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

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.

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Determination of Free Chlorine Concentrations Needed To Prevent Escherichia coli O157:H7 Cross-Contamination during Fresh-Cut Produce Wash†

Journal of Food Protection ◽

10.4315/0362-028x.jfp-10-429 ◽

2011 ◽

Vol 74 (3) ◽

pp. 352-358 ◽

Cited By ~ 113

Author(s):

YAGUANG LUO ◽

XIANGWU NOU ◽

YANG YANG ◽

ISABEL ALEGRE ◽

ELLEN TURNER ◽

...

Keyword(s):

Escherichia Coli ◽

Free Chlorine ◽

Chlorine Concentration ◽

Wash Water ◽

Escherichia Coli O157 ◽

Cross Contamination ◽

E Coli ◽

Wash Solution ◽

Fresh Cut ◽

Experimental Trials

This study was conducted to investigate the effect of free chlorine concentrations in wash water on Escherichia coli O157:H7 reduction, survival, and transference during washing of fresh-cut lettuce. The effectiveness of rewashing for inactivation of E. coli O157:H7 on newly cross-contaminated produce previously washed with solutions containing an insufficient amount of chlorine also was assessed. Results indicate that solutions containing a minimum of 0.5 mg/liter free chlorine were effective for inactivating E. coli O157:H7 in suspension to below the detection level. However, the presence of 1 mg/liter free chlorine in the wash solution before washing was insufficient to prevent E. coli O157:H7 survival and transfer during washing because the introduction of cut lettuce to the wash system quickly depleted the free chlorine. Although no E. coli O157:H7 was detected in the wash solution containing 5 mg/liter free chlorine before washing a mix of inoculated and uninoculated lettuce, low numbers of E. coli O157:H7 cells were detected on uninoculated lettuce in four of the seven experimental trials. When the prewash free chlorine concentration was increased to 10 mg/liter or greater, no E. coli O157:H7 transfer was detected. Furthermore, although rewashing newly cross-contaminated lettuce in 50 mg/liter free chlorine for 30 s significantly reduced (P = 0.002) the E. coli O157:H7 populations, it failed to eliminate E. coli O157:H7 on lettuce. This finding suggests that rewashing is not an effective way to correct for process failure, and maintaining a sufficient free chlorine concentration in the wash solution is critical for preventing pathogen cross-contamination.

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Transfer efficacy of Escherichia coli O157:H7 between surfaces of green mature tomatoes and common food processing materials

Potravinarstvo Slovak Journal of Food Sciences ◽

10.5219/1408 ◽

2020 ◽

Vol 14 ◽

pp. 1027-1034

Author(s):

Oleksandr Tokarskyy ◽

Mykhaylo Korda ◽

Halyna Lukyantseva

Keyword(s):

Food Processing ◽

Risk Evaluation ◽

Conveyor Belt ◽

Post Inoculation ◽

Escherichia Coli O157 ◽

Cross Contamination ◽

Transfer Rates ◽

E Coli ◽

Common Food ◽

Special Concern

The objectives of this study were: a) to evaluate E. coli O157:H7 survival on green mature tomatoes and squares of common food processing materials – stainless steel, plastic (HDPE), and vinyl conveyor belt (PVC) – post-drying, stored at 25 ºC in the humidified environment for four days; b) to determine pathogen transfer rates (wet, 90 minutes, or 24-hours drying post-inoculation), from inoculated tomato surfaces to uninoculated steel, plastic, and vinyl conveyor belt squares and conversely. It was shown that E. coli O157:H7 did not survive well on the surface of tomatoes, resulting in a decline from 5.3 log10 CFU.mL-1 90 minutes post-drying to 1.4 log10 CFU.mL-1 on day 4. Similarly, the pathogen did not survive well on the surface of food processing squares, with numbers declining over 4 days from 4.04, 4.44, and 4.19 CFU.mL-1 of rinsate 90 minutes squares post-drying to 0.72, 0.50, 0.83 log10 CFU.mL-1, which is close to the detection limit, for the steel, vinyl belt, and plastic, respectively. Successful cross-contamination between tomatoes and food processing surfaces was achieved during wet transfer; while transfer after 90 minutes inoculum post-drying and 24 hours were less successful. This can be explained by both lack of liquid media with suspended bacteria for transfer and fast pathogen die-off after desiccation. Dry transfers, as shown by the percentage of “positive” for pathogen presence tomatoes and squares, as well as bacterial counts, were more successful from tomatoes to squares, but not conversely. Special concern raised vinyl conveyor belt, where the surface picked up the most pathogen cells from the surface of tomatoes, resulting in 100% positive during 90 minute-dry transfers, followed by plastic (66.7% positive) and steel (55.6% positive). To summarize, we presented data on the possibility of cross-contamination between mature green tomatoes and common food processing surfaces, which may be interesting for the processors for risk evaluation.

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Quantifying Transfer Rates of Salmonella and Escherichia coli O157:H7 between Fresh-Cut Produce and Common Kitchen Surfaces

Journal of Food Protection ◽

10.4315/0362-028x.jfp-13-098 ◽

2013 ◽

Vol 76 (9) ◽

pp. 1530-1538 ◽

Cited By ~ 37

Author(s):

DANE A. JENSEN ◽

LORETTA M. FRIEDRICH ◽

LINDA J. HARRIS ◽

MICHELLE D. DANYLUK ◽

DONALD W. SCHAFFNER

Keyword(s):

Escherichia Coli ◽

Disease Transmission ◽

Escherichia Coli O157 ◽

Cross Contamination ◽

Drying Time ◽

Transfer Rates ◽

Surface Moisture ◽

Food Contact ◽

Food Contact Surfaces ◽

Fresh Cut

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.

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Tracking an Escherichia coli O157:H7–Contaminated Batch of Leafy Greens through a Pilot-Scale Fresh-Cut Processing Line

Journal of Food Protection ◽

10.4315/0362-028x.jfp-14-058 ◽

2014 ◽

Vol 77 (9) ◽

pp. 1487-1494 ◽

Cited By ~ 11

Author(s):

ANNEMARIE L. BUCHHOLZ ◽

GORDON R. DAVIDSON ◽

BRADLEY P. MARKS ◽

EWEN C. D. TODD ◽

ELLIOT T. RYSER

Keyword(s):

Escherichia Coli ◽

Membrane Filtration ◽

Fluorescent Protein ◽

Pilot Scale ◽

Escherichia Coli O157 ◽

E Coli ◽

Leafy Greens ◽

Iceberg Lettuce ◽

Processing Line ◽

Fresh Cut

Cross-contamination of fresh-cut leafy greens with residual Escherichia coli O157:H7–contaminated product during commercial processing was likely a contributing factor in several recent multistate outbreaks. Consequently, radicchio was used as a visual marker to track the spread of the contaminated product to iceberg lettuce in a pilot-scale processing line that included a commercial shredder, step conveyor, flume tank, shaker table, and centrifugal dryer. Uninoculated iceberg lettuce (45 kg) was processed, followed by 9.1 kg of radicchio (dip inoculated to contain a four-strain, green fluorescent protein–labeled nontoxigenic E. coli O157:H7 cocktail at 106 CFU/g) and 907 kg (2,000 lb) of uninoculated iceberg lettuce. After collecting the lettuce and radicchio in about 40 bags (~22.7 kg per bag) along with water and equipment surface samples, all visible shreds of radicchio were retrieved from the bags of shredded product, the equipment, and the floor. E. coli O157:H7 populations were quantified in the lettuce, water, and equipment samples by direct plating with or without prior membrane filtration on Trypticase soy agar containing 0.6% yeast extract and 100 ppm of ampicillin. Based on triplicate experiments, the weight of radicchio in the shredded lettuce averaged 614.9 g (93.6%), 6.9 g (1.3%), 5.0 g (0.8%), and 2.8 g (0.5%) for bags 1 to 10, 11 to 20, 21 to 30, and 31 to 40, respectively, with mean E. coli O157:H7 populations of 1.7, 1.2, 1.1, and 1.1 log CFU/g in radicchio-free lettuce. After processing, more radicchio remained on the conveyor (9.8 g; P < 0.05), compared with the shredder (8.3 g), flume tank (3.5 g), and shaker table (0.1 g), with similar E. coli O157:H7 populations (P > 0.05) recovered from all equipment surfaces after processing. These findings clearly demonstrate both the potential for the continuous spread of contaminated lettuce to multiple batches of product during processing and the need for improved equipment designs that minimize the buildup of residual product during processing.

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

Journal of Food Protection ◽

10.4315/0362-028x-64.1.72 ◽

2001 ◽

Vol 64 (1) ◽

pp. 72-80 ◽

Cited By ~ 201

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.

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Fate of Escherichia coli O157:H7 and Other Coliforms in Commercial Mayonnaise and Refrigerated Salad Dressing

Journal of Food Protection ◽

10.4315/0362-028x-58.1.13 ◽

1995 ◽

Vol 58 (1) ◽

pp. 13-18 ◽

Cited By ~ 46

Author(s):

ERROL V. RAGHUBEER ◽

JIM S. KE ◽

MICHAEL L. CAMPBELL ◽

RICHARD S. MEYER

Keyword(s):

Escherichia Coli ◽

Storage Temperature ◽

Enterobacter Aerogenes ◽

Antimicrobial Effect ◽

Coliform Bacteria ◽

Escherichia Coli O157 ◽

Salad Dressing ◽

E Coli ◽

Survival Pattern ◽

High Level

Commercial mayonnaise and refrigerated ranch salad dressing were inoculated at two levels with two strains of Escherichia coli O157:H7, a non-pathogenic E. coli, and the non-fecal coliform Enterobacter aerogenes. Results showed that at the high inoculation level (>106 colony forming units [CFU]/g) in mayonnaise stored at room temperature (ca. 22°C) both strains of O157:H7 were undetected at 96 h. At the high inoculation level, all strains of coliform bacteria tested survived longer in salad dressing stored at 4°C than in mayonnaise stored at 22°C. The O157:H7 strains were still present at low levels after 17 days. The survival time in the low-level inoculum (104CFU/g) study decreased, but the survival pattern in the two products was similar to that observed in the high-level inoculum study. Slight differences in survival among strains were observed. The greater antimicrobial effect of mayonnaise may be attributable to differences in pH, water activity (aw), nutrients, storage temperature, and the presence of lysozyme in the whole eggs used in the production of commercial mayonnaise. Coliform bacteria survived longer in refrigerated salad dressing than in mayonnaise particularly at the high-level inoculum. Both mayonnaise (pH 3.91) and salad dressing (pH 4.51) did not support the growth of any of the microorganisms even though survival was observed.

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Antimicrobial Activity of Gaseous Allyl Isothiocyanate

Journal of Food Protection ◽

10.4315/0362-028x-60.8.943 ◽

1997 ◽

Vol 60 (8) ◽

pp. 943-947 ◽

Cited By ~ 86

Author(s):

PASCAL J. DELAQUIS ◽

PETER L. SHOLBERG

Keyword(s):

Bacterial Species ◽

Allyl Isothiocyanate ◽

Model System ◽

Penicillium Expansum ◽

Escherichia Coli O157 ◽

Fluorescent Pseudomonad ◽

Bacterial Cells ◽

E Coli ◽

Simple Model System ◽

Germination And Growth

A simple model system was constructed to evaluate the microbistatic and microbicidal properties of gaseous allyl isothiocyanate (AIT) against bacterial cells and fungal conidia deposited on agar surfaces. Salmonella typhimurium, Listeria monocytogenes Scott A, and Escherichia coli O157:H7 were inhibited when exposed to 1,000 μg AIT per liter. Pseudomonas corrugata, a Cytophaga species, and a fluorescent pseudomonad failed to grow in the presence of 500 μg AIT per liter. Germination and growth of Penicillium expansum, Aspergillus flavus, and Botrytis cinerea conidia was inhibited in the presence of 100 μg AIT per liter. Bactericidal and sporicidal activities varied with strain and increased with time of exposure, AIT concentration, and temperature. E. coli O157:H7 was the most resistant bacterial species tested.

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Prevalence of shiga toxin-producing Escherichia coli O157, O26 and O111 in milk, meat and faeces of cattle, sheep and pigs slaughtered in Benin

Journal of Applied Biosciences ◽

10.35759/jabs.152.6 ◽

2020 ◽

Vol 152 ◽

pp. 15667-15675

Author(s):

Chakirath Folakè Arikè Salifou ◽

Cyrille Boko ◽

Isidore Houaga ◽

Raoul Agossa ◽

Isabelle Ogbankotan ◽

...

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Virulence Genes ◽

Animal Origin ◽

Escherichia Coli O157 ◽

E Coli ◽

Milk Samples ◽

Food Of Animal Origin ◽

Cattle Faeces ◽

Risk Assessment And Management

Objectives: The study aimed to search for E. coli O157 and non-O157 in milk, meat and faeces of cattle, sheep and pigs slaughtered in Cotonou. Methodology and Results: One hundred and Seventy-Five (175) samples including 25 meat, 25 faeces per species and 25 milk from cattle were analysed for E. coli O157; O26 and O111 and the virulence genes were identified by PCR. The SAS software (1998) and the bilateral Z test were used to calculate and compare the identification frequencies. E. coli O157 was identified in 4% of cattle faeces, 4% of sheep faeces, and 20% of beef and, in 20% of milk samples. E. coli O26 was identified in 12% of cattle faeces and, in 8% of beef samples. E. coli O111 was identified at frequencies of 8%, and 12% in faeces of sheep and pigs, respectively. The eae gene was detected in 4% of beef, ovine meat, milk, pig faeces and in sheep faeces. stx1 was detected in 8% of milk, and in 4% of bovine and sheep faeces. The strains possessing the gene were all of E. coli O157 with the exception of one from pig faeces identified as O111. Conclusions and application of findings: The presence of these serogroups of E. coli with virulence genes poses a real food safety problem in Benin. This study findings must be taken into account for risk assessment and management related to the consumption of food of animal origin. Keywords: Benin, E. coli O157, O26, O111, faeces, meat, milk

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Simultaneous Enrichment of Shiga Toxin–Producing Escherichia coli O157 and O26 and Salmonella in Food Samples Using Universal Preenrichment Broth

Journal of Food Protection ◽

10.4315/0362-028x-72.10.2065 ◽

2009 ◽

Vol 72 (10) ◽

pp. 2065-2070 ◽

Cited By ~ 8

Author(s):

MASASHI KANKI ◽

KAZUKO SETO ◽

JUNKO SAKATA ◽

TETSUYA HARADA ◽

YUKO KUMEDA

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Food Samples ◽

Escherichia Coli O157 ◽

E Coli ◽

Significant Difference ◽

Peptone Water ◽

Radish Sprouts ◽

Pork Samples ◽

Better Than

Universal preenrichment broth (UPB) was compared with modified Escherichia coli broth with novobiocin (mEC+n) for enrichment of Shiga toxin–producing E. coli O157 and O26, and with buffered peptone water (BPW) for preenrichment of Salmonella enterica. Ten strains each of the three pathogens were inoculated into beef and radish sprouts following thermal, freezing, or no treatment. With regard to O157 and O26, UPB incubated at 42°C recovered significantly more cells from inoculated beef than UPB at 35°C and from radish sprout samples than UPB at 35°C and mEC+n. With regard to Salmonella, UPB incubated at 42°C was as effective as UPB at 35°C and BPW at recovering cells from beef and radish sprout samples. No significant difference was noted between the effectiveness of UPB at 42°C and UPB at 35°C or BPW in the recovery of Salmonella from 205 naturally contaminated poultry samples. By using UPB at 42°C, one O157:H7 strain was isolated from the mixed offal of 53 beef samples, 6 cattle offal samples, and 50 pork samples all contaminated naturally, with no pathogen inoculation. The present study found that UPB incubated at 42°C was as effective as, or better than, mEC+n for enrichment of O157 and O26 and comparable to BPW for preenrichment of Salmonella. These findings suggest that a great deal of labor, time, samples, and space may be saved if O157, O26, and Salmonella are enriched simultaneously with UPB at 42°C.

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