Survival Of Foodborne Pathogens Research Articles

Survival of foodborne pathogens in unripe grape products

Antibacterial effects of unripe grape products (verjuice and sour grape sauce) which are particularly rich in antioxidants and organic acids were evaluated. Survival of Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium and Staphylococcus aureus which were inoculated in unripe grape products at different inoculum doses (2 and 6 log CFU/mL) was determined. All the samples were kept at room temperature (approximately 25 °C) for 0, 5, 15 and 30 min after inoculation with pathogens, separately. The unripe grape products which were inoculated at low inoculum dose inhibited all tested pathogens in 5 min, while it took 15 min for high inoculum dose. The pH, titratable acidity (tartaric acid %) and total sugar content values of the samples were between 2.14–2.74, 2.29–7.10% and 1.19–17.65 g/L, respectively. It was concluded that unripe grape products are microbiologically safe products and they have self-protection systems even when they were contaminated with pathogens at high levels.

Survival of foodborne pathogens in natural cracked olive brines

This work reports the survival (challenge tests) of foodborne pathogen species (Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella enterica) in Aloreña de Málaga table olive brines. The inhibitions were fit using a log-linear model with tail implemented in GInaFIT excel software. The olive brine had a considerable inhibitory effect on the pathogens. The residual (final) populations (Fp) after 24 h was below detection limit (<1.30 log10 cfu/mL) for all species assayed. The maximum death rate (kmax) was 9.98, 51.37, 38.35 and 53.01 h−1, while the time for 4 log10 reductions (4Dr) was 0.96, 0.36, 0.36 and 0.24 h for E. coli, S. aureus, L. monocytogenes and S. enterica, respectively. Brine dilutions increased Fp and 4Dr, while decreased kmax. A cluster analysis showed that E. coli had an overall quite different behaviour being the most resistant species, but the others bacteria behaved similarly, especially S. aureus and S. enterica. Partial Least Squares regression showed that the most influential phenols on microbial survival were EDA (dialdehydic form of decarboxymethyl elenolic acid), HyEDA (EDA linked to hydroxytyrosol), hydroxytyrosol 4-glucoside, tyrosol, and oleoside 11-methyl ester. Results confirm the adverse habitats of table olives for foodborne pathogenic microorganisms.

Physical and antimicrobial properties of anise oil loaded nanoemulsions on the survival of foodborne pathogens

The purpose of this research was to investigate antimicrobial effects of nano emulsions of anise oil (AO) on the survival of common food borne pathogens, Listeria monocytogenes and Escherichia coli O157:H7. Series of emulsions containing different level of anise oil as potential antimicrobial delivery systems were prepared. Antimicrobial activities of bulk anise oil and its emulsions (coarse and nano) was tested by the minimum inhibitory concentration and time kill assay. Our results showed that bulk anise oil reduced the population of E. coli O157:H7 and L. monocytogenes by 1.48 and 0.47logcfu/ml respectively after 6h of contact time. However, under the same condition anise oil nanoemulsion (AO75) reduced E. coli O157:H7 and L. monocytogenes count by 2.51 and 1.64logcfu/ml, respectively. Physicochemical and microbial analyses indicated that both nano and coarse emulsions of anise oil showed better and long-term physicochemical stability and antimicrobial activity compared to bulk anise oil.

Effect of sulfur dioxide fumigation on survival of foodborne pathogens on table grapes under standard storage temperature

We examined the fate of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica Thompson inoculated on freshly-harvested table grapes under standard cold storage with initial and weekly sulfur dioxide (SO2) fumigation. L. monocytogenes and S. enterica Thompson were much more sensitive to cold temperature than E. coli O157:H7. Furthermore, L. monocytogenes was highly susceptible to SO2. Initial fumigation with 100 or 200 ppm-hr was sufficient to eliminate this pathogen on grapes with low (104 cells/grape) and high (106 cells/grape) inocula, respectively. Initial fumigation with 300 ppm-hr reduced S. enterica Thompson population about 300- and 10-fold on grapes with low and high inocula, respectively. Initial fumigation with 300 ppm-hr reduced E. coli O157:H7 population to less than 10-fold, regardless of inoculum density. When grapes were inoculated with the high inoculum and fumigated on days 0 and 7 with 200 or 300 ppm-hr SO2, S. enterica Thompson and E. coli O157:H7 were completely inactivated between days 8 and 14 of cold storage. Standard cold storage combined with SO2 fumigation was effective in reducing and eliminating all three pathogens on table grapes, however, depending on the dose, two or three fumigations were needed for elimination of S. enterica Thompson and E. coli O157:H7.

Survival of Foodborne Pathogens on Berries

Fresh and frozen berries are popular foods. When berries are picked for fresh consumption, they are usually packed directly without washing because they are highly perishable. There is typically no “kill step” that would eliminate pathogens on fresh or frozen berries. Foodborne illness outbreaks have been associated with the consumption of fresh or frozen berries that were contaminated with pathogenic viruses, parasites, or bacteria. Contamination can occur before or during harvest or during final preparation. This 11-page fact sheet was written by Mary Palumbo, Linda J. Harris, and Michelle D. Danyluk, and published by the UF Department of Food Science and Human Nutrition, November 2013.

Effect of quantity of food residues on resistance to desiccation of food-related pathogens adhered to a stainless steel surface

In order to study the effect of food residues on the survival of food-borne pathogens, Salmonella Typhimurium, Staphylococcus aureus, and Listeria monocytogenes were subjected to drying conditions in the presence of small amounts of food such as carrot juice, aqueous solution of nori, milk, and soy-milk. After drying for 2 h at room temperature in the absence of food residue, cell counts of S. Typhimurium, S. aureus, and L. monocytogenes decreased from 8 to 3, 6, and 5 log cfu/dish, respectively. Five milligrams of fresh carrot, 0.05 mg dried nori, and 100 nL milk or soy milk per 10 mm φ surface were sufficient to demonstrate a protective effect on the adhered pathogens, as confirmed by atomic force microscopy. Results from this study suggest that small sediments of food, not only protein rich but also carbohydrate rich, increase the resistance of surface-adherent bacteria to desiccation, rendering sanitization processes ineffective and encouraging cross contamination.

Survival of foodborne pathogens on inshell walnuts

The survival of Salmonella enterica Enteritidis PT 30 or five-strain cocktails of S. enterica, Escherichia coli O157:H7, and Listeria monocytogenes was evaluated on inshell walnuts during storage. Inshell walnuts were separately inoculated with an aqueous preparation of the pathogens at levels of 10 to 4log CFU/nut, dried for 24h, and then stored at either 4°C or ambient conditions (23–25°C, 25–35% relative humidity) for 3weeks to more than 1year. During the initial 24-h drying period, bacterial levels declined by 0.7 to 2.4log CFU/nut. After the inoculum dried, further declines of approximately 0.1log CFU/nut per month of Salmonella Enteritidis PT 30 levels were observed on inshell walnuts stored at 4°C; at ambient conditions the rates of decline ranged from 0.55 to 2.5log CFU/nut per month. Rates of decline were generally greater during the first few weeks of storage, particularly at lower inoculum levels. The survival of the five-strain cocktails inoculated at very low levels (under 400CFU/nut) was determined during storage at ambient conditions. The pathogens could be recovered by either enumeration or enrichment from most samples throughout the 3-month storage period; reductions in bacterial levels from the beginning to end of storage were 0.7, 0.2, and 2.3log CFU/nut for Salmonella, E. coli O157:H7, and L. monocytogenes, respectively. For 6% of all nut samples (14 of 234 samples), pathogens were isolated from the second but not first 24-h enrichment, suggesting that bacterial cells were viable but not easily culturable. Salmonella-inoculated walnuts were exposed for 2min to water or a 3% solution of sodium hypochlorite (to mimic commercial brightening) either 24h or 7days after inoculation; treated nuts were dried for 24h and held at ambient conditions. Salmonella levels were reduced by less than 0.5log or 2.4 to 2.6log CFU/nut on water– or chlorine– treated walnuts, respectively, regardless of postinoculation treatment time. Additional reductions of 2.6 and 2.1log CFU/nut were observed for water- and chlorine-treated walnuts, respectively, after storage for 2weeks at ambient conditions. Bacterial foodborne pathogens are capable of long-term survival on the surface of inshell walnuts even when initial levels are low.

Survival of foodborne pathogens at different relative humidities and temperatures and the effect of sanitizers on apples with different surface conditions

We investigated the effects of factors such as relative humidity (RH) and temperature on pathogen survival on apples with different surface conditions. Apples with different surface conditions (unblemished, bruised, or cut) were inoculated with three pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, and Staphylococcus aureus) and stored at different RH levels (RH 100, 85, or 68%) at 4 °C or 15 °C for 2 days. S. aureus survived most readily on apple surfaces; it had no significant reduction on any of the apple surfaces for any of the three RH levels after 2 days of storage. The reduction levels of E. coli O157:H7 and S. Typhimurium on unblemished and bruised apple surfaces were higher at RH of 85% and 68% than at RH of 100% at 15 °C; and reduction levels were approximately 3 log10 CFU/apple at 4 °C in RH of 68%. No significant reduction in any of the three pathogens on cut apple surfaces was observed for any RH level. The effectiveness of chemical sanitizers (chlorine sanitizer and 2% lactic acid) in reducing pathogens (E. coli O157:H7, S. Typhimurium, and S. aureus) on apple surfaces (unblemished, bruised, or cut) was also evaluated. Treatment with chlorine sanitizer and 2% lactic acid for 5 min significantly reduced pathogen levels on unblemished and bruised apple surfaces but not on cut apple surfaces. In conclusion, the surface conditions of the apple significantly affected pathogen survival and the effectiveness of sanitizing methods.

Survival of food-borne pathogens on natural black table olives after post-processing contamination

The aim of this study was to evaluate the survival of Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus on natural black olives during aerobic storage without brine and to conclude about the safety of this fermented food. Fermented black olives (pH3.95; NaCl 6.02%) were artificially inoculated with 4 strains of Salmonella enterica ser. Enteritidis, 4 strains of S. enterica ser. Typhimurium, 3 strains of E. coli O157:H7, 3 strains of L. monocytogenes, and 3 strains of S. aureus either in monoculture or in mixed culture by submerging the fruits in a solution containing ca. 7.0logCFU/ml of each target pathogen. The olives were subsequently stored aerobically at 4 and 20°C, and the pathogens were recovered on selective media for a time period of 15days. Enrichment was employed to define the presence/absence of the target pathogens when their counts were below the detection limit of direct plating. Results showed that the population of all pathogens presented a rapid decline within the first 2days of storage depending on storage temperature, type of inoculation (monoculture or cocktail) and strain. Storage at 4°C seemed to prolong the survival of certain strains of pathogens as compared to 20°C by ca. 1day. Enrichment revealed the absence (<1CFU/25g) of Salmonella and E. coli O157:H7 from olive samples with the exception of all strains of L. monocytogenes at 4°C and one strain at 20°C that were detected by selective enrichment until the end of storage. The results of this study indicate that natural black olives are not a favorable environment to support the growth of the investigated pathogens after post-processing contamination provided that the olives have been subjected to proper fermentation process.

Effects of gallotannin treatment on attachment, growth, and survival of Escherichia coli O157:H7 and Listeria monocytogenes on spinach and lettuce

Food-borne illness outbreaks are increasingly associated with fresh produce. Their high prevalence may reflect the lack of methods to effectively remove pathogenic bacteria from the surface of fruits and vegetables. This study evaluated the effect of antimicrobial gallotannins on attachment, growth, and survival of food-borne pathogens on green leafy vegetables. Spinach leaves and interior leaves of lettuce harboring high and low cell counts of background microbiota, respectively, were washed with tap water with and without added gallotannins. To account for the variability among organisms, green leafy vegetables were inoculated with strain cocktails of Escherichia coli O157:H7 and Listeria monocytogenes. Cell counts of L. monocytogenes were significantly reduced by the gallotannin treatment. Lower cell counts after storage for 8 days at 4 °C demonstrated antimicrobial effects of gallotannins retained on the surface of green leafy vegetables. Gallotannin treatments with 1 g/L did not inhibit E. coli O157:H7 but hindered their attachment to filter paper by up to 94 %. The addition of gallotannin-containing extracts from mango (Mangifera indica L.) kernels to the washing water did neither alter color nor texture of bagged fresh-cut products. In conclusion, gallotannin treatment significantly reduced surface contamination of green leafy vegetables with L. monocytogenes and reduced the attachment of cells of E. coli O157:H7.

Resistance of pathogenic bacteria on the surface of stainless steel depending on attachment form and efficacy of chemical sanitizers

Various bacteria including food spoilage bacteria and pathogens can form biofilms on different food processing surfaces, leading to potential food contamination or spoilage. Therefore, the survival of foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, Cronobacter sakazakii) in different forms (adhered cells, biofilm producing in TSB, biofilm producing at RH 100%) on the surface of stainless steel and stored at various relative humidities (RH 23%, 43%, 68%, 85%, and 100%) at room temperature for 5 days was investigated in this study. Additionally, the efficacy of chemical sanitizers (chlorine-based and alcohol-based commercial sanitizers) on inhibiting various types of biofilms of E. coli O157:H7 and S. aureus on the surface of stainless steel was investigated. The number of pathogens on the surface of stainless steel in TSB stored at 25°C for 7 days or RH 100% at 25°C for 7 days was significantly increased and resulted in the increase of 3 log(10) CFU/coupon after 1 day, and these levels were maintained for 7 days. When stainless steel coupons were stored at 25°C for 5 days, the number of pathogens on the surface of stainless steel was significantly reduced after storage at RH 23%, 43%, 68%, and 85%, but not at 100%. When the bacteria formed biofilms on the surface of stainless steel in TSB after 6 days, the results were similar to those of the attached form. However, levels of S. aureus and C. sakazakii biofilms were more slowly reduced after storage at RH 23%, 43%, 68%, and 85% for 5 days than were those of the other pathogens. Formation of biofilms stored at RH 100% for 5 days displayed the highest levels of resistance to inactivation. Treatment with the alcohol sanitizer was very effective at inactivating attached pathogens or biofilms on the surface of stainless steel. Reduction levels of alcohol sanitizer treatment ranged from 1.91 to 4.77 log and from 4.35 to 5.35 log CFU/coupon in E. coli O157:H7 and S. aureus, respectively. From these results, the survival of pathogens contaminating the surfaces of food processing substrates such as stainless steel varied depending on RH and attachment form. Also, alcohol-based sanitizers can be used as a potential method to remove microbial contamination on the surfaces of utensils, cooking equipment, and other related substrates regardless of the microbial attached form.

Growth and survival of foodborne pathogens in beer.

This work aimed to assess the growth and survival of four foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus) in beer. The effects of ethanol, pH, and storage temperature were investigated for the gram-negative pathogens (E. coli O157:H7 and Salmonella Typhimurium), whereas the presence of hops ensured that the gram-positive pathogens (L. monocytogenes and S. aureus) were rapidly inactivated in alcohol-free beer. The pathogens E. coli O157:H7 and Salmonella Typhimurium could not grow in the mid-strength or full-strength beers, although they could survive for more than 30 days in the mid-strength beer when held at 4°C. These pathogens grew rapidly in the alcohol-free beer; however, growth was prevented when the pH of the alcohol-free beer was lowered from the "as received" value of 4.3 to 4.0. Pathogen survival in all beers was prolonged at lowered storage temperatures.

The growth and survival of food-borne pathogens in sweet and fermenting brewers' wort

The aim of this study was to investigate the factors affecting the survival and growth of four food-borne pathogens ( Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus) in sweet and fermenting brewery wort. The Gram-negative pathogens ( E. coli and Salm. Typhimurium) were capable of growth during the initial stages of fermentation in hopped wort, although they were quickly inactivated when added during the later stages of fermentation. When the wort was left unpitched, the two Gram-negative pathogens grew unabated. Pathogen growth and survival was enhanced as the pH was increased, and as both the ethanol and original gravity were decreased. Although having no effect on the Gram-negative pathogens, low levels of hop iso-α-acids were sufficient to inhibit L. monocytogenes, and a synergistic antimicrobial effect between iso-α-acids and pH was observed. S. aureus failed to initiate growth in all of the test worts. There appears to be no reason for concern of the safety of a “typical” wort during fermentation, however due attention should be paid when wort is stored or antimicrobial hurdles are lowered, for example in the production of reduced and alcohol-free beer, and in unpasteurised products.

Survival of Foodborne Pathogens in Grain Products and the Effect of Catechins

We investigated the survival of bacterial pathogens in grain products. Salmonella Enteritidis and Staphylococcus aureus survived for more than 3 weeks in grain flakes. Although S. Enteritidis in grain flakes reached a level of less than 10(2) CFU/g, the surviving organisms grew rapidly in milk and reached 10(9) CFU/g after 25-hr incubation. When catechins were present on the grain flakes, the numbers of S. Enteritidis and S. aureus were significantly decreased. In addition, catechins reduced the survival and growth of S. Enteritidis, S. aureus and Bacillus cereus when added to cooked grain products. This study indicates that S. Enteritidis, S. aureus and Bacillus can survive for a long time in grain products and that catechins impair their survival and growth.

In VivoExpression Technology and Signature-Tagged Mutagenesis Screens for Identifying Mechanisms of Survival of Zoonotic Foodborne Pathogens

High-throughput genetic screens provide great insights into the biochemistry and molecular biology of how bacteria sense, respond to, and propagate within their environments. Genomics era techniques such as microarrays and proteomics have great potential to increase our understanding of how foodborne pathogens grow and survive within animal and human hosts, in the environment and foods, and during thermal and nonthermal inactivation protocols. While these techniques are incredibly useful for studying gene expression in simplified in vitro conditions, it is much more challenging to pursue similar studies within more complex experimental models such as in vivo, within the food matrix, or within heterogeneous microbial populations. Techniques such as in vivo expression technology (IVET) and signature-tagged mutagenesis (STM) provide alternatives for studying bacterial gene expression and growth requirements within these settings. These techniques are used extensively by the medical, veterinary, and plant research communities for identifying genes promoting the colonization and disease process, factors mediating commensalism between bacteria and their host, and genes that promote survival of environmental bacteria within natural settings. Research into the transmission and survival of foodborne pathogens from farm-to-fork would likely benefit from these techniques, however there are few reports describing their use for such purposes. This review will briefly cover the methods of IVET and STM, discuss how these techniques improved our understanding of the interactions between zoonotic foodborne pathogens and their animal hosts, and ask whether these techniques could be further exploited to better understand the survival of foodborne pathogens within the environment, within food matrices, and during inactivation protocols.

Antimicrobial Activity of Olive Oil, Vinegar, and Various Beverages against Foodborne Pathogens

The survival of foodborne pathogens in aqueous extracts of olive oil, virgin olive oil, vinegar, and several beverages was evaluated. Vinegar and aqueous extracts of virgin olive oil showed the strongest bactericidal activity against all strains tested. Red and white wines also killed most strains after 5 min of contact, black and green tea extracts showed weak antimicrobial activity under these conditions, and no effect was observed for the remaining beverages (fruit juices, Coca-Cola, dairy products, coffee, and beer). The phenolic compound content of the aqueous olive oil and virgin olive oil extracts could explain their antibacterial activity, which was also confirmed in mayonnaises and salads used as food models. Virgin olive oil in mayonnaises and salads reduced the counts of inoculated Salmonella Enteritidis and Listeria monocytogenes by approximately 3 log CFU/g. Therefore, olive oil could be a hurdle component in certain processed foods and exert a protective effect against foodborne pathogens when contaminated foods are ingested.

Factors Affecting Compost Tea as a Potential Source of Escherichia coli and Salmonella on Fresh Produce

Compost tea (CT) is an unheated on-farm infusion of compost used as a spray or soil drench to promote plant growth and control foliar and root diseases. Because food safety involves all aspects from farm to fork, CT should meet basic microbiological criteria for water quality. This report describes the effects of two CT production processes, aerated and nonaerated, on growth and survival of foodborne pathogens and fecal coliforms. Seven commercially available nutrients used to supplement CT were tested individually and in combination for their effects on the growth of Escherichia coli and Salmonella. Compost containing 101 to 103 CFU/g initial concentrations of E. coli O157:H7 and Salmonella Enteritidis were used to assess growth and survival responses to aerated CT (36-h preparations) and nonaerated CT (8.5-day preparations). Pathogen and fecal coliform populations were undetectable by 8.5 days in nonaerated CT without nutrient supplements. E. coli O157:H7 decreased to below detection levels in aerated CT at 36 h without the use of supplements. In contrast, the addition of commercially formulated mixtures or combinations of nutrient supplements resulted in growth of E. coli O157: H7, Salmonella, and fecal coliforms by 1 to 4 log CFU/g in both aerated and nonaerated CT. When nutrient supplements were added, aerated CT sustained higher concentrations of E. coli O157:H7, Salmonella, and fecal coliforms than did nonaerated CT. Thus, addition of supplements supports growth of human pathogens from very low initial concentrations in both aerated and nonaerated CT and should be avoided when CT is used on fresh produce.

Radiation Sensitivity and Postirradiation Growth of Foodborne Pathogens on a Ready-to-Eat Frankfurter on a Roll Product in the Presence of Modified Atmosphere and Antimicrobials

Intervention technologies including ionizing radiation, antimicrobials, and modified atmospheres (MA) can be used to inhibit the growth of or inactivate foodborne pathogens on complex ready-to-eat foods such as sandwiches. However, the effect of these technologies when used in combination (the hurdle concept) on the survival of foodborne pathogens is unknown. The ability of ionizing radiation to inactivate Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, and Staphylococcus aureus inoculated onto a frankfurter on a roll product containing the antimicrobials sodium diacetate and potassium lactate in the presence of an MA (100% N2, 50% N2 plus 50% CO2, or 100% CO2) was investigated. The radiation resistances (D10-values) of the foodborne pathogens were 0.43 to 0.47 kGy for E. coli O157:H7, 0.61 to 0.71 kGy for Salmonella, 0.53 to 0.57 for L. monocytogenes, and 0.56 to 0.60 for S. aureus. The MA had no effect on the radiation resistance of the pathogens. During a 2-week storage period under mild temperature abuse (10°C), none of the pathogens were able to proliferate on the frankfurter on a roll product, regardless of the MA used. However, application of sublethal doses of ionizing radiation resulted in increased mortality of the gram-positive pathogens L. monocytogenes and S. aureus during the storage period regardless of the MA. Although the pathogens were unable to proliferate on the frankfurter on a roll product during the storage period, application of a postpackaging intervention step was needed to actually inactivate the foodborne pathogens. Ionizing radiation used in combination with sodium diacetate and potassium lactate resulted in additional mortality of L. monocytogenes and S. aureus, independent of the MA, during the 2-week storage period.

Fresh Produce Food Safety Training Program and Curriculum Development for the Southeast

This project directly addresses national food safety “priority issues”. Project design incorporates food safety and food chain security as focal points of educational efforts, then initiates practical, producer-level research, teaching, and extension whereby food handling and safety issues are addressed in a systems context. The overall Project goals are (1) to deliver information about Fresh Produce Food Safety (“FPFS”) programs and principles defined in the FDA Guide to fresh fruit and vegetable handlers in the Southeastern United States, (2) to provide hands-on individual state assistance with FPFS program implementation, and (3) to determine the influence of packing line procedures on the survival of foodborne pathogens. Part of the education envisioned under the new grant is introducing the concepts of recall and traceback. These concepts, proposed for incorporation into a new Country of Origin Labeling (COOL) act being discussed for adoption, possibly in 2006, essentially allows for the traceback of food to its point of origin. Osborne and others published a new protocol last month as “Model Recall Program for the Fresh Produce Industry” and want to help growers stay ahead of the curve on these issues. As a consequence of this project, the region's commercial fresh fruit and vegetable handlers will acquire the knowledge and skills necessary to establish effective GAPs programs. Developing new GAPs programs to fit the specific needs of the packing and chain store operations in the Southeastern United States can significantly reduce the possibility of illness originating from Southeastern fresh fruit and vegetables. Delivering such programs will serve as a valuable training tool for fresh produce industries nationwide.

The survival of foodborne pathogens during domestic washing-up and subsequent transfer onto washing-up sponges, kitchen surfaces and food

In this study, the survival of Salmonella, Campylobacter and Escherichia coli O157: H7, when exposed to a range of constant temperatures (47–60 °C), in hard or soft water, in the presence/absence of detergent (0–0.3%) and organic matter, and during drying, was investigated. Further experiments used a washing-up process simulation, where soiled dishes contaminated with bacteria were washed in a bowl of warm water containing detergent. In addition, this study considered the risk of bacterial transfer onto (1) sterile dishes and sponges via contaminated water, (2) kitchen surfaces wiped with a contaminated sponge, (3) items placed in direct contact with a contaminated kitchen surface, (4) food placed on a contaminated dish or (5) dishes from contaminated food. A proportion of dishes remained contaminated with all pathogen types after a typical washing-up. Water hardness did not appear to affect survival. E. coli, and to a lesser extent Salmonella, survived towel- or air-drying on dishes and after towel-drying the cloth became contaminated on every occasion, regardless of the test organism. A proportion of sterile dishes washed after contaminated dishes became contaminated with pathogens but transfer from dishes onto food was rare. Washing-up sponges frequently became contaminated with pathogens. The results of this study highlight the potential for survival and cross contamination of food borne pathogens in the kitchen environment.