bacterial reduction. To assess bacterial transfer from hands to gloves and to compare bacterial transfer rates to food after different soap washing times and glove use, participants' hands were artificially contaminated with Enterobacter aerogenes B199A at ~9 log CFU. Different soap rubbing times (0, 3, and 20 s), glove use, and tomato dicing activities followed. The bacterial counts in diced tomatoes and on participants' hands and gloves were then analyzed. Different soap rubbing times did not significantly change the amount of bacteria recovered from participants' hands. Dicing tomatoes with bare hands after 20 s of soap rubbing transferred significantly less bacteria (P < 0.01) to tomatoes than did dicing with bare hands after 0 s of soap rubbing. Wearing gloves while dicing greatly reduced the incidence of contaminated tomato samples compared with dicing with bare hands. Increasing soap washing time decreased the incidence of bacteria recovered from outside glove surfaces (P < 0.05). These results highlight that both glove use and adequate hand washing are necessary to reduce bacterial cross-contamination in food service environments.

Quantifying Bacterial Cross-Contamination Rates between Fresh-Cut Produce and Hands

2017 ◽  
Vol 80 (2) ◽  
pp. 213-219 ◽  
Author(s):  
Dane A. Jensen ◽  
Michelle D. Danyluk ◽  
Linda J. Harris ◽  
Donald W. Schaffner
Keyword(s):  
Bacterial Species ◽  
Enterobacter Aerogenes ◽  
Escherichia Coli O157 ◽  
Cross Contamination ◽  
Transfer Rates ◽  
E Coli ◽  
Significant Difference ◽  
Fresh Cut ◽  
Food Safety Risk ◽  
Risk Assessment And Management

ABSTRACT This study quantifies the cross-contamination rates between fresh-cut produce and hands using a nalidixic acid–resistant nonpathogenic Enterobacter aerogenes and cocktails of rifampin-resistant Salmonella or Escherichia coli O157:H7 strains. Volunteers performed the E. aerogenes experiments (n = 20), and one of the authors performed the Salmonella and E. coli O157:H7 experiments multiple times (n =15 and n =10, respectively). Each participant handled 25 g of fresh-cut carrots, celery, or cantaloupe in two different scenarios. In the first scenario, gloved hands were inoculated with 6 log CFU per hand of the bacteria, and in the second scenario, five 25-g pieces of fresh produce were inoculated to a concentration of 6 log CFU/25 g. The glove juice method was used to quantify the bacterial concentration on the gloved hands. About 30% of E. aerogenes on gloved hands was transferred to the carrots and celery, and 18% of E. aerogenes on gloved hands was transferred to the cantaloupe. When carrots or cantaloupe was inoculated with E. aerogenes, 1% was transferred to gloved hands; from inoculated celery, about 0.3% of E. aerogenes was transferred to gloved hands. There was not a significant difference between E. aerogenes and Salmonella cross-contamination rates (P > 0.05). When gloved hands were contaminated with E. coli O157:H7, about 30% was transferred to carrots, about 10% to celery, and about 3% to cantaloupe. When carrots and celery were inoculated with E. coli O157:H7, about 1% was transferred to gloved hands, but from inoculated cantaloupe only about 0.3% was transferred. Direction of transfer (to versus from produce), difference in type of produce, and differences among the bacterial species all had significant effects on the transfer rate. Understanding transfer rates to and from fresh-cut produce will allow for better risk assessment and management of microbial food safety risk related to fresh-cut produce.

Glove Barriers to Bacterial Cross-Contamination between Hands to Food

2001 ◽  
Vol 64 (6) ◽  
pp. 845-849 ◽  
Author(s):  
REBECCA MONTVILLE ◽  
YUHUAN CHEN ◽  
DONALD W. SCHAFFNER
Keyword(s):  
Nalidixic Acid ◽  
Transfer Rate ◽  
Microbial Contamination ◽  
Enterobacter Aerogenes ◽  
Published Data ◽  
Cross Contamination ◽  
Transfer Rates ◽  
Transfer Data ◽  
High Inoculum ◽  
Bare Hand

Human hands are an important source of microbial contamination of foods. However, published data on the effectiveness of handwashing and glove use in a foodservice setting are limited. Bacterial transfer through foodservice quality gloves was quantified using nalidixic acid-resistant Enterobacter aerogenes (a nonpathogenic surrogate with attachment characteristics similar to Salmonella). Five transfer rates were determined: chicken to bare hand, chicken to hand through gloves, bare hand to lettuce, hand to lettuce through gloves (with low inoculum on hands), and hand to lettuce through gloves (with high inoculum on hands). At least 30 observations were made for each percent transfer rate using 30 individual volunteers. The logarithm of percent transfer data were then fit to distributions: chicken to bare hand, normal (0.71, 0.42); chicken to hand through gloves, gamma (5.91, 0.40, −5.00); bare hand to lettuce, logistic (1.16, 0.30); hand to lettuce through gloves (low inoculum), normal (0.35, 0.88); hand to lettuce through gloves (high inoculum), normal (−2.52, 0.61). A 0.01% transfer was observed from food to hands and from hands to food when subjects wore gloves and a 10% transfer was observed without a glove barrier. These results indicate that gloves are permeable to bacteria although transfer from hands to food through a glove barrier was less than without a glove barrier. Our results indicate that gloves may reduce both bacterial transfer from food to the hands of foodservice workers and in subsequent transfer from hands back to food.

A Method of Assessing the Efficacy of Hand Sanitizers: Use of Real Soil Encountered in the Food Service Industry

2000 ◽  
Vol 63 (4) ◽  
pp. 495-501 ◽  
Author(s):  
D. L. CHARBONNEAU ◽  
J. M. PONTE ◽  
B. A. KOCHANOWSKI
Keyword(s):  
Service Industry ◽  
Food Service ◽  
Foodborne Illness ◽  
Food Preparation ◽  
Cross Contamination ◽  
Fresh Meat ◽  
Hand Sanitizer ◽  
Care Worker ◽  
Food Workers ◽  
Dose Dependent

In many outbreaks of foodborne illness, the food worker has been implicated as the source of the infection. To decrease the likelihood of cross-contamination, food workers must clean and disinfect their hands frequently. To ensure their effectiveness, hand disinfectants should be tested using rigorous conditions that mimic normal use. Currently, several different methods are used to assess the efficacy of hand disinfectants. However, most of these methods were designed with the health care worker in mind and do not model the specific contamination situations encountered by the food worker. To fill this void, we developed a model that uses soil from fresh meat and a means of quantifying bacteria that is encountered and transferred during food preparation activities. Results of studies using various doses of para-chloro-meta-xylenol and triclosan confirm that the method is reproducible and predictable in measuring the efficacy of sanitizers. Consistent, dose-dependent results were obtained with relatively few subjects. Other studies showed that washing hands with a mild soap and water for 20 s was more effective than applying a 70% alcohol hand sanitizer.

scholarly journals Inoculum Size Influences Bacterial Cross Contamination between Surfaces

2003 ◽  
Vol 69 (12) ◽  
pp. 7188-7193 ◽  
Author(s):  
R. Montville ◽  
D. W. Schaffner
Keyword(s):  
Transfer Rate ◽  
Linear Trend ◽  
Bacterial Species ◽  
Inoculum Size ◽  
Contamination Rate ◽  
Source Surface ◽  
Cross Contamination ◽  
Inoculum Level ◽  
Transfer Rates ◽  
Initial Inoculum

ABSTRACT Many factors have been shown to influence bacterial transfer between surfaces, including surface type, bacterial species, moisture level, pressure, and friction, but the effect of inoculum size on bacterial transfer has not yet been established. Bacterial cross contamination rates during performance of common food service tasks were previously determined in our laboratory using nalidixic acid-resistant Enterobacter aerogenes. Eight different transfer rates were determined, each involving a minimum of 30 volunteers. The influence of source inoculum level on the percentage of bacteria transferred (percent transfer rates) and log10 CFU per recipient surface was determined using statistical analysis. The effect of inoculum size on transfer rate was highly statistically significant (P< 0.0001) for all transfer rate data combined (352 observations) and for each individual cross contamination rate, except for data on contamination via transfer from chicken to hand through a glove barrier (P = 0.1643). Where inoculum size on the source was greater, transfer rates were lower, and where inoculum size on the source was less, transfer rates were higher. The negative linear trend was more obvious for activities that had a larger range of inoculum sizes on the source surface. This phenomenon has serious implications for research seeking to determine bacterial cross contamination rates, since the different transfer efficiencies that were previously shown to be associated with certain activities may actually be the result of differing initial inoculum levels. The initial inoculum size on the source and the amount of bacteria transferred must both be considered to accurately determine bacterial transfer rates.

scholarly journals Longer Contact Times Increase Cross-Contamination of Enterobacter aerogenes from Surfaces to Food

2016 ◽  
Vol 82 (21) ◽  
pp. 6490-6496 ◽  
Author(s):  
Robyn C. Miranda ◽  
Donald W. Schaffner
Keyword(s):  
Stainless Steel ◽  
Contact Time ◽  
Enterobacter Aerogenes ◽  
Food Type ◽  
Contamination Rate ◽  
Cross Contamination ◽  
Surface Type ◽  
Preparation Methods ◽  
Content Type ◽  
Interaction Terms

ABSTRACTBacterial cross-contamination from surfaces to food can contribute to foodborne disease. The cross-contamination rate ofEnterobacter aerogeneson household surfaces was evaluated by using scenarios that differed by surface type, food type, contact time (<1, 5, 30, and 300 s), and inoculum matrix (tryptic soy broth or peptone buffer). The surfaces used were stainless steel, tile, wood, and carpet. The food types were watermelon, bread, bread with butter, and gummy candy. Surfaces (25 cm2) were spot inoculated with 1 ml of inoculum and allowed to dry for 5 h, yielding an approximate concentration of 107CFU/surface. Foods (with a 16-cm2contact area) were dropped onto the surfaces from a height of 12.5 cm and left to rest as appropriate. Posttransfer, surfaces and foods were placed in sterile filter bags and homogenized or massaged, diluted, and plated on tryptic soy agar. The transfer rate was quantified as the log percent transfer from the surface to the food. Contact time, food, and surface type all had highly significant effects (P< 0.000001) on the log percent transfer of bacteria. The inoculum matrix (tryptic soy broth or peptone buffer) also had a significant effect on transfer (P= 0.013), and most interaction terms were significant. More bacteria transferred to watermelon (∼0.2 to 97%) than to any other food, while the least bacteria transferred to gummy candy (∼0.1 to 62%). Transfer of bacteria to bread (∼0.02 to 94%) was similar to transfer of bacteria to bread with butter (∼0.02 to 82%), and these transfer rates under a given set of conditions were more variable than with watermelon and gummy candy.IMPORTANCEThe popular notion of the “five-second rule” is that food dropped on the floor and left there for <5 s is “safe” because bacteria need time to transfer. The rule has been explored by a single study in the published literature and on at least two television shows. Results from two academic laboratories have been shared through press releases but remain unpublished. We explored this topic by using four different surfaces (stainless steel, ceramic tile, wood, and carpet), four different foods (watermelon, bread, bread with butter, and gummy candy), four different contact times (<1, 5, 30, and 300 s), and two bacterial preparation methods. Although we found that longer contact times result in more transfer, we also found that other factors, including the nature of the food and the surface, are of equal or greater importance. Some transfer takes place “instantaneously,” at times of <1 s, disproving the five-second rule.

Quantification of cross-contamination of Campylobacter jejuni during food preparation in a model kitchen in China

2020 ◽  
Author(s):  
Yao Bai ◽  
Xiao-Hui Lin ◽  
Jiang-Hui Zhu ◽  
Sheng-Hui Cui ◽  
Li-Xia Guo ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Cold Water ◽  
Scientific Evidence ◽  
Hot Water ◽  
Cross Contamination ◽  
Case Control Studies ◽  
Food Handling ◽  
Transfer Rates ◽  
The Cross ◽  
Cutting Boards

Numerous outbreak investigations and case-control studies of campylobacteriosis have provided evidence that handling Campylobacter -contaminated chicken products is a high risk factor for infection and illness. In this study, the cross-contamination and transfer rates of Campylobacter jejuni from chicken to ready-to-eat foods were determined in various food-handling scenarios. Skinless raw chicken breasts were artificially contaminated with Campylobacter jejuni and diced on three kinds of texture cutting boards. Whether cold water or cold water with detergent or hot water was used, statistically significant differences were found between the transfer rate of Campylobacter jejuni to unwashed and washed cutting boards or hands, respectively. When both kitchen knife and cutting board were reused after dicing the artificially contaminated chicken, the transfer rates of Campylobacter jejuni to cucumber cut on bamboo, wooden and plastic cutting board were 16.28%, 12.82% and 5.32%, respectively. The transfer rates from chicken to bread, a large lift-up water faucet handle and a small twist faucet handle via unwashed hands were 0.49%, 4.64% and 3.14%, respectively. This research provides scientific evidence that various types of contaminated kitchen-ware and cook’s hand are vital potential vehicles for the cross-contamination of Campylobacter from raw chicken to ready-to-eat food, and emphasizes the importance of timely and properly cleaning to prevent cross-contamination during food handling, therefore a high quality consumer education to reduce the risk of foodborne infection is urgent and necessary.

scholarly journals Simulating Cross-Contamination of Cooked Pork with Salmonella enterica from Raw Pork through Home Kitchen Preparation in Vietnam

2018 ◽  
Vol 15 (10) ◽  
pp. 2324 ◽  
Author(s):  
Sinh Dang-Xuan ◽  
Hung Nguyen-Viet ◽  
Phuc Pham-Duc ◽  
Delia Grace ◽  
Fred Unger ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Household Survey ◽  
Cross Contamination ◽  
Food Handling ◽  
Transfer Rates ◽  
Handling Practices ◽  
Food Handling Practices ◽  
Cutting Boards ◽  
Insight Into ◽  
Pork Consumption

Pork is the most commonly consumed meat in Vietnam, and Salmonella enterica is a common contaminant. This study aimed to assess potential S. enterica cross-contamination between raw and cooked pork in Vietnamese households. Different scenarios for cross-contamination were constructed based on a household survey of pork handling practices (416 households). Overall, 71% of people used the same knife and cutting board for both raw and cooked pork; however, all washed their hands and utensils between handling raw and cooked pork. The different scenarios were experimentally tested. First, S. enterica was inoculated on raw pork and surfaces (hands, knives and cutting boards); next, water used for washing and pork were sampled to identify the presence and concentration of S. enterica during different scenarios of food preparation. Bootstrapping techniques were applied to simulate transfer rates of S. enterica cross-contamination. No cross-contamination to cooked pork was observed in the scenario of using the same hands with new cutting boards and knives. The probability of re-contamination in the scenarios involving re-using the cutting board after washing was significantly higher compared to the scenarios which used a new cutting board. Stochastic simulation found a high risk of cross-contamination from raw to cooked pork when the same hands, knives and cutting boards were used for handling raw and cooked pork (78%); when the same cutting board but a different knife was used, cross-contamination was still high (67%). Cross-contamination between was not seen when different cutting boards and knives were used for cutting raw and cooked pork. This study provided an insight into cross-contamination of S. enterica, given common food handling practices in Vietnamese households and can be used for risk assessment of pork consumption.

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