An in-use study of the relationship between bacterial contamination of food preparation surfaces and cleaning cloths

The relationship between bacterial contamination of food preparation surfaces and the cleaning cloths associated with these surfaces was investigated in a busy college kitchen. Cleaning cloths used in conjunction with detergent became heavily contaminated within hours of first use. Following 'cleaning' with these cloths with detergent, both surfaces and cloths were found to be more heavily contaminated and there was evidence of contamination transfer to and from cloths and surfaces. Following 'cleaning' with cloths impregnated with quaternary ammonium disinfectant, there was a significant reduction in contamination on both surfaces and cloths, together with a reduction in the numbers of enterobacteria and pseudomonads. The results suggest that significant improvements in kitchen hygiene could be achieved by ensuring that contaminated cloths are not used for food preparation activities.     

Achieving hygiene in the domestic kitchen: the effectiveness of commonly used cleaning procedures

AIMS: To quantify the transmission of Salmonella and Campylobacter to hands, cloths, and hand- and food-contact surfaces during the preparation of raw poultry in domestic kitchens, and to examine the impact on numbers of these bacteria of detergent-based cleaning alone, or in conjunction with thorough rising. METHODS AND RESULTS: Groups of volunteers prepared chickens for cooking. Surfaces were sampled either before cleaning or after cleaning using water and detergent with or without thorough rinsing. Although cleaning followed by rinsing consistently achieved decontamination of surfaces contaminated with Campylobacter, significant numbers of surfaces were still contaminated with low numbers of Salmonella. Where cloths contaminated with Salmonella were stored overnight, a reduction in the efficacy of detergent-based cleaning regimes was observed. CONCLUSIONS: Rinsing is the critical step in ensuring that bacteria are removed from surfaces during cleaning, but this may still leave residual contamination. Growth of Salmonella occurs in some contaminated cloths during overnight storage; Salmonella on cloths stored overnight are also more difficult to remove by washing. SIGNIFICANCE AND IMPACT OF THE STUDY: Rinsing, as part of the cleaning process, is a critical step in achieving hygiene in the kitchen. However, to achieve completely hygienic surfaces, the use of an antimicrobial agent may be necessary.     

Kitchen hygiene in daily life

More and more data are available indicating that numerous (infectious) diseases are related to the home environment. Airborne microorganisms (bacteria, fungi), mites (in sheets or carpets), and (parts of) insects and beetles may be the cause of respiratory diseases such as asthma. In Europe and North America, more than half of the registered food infections appear to be contracted in the home. Then there is the development of new pathogens or the adaptation of microorganisms to extreme conditions. In many cases, the occurrence of adapted or resistant microorganisms is a reaction to the changing environment. Examples of this are the growth of Listeria monocytogenes in refrigerated food products and the presence of Legionella pneumophila in systems containing stagnant water.The main sources of infection in the domestic environment are people, pests, pets, and contaminated food and water. Germs are transmitted by direct contact with people or animals, by contaminated food, water, surfaces and air.Under circumstances favourable to microorganisms, the cells are able to survive or multiply into large numbers. Especially in places which stay moist for a long time considerable amounts of microorganisms are found, among with pathogenic types.The phrase ‘home hygiene’ does not merely refer to cleaning the house (daily). In practice, cleaning is not the only important issue; knowing how to prevent contamination is just as crucial. Domestic hygiene is the total sum of the measures used to prevent (insofar as possible) contamination with pathogens, and thus decreasing the number of infectious diseases. The hygiene measures required can be divided into three groups:

• Hygiene during food preparation.

• Personal and sanitary hygiene.

• Domestic environment.

This contribution will focus on food storage, food preparation and the effect of 'hygienic cleaners’ in the domestic kitchen.     

The effects of cleaning and disinfection in reducing Salmonella contamination in a laboratory model kitchen

AIMS: To establish a laboratory model to compare the effectiveness of detergent-based disinfection procedures for reducing cross-contamination risks during handling of contaminated chicken. METHODS AND RESULTS: During handling of chickens, artificially contaminated with Salmonella enteritidis PT4, the organism was widely spread to hands, cloths, and hand- and food-contact surfaces. Hygiene procedures were assessed on the basis of their ability to reduce the number of recoverable salmonellas to <1 CFU. Although detergent-based cleaning using a typical bowl-wash routine without rinsing produced some risk reduction (from 100 to 61.4% of contaminated surfaces), it was insufficient to consistently restore surfaces to a hygienic state. By combining detergent-based cleaning with a rinsing step or with hypochlorite at 500 ppm (of available chlorine) some further reduction in microbial risk was achieved, but was not considered satisfactory for food hygiene purposes. By contrast the risk reduction produced by hypochlorite at 5000 ppm was highly significant and was sufficient to reduce the number of contaminated surfaces to 2.9%. CONCLUSIONS: A key step in achieving a hygienic state through detergent-based cleaning is rinsing but even this will not produce a 'hygienic' result for difficult surfaces such as the chopping board or the dishcloth. Disinfectant compounds should be considered in order to reduce the potential for foodborne cross infection within the home environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Although tests are available to determine the performance of disinfectants, there are no quantitative procedures available to compare the risk reduction achieved by disinfection with that produced by detergent-based procedures. This study describes a reproducible laboratory method which can be used to differentiate the effectiveness of different hygiene procedures for reducing cross-contamination risks during food handling.     

The microbiological quality of washing-up water and the environment in domestic and commercial kitchens

AIMS: To determine the microbiological quality of washing-up water and the environment in domestic and commercial kitchens. METHODS AND RESULTS: Chicken meals were prepared by people without food safety training in their own kitchen (n = 52) or by trained staff in a commercial kitchen (n = 10). Study participants then washed-up, cleaned the kitchen and completed a food hygiene questionnaire. The temperature and microbiological quality of the washing-up water, and the presence of pathogens in dishcloths, tea towels and other kitchen samples was determined. Of the raw chickens used in meal preparation, 96 and 13% were naturally contaminated with Campylobacter or Salmonella spp., respectively. In domestic kitchens, two of 45 sponges, dishcloths or scourers and one of 32 hand- or tea towels were contaminated with Campylobacter after washing-up and cleaning but none of the tap or sink swabs yielded pathogens. The mean washing-up water temperature in the domestic kitchens was 40.7 degrees C, whereas in the commercial kitchen it was 44.7 degrees C (P = 0.04). Study participants who used hotter water (>/=40 degrees C) had lower levels of bacteria in their washing-up water. The aerobic plate counts of the washing-up water samples in domestic homes were usually between 105 and 106 CFU ml-1 but those associated with the commercial kitchen were consistently lower (P = 0.01). Despite this, Campylobacter was detected in one of 10 washing-up water samples from the commercial kitchen but in none of the samples from domestic kitchens. CONCLUSIONS: Pathogenic microorganisms can be recovered relatively frequently from the kitchen environment. SIGNIFICANCE AND IMPACT OF STUDY: By identifying factors that affect the number of microorganisms in washing-up water and the kitchen environment, evidence-based recommendations on implementing domestic food hygiene can be made.     

The survival and transfer of microbial contamination via cloths, hands and utensils

Survival and transfer of bacteria from laminated surfaces and cleaning cloths were investigated under laboratory conditions. Drying produced substantial reductions in numbers of recoverable organisms and achieved satisfactory decontamination of clean laminate surfaces. On soiled surfaces and on clean and soiled cloths, Gram-positive and some Gram-negative species survived for up to 4 h, and in some cases up to 24 h. Where contaminated surfaces or cloths came into contact with the fingers, a stainless steel bowl, or a clean laminate surface, organisms were transferred in sufficient numbers to represent a potential hazard if in contact with food.     

The survival and transfer of microbial contamination via cloths, hands and utensils

Survival and transfer of bacteria from laminated surfaces and cleaning cloths were investigated under laboratory conditions. Drying produced substantial reductions in numbers of recoverable organisms and achieved satisfactory decontamination of clean laminate surfaces. On soiled surfaces and on clean and soiled cloths, Gram-positive and some Gram-negative species survived for up to 4 h, and in some cases up to 24 h. Where contaminated surfaces or cloths came into contact with the fingers, a stainless steel bowl, or a clean laminate surface, organisms were transferred in sufficient numbers to represent a potential hazard if in contact with food.     

The importance of hygiene in modern society

At first sight, hygiene in our modern world seems to be rather satisfactory. Nevertheless, vulnerable groups are increasing in our society, which means that hygiene is a crucial factor in the well-being of the many people involved. Moreover, in the Netherlands, for instance, there are an estimated 2 million food-borne infections every year, of which 30 to 50% is supposed to find its origin in family homes. This indicates that important factors in daily life such as food preservation and preparation generally are far from hygienic. This is probably due to contaminated foodstuffs on one hand, and on the other a serious lack of knowledge in the population about food handling and preservation, as well as about cleaning and disinfection procedures.Inadequate knowledge can also lead to hygiene problems when dealing with modern technical facilities in the home like humidifiers, refrigerators and microwave ovens, airconditioning systems and hot water supplies. Micro-organisms are very flexible and can adapt themselves very rapidly to any new situation that is created by man. Excessive insulation of homes may lead to increased internal humidity, the occurrence of house dust mites and moulds, and, as a consequence, increased incidence of allergy symptoms. All new and old hazards should be dealt with, for instance by education of the general population, proper hygiene design, as well as adequate cleaning techniques in order to reach and maintain the hygiene level that is generally required.     

The Detection of Microorganisms and Organic Material on Stainless Steel Food Contact Surfaces

Few methods are available for the differentiation of microorganism and organic material on surfaces, although such mixtures are commonplace, particularly in the food industry, where food debris (soil) and microorganisms frequently foul food contact surfaces and pose challenges in terms of hygiene and cleanability. It would be of value to discern any differences in removal or persistence on surfaces. This review considers some methods which are available. Direct epifluorescence microscopy (DEM) enables visual differentiation, but traditional microbiological culture methods cannot detect organic soil. Atomic force microscopy (AFM) provides images of the surface on the nanometer scale, with minimal preparation, and is able to visualise both cellular and acellular components of the mixture, particularly prior to cleaning. Confocal laser scanning microscopy (CLSM) also has potential in this area. Surface sensitive methods such as X-Ray photoelectron spectroscopy (XPS) and Time-of-flight secondary ion mass spectrometry (ToFSIMS) provide information on chemical species present on a surface. Those chemical species more likely on microbial cells may be differentiated from those more likely in a specified organic soil, thus comparisons may be made as to differential removal of the organic soil and microbial cells. These methods may be of value in studies on the fouling and cleanability of surfaces.     

Do European Standard Disinfectant tests truly simulate in‐use microbial and organic soiling conditions on food preparation surfaces?

Aims: The results from European standard disinfectant tests are used as one basis to approve the use of disinfectants in Europe. The design of these laboratory‐based tests should thus simulate as closely as possible the practical conditions and challenges that the disinfectants would encounter in use. No evidence is available that the organic and microbial loading in these tests simulates actual levels in the food service sector. Methods and Results: Total organic carbon (TOC) and total viable count (TVC) were determined on 17 visibly clean and 45 visibly dirty surfaces in two restaurants and the food preparation surfaces of a large retail store. These values were compared to reference values recovered from surfaces soiled with the organic and microbial loading, following the standard conditions of the European Surface Test for bactericidal efficacy, EN 13697. Conclusions: The TOC reference values for clean and dirty conditions were higher than the data from practice, but cannot be regarded as statistical outliers. This was considered as a conservative assessment; however, as additional nine TOC samples from visibly dirty surfaces were discarded from the analysis, as their loading made them impossible to process. Similarly, the recovery of test organisms from surfaces contaminated according to EN 13697 was higher than the TVC from visibly dirty surfaces in practice; though they could not be regarded as statistical outliers of the whole data field. No correlation was found between TVC and TOC in the sampled data, which re‐emphasizes the potential presence of micro‐organisms on visibly clean surfaces and thus the need for the same degree of disinfection as visibly dirty surfaces. Significance and Impact of the Study: The organic soil and the microbial burden used in EN disinfectant standards represent a realistic worst‐case scenario for disinfectants used in the food service and food‐processing areas.     

Dietary change and the effects of food preparation on microwear patterns in the Late Neolithic of abu Hureyra, northern Syria

Comparison of the microwear features created on the occlusal surfaces of molar teeth from different cultural horizons at abu Hureyra, northern Syria, indicates that the hardness of the food eaten changed profoundly after the introduction of domestic cereal grains at the beginning of the Neolithic (Neolithic 2A), and again after the introduction of pottery in Neolithic 2C times. Comparison with the microwear features on the teeth of human groups known to eat cooked food demonstrated the identity of the microwear on the abu Hureyra teeth from the pottery levels with those who had eaten cooked food. It is suggested that the evidence for an increase in the population in Neolithic 2C times is a direct consequence of changes in food preparation techniques.     

Efficacies of Sodium Hypochlorite and Quaternary Ammonium Sanitizers for Reduction of Norovirus and Selected Bacteria during Ware-Washing Operations

Cross-contamination of ready-to-eat (RTE) foods with pathogens on contaminated tableware and food preparation utensils is an important factor associated with foodborne illnesses. To prevent this, restaurants and food service establishments are required to achieve a minimum microbial reduction of 5 logs from these surfaces. This study evaluated the sanitization efficacies of ware-washing protocols (manual and mechanical) used in restaurants to clean tableware items. Ceramic plates, drinking glasses and stainless steel forks were used as the food contact surfaces. These were contaminated with cream cheese and reduced-fat milk inoculated with murine norovirus (MNV-1), Escherichia coli K-12 and Listeria innocua. The sanitizing solutions tested were sodium hypochlorite (chlorine), quaternary ammonium (QAC) and tap water (control). During the study, the survivability and response to the experimental conditions of the bacterial species was compared with that of MNV-1. The results showed that current ware-washing protocols used to remove bacteria from tableware items were not sufficient to achieve a 5 log reduction in MNV-1 titer. After washing, a maximum of 3 log reduction in the virus were obtained. It was concluded that MNV-1 appeared to be more resistant to both the washing process and the sanitizers when compared with E. coli K-12 and L. innocua.     

Cleaning and decontamination efficacy of wiping cloths and silver dihydrogen citrate on food contact surfaces

Aims: To test the efficacy of four wipe cloth types (cotton bar towel, nonwoven, microfibre and blended cellulose/cotton) with either quaternary ammonia cleaning solution or silver dihydrogen citrate (SDC) in cleaning food contact surfaces. Methods: Swab samples collected from untreated, cloth‐treated and cloth disinfectant‐treated surfaces were subjected to hygiene monitoring using adenosine triphosphate (ATP) bioluminescence and aerobic total plate counting (TPC) assays. Results: Adenosine triphosphate measurements taken after wiping the surfaces showed poor cleaning by nonwoven cloths (2·89 RLU 100 cm^?2) than the microfibre (2·30 RLU 100 cm^?2), cotton terry bar (2·26 RLU 100 cm^?2) and blended cellulose/cotton cloth types (2·20 RLU 100 cm^?2). The cellulose/cotton cloth showed highest log reduction in ATP‐B RLU values (95%) and CFU values (98·03%) when used in combination with SDC disinfectant. Conclusions: Cleaning effect of wiping cloths on food contact surfaces can be enhanced by dipping them in SDC disinfectant. ATP‐B measurements can be used for real‐time hygiene monitoring in public sector, and testing microbial contamination provides more reliable measure of cleanliness. Significance and Impact of the Study: Contaminated food contact surfaces need regular hygiene monitoring. This study could help to estimate and establish contamination thresholds for surfaces at public sector facilities and to base the effectiveness of cleaning methods.     

Microbiological Contamination of Reindeer Carcass During Slaughter

Microbiological counts for 10 different sampling sites of 28 reindeer carcasses were studied in 3 reindeer slaughterhouses in Finland. On each carcass the hindshank, round, abdomen, flank, brisket, foreleg, shoulder, neck, foreback and back were sampled immediately after slaughter, using a nondestructive swabbing method. The overall mean bacterial count for 10 sampling sites of reindeer carcasses was 1.51 ± 0.51 log10 cfu/cm2. Statistically significant differences were detected between sampling sites. The back part of the reindeer carcass, i.e. hindshank, round, back and foreback, seemed to be relatively clean. The most contaminated parts were the foreleg, brisket and abdomen (2.05–2.95 log10 cfu/cm2); these could be used for monitoring the hygiene of the reindeer carcass after slaughter. Differences between the 3 slaughterhouses were detected for some sampling sites, which may be due to differences in slaughter techniques and hygiene.     

Listeria monocytogenes Can Form Biofilms in Tap Water and Enter Into the Viable but Non-Cultivable State

Listeria monocytogenes is a foodborne pathogen that can be transmitted through contaminated raw food or by ready-to-eat products that have been in contact with contaminated surfaces. Tap water (TW) is used to wash produce, as a processed food constituent and to wash processing surfaces and floors. The main aim of this work was to investigate the formation and survival of L. monocytogenes biofilms on stainless steel (SS) coupons in TW at 4, 22, 30 and 37 °C. For that, coupons with biofilm were visualised in situ while other coupons were scraped to quantify total cells by SYTO 9, cultivable numbers by plating onto brain heart infusion agar and viable numbers by the direct viable count method. Results showed that L. monocytogenes can form biofilms on SS surfaces in TW at any temperature, including at 4 °C. The number of total cells was similar for all the conditions tested while cultivable numbers varied between the level of detection (<8.3 CFU cm^?2) and 3.5?×?10⁵ CFU cm^?2, meaning between 7.0?×?10⁴ and 1.1?×?10⁷ cells cm^?2 have entered the viable but non-cultivable (VBNC) state. This work clearly demonstrates that L. monocytogenes can form biofilms in TW and that sessile cells can remain viable and cultivable in some conditions for at least the 48 h investigated. On the other hand, VBNC adaptation suggests that the pathogen can remain undetectable using traditional culture recovery techniques, which may give a false indication of processing surface hygiene status, leading to potential cross-contamination of food products.     

Assessment of microbiological quality of food preparation process in some restaurants of Makkah city

Microbiological contamination of food processing surfaces and utensils increases considerably the risk of food-borne illnesses via cross-contamination. Hence, the safety of served meals and beverages can be evaluated through the assessment of the microbiological quality of food contact surfaces in food-serving establishments. This study carried out in Makkah city aimed to assess the microbiological contamination levels on food processing surfaces and utensils in 43 restaurants from the 9 main districts in the city. A total of 294 swab preparations were taken from 16 types of food contact surfaces including cutting boards, food containers, knives, serving dishes and other utensils were examined. Ninety samples (31%) showed more than 10 CFU/cm² which were considered positive for microbiological contamination. Meat chopping devices and cutting boards were found as the most contaminated food contact surfaces (60% and 50%), while washed serving dishes and fridge handles were the least contaminated (21% and 18%). Microorganisms detected in the study were Klebsiella spp. (18.7%), Escherichia coli (17,7%), Staphylococcus aureus (4,4%), Pseudomonas spp. (1.7%), Proteus spp. (0.7%), Bacillus cereus (0.7%), and Candida sp. (0.3%). Klebsiella spp. and E. coli were observed in at least one sample from each of the sixteen different food contact surfaces. The incidence of restaurants with contaminated food contact surfaces was significantly variable among the different districts, with a value as high as 57% in the most affected district and 20% in the less affected. No contamination with Salmonella spp. or Listeria spp. was detected, however, the detection of Bacillus cereus, a toxin-forming microorganism, in two different restaurants underlines the need for continuous microbiological assessment to ensure standard sanitation levels in restaurants and catering establishments of Makkah city.     

Sampling strategy,occurrence and diversity of free‐living protozoa in domestic refrigerators

Aims: Evaluation of a sampling method to recover free‐living protozoa (FLP) from plastic surfaces. Application of the method on different areas inside domestic refrigerators. Methods and Results: Plastic coupons seeded with representatives of FLP were swabbed with cotton wools. The recovery efficiency was the highest for Chilomonas paramecium, followed by Tetrahymena pyriformis and the lowest for Acanthamoeba polyphaga. From 43 refrigerators, 19 and 26 were considered FLP positive when sample cultures were incubated at 7°C and 20°C, respectively. The number of FLP‐positive cultures was the highest in samples taken from vegetable trays followed by discharge gutters, whereas interior walls were rarely FLP positive. Higher numbers of taxa were observed in enrichment cultures incubated at 20°C instead of 7°C. The combination of microscopy and denaturing gradient gel electrophoresis revealed that discharge gutters occasionally were contaminated with a persistent protozoan population of flagellates (Cercozoa) and amoebae (Tubulinea). The FLP‐positive status of refrigerator surfaces was correlated with a high aerobic plate count. Conclusions: The cotton wool sampling method is useful to sample FLP from plastic surfaces. FLP are part of the microbial communities in domestic refrigerators. Significance and Impact of the Study: Knowledge on the occurrence of FLP in food‐related indoor environments is scarce. For the first time, a high protozoan diversity in domestic refrigerators is described.     

Food safety behaviour and handling practices among Saudi women during the COVID-19 pandemic

Although it is commonly known that viruses cannot multiply in food as they need a living host for growth, adenoviruses and corona viruses can reportedly survive on surfaces and food packages for several days. Therefore, food item mishandling could increase the risk of infection. In this cross-sectional study, we assessed the changes in the food purchasing habits, food safety behavior, and food handling practices among Saudi women during the COVID-19 pandemic. The study included 1356 women who were randomly approached via convenience sampling using an anonymous questionnaire distributed through various social media platforms. The variables were described in terms of frequency and percentage, and the Chi-square test was applied to assess the relationship between the dependent and independent variables. Approximately 62.5% of the participants were aware that SARS-CoV-2 is not transmitted via food. Most participants (90%) reported a shift from outdoor to indoor meal preparation, along with avoidance of visits to grocery stores for food purchase (55%) and increased usage of online grocery delivery services (27%). Most participants obtained good overall scores for food safety behavior during grocery shopping (mean score: 10.83±1.62/12 points, 90.25%), grocery unpacking at home (10.60±2.65/13 points, 81.55%), and personal hygiene (28.84±3.16/36 points, 80%). However, a moderate overall score was obtained for food preparation practices (7.77 ±1.91/12 points, 77.7%). Older and/or retired individuals, patients with chronic diseases, and/or individuals living with children showed better food safety behavior and handling practices compared to their counterparts. This study reported good overall food safety behavior and handling practice scores among participants under most categories studied. However, our results highlight the need for more customized public education programs for Saudi women, who are the primary food handlers in most households, particularly during food preparation, to further improve food safety practices and prevent potential food mishandling, which will eventually help preventing the spread of COVID-19.     

Bacterial contamination on touch surfaces in the public transport system and in public areas of a hospital in London

Aims:  To investigate bacterial contamination on hand-touch surfaces in the public transport system and in public areas of a hospital in central London.
Methods and Results:  Dipslides were used to sample 118 hand-touch surfaces in buses, trains, stations, hotels and public areas of a hospital in central London. Total aerobic counts were determined, and Staphylococcus aureus isolates were identified and characterized. Bacteria were cultured from 112 (95%) of sites at a median concentration of 12 CFU cm⁻². Methicillin-susceptible Staph. aureus (MSSA) was cultured from nine (8%) of sites; no sites grew methicillin-resistant Staph. aureus (MRSA).
Conclusions:  Hand-touch sites in London are frequently contaminated with bacteria and can harbour MSSA, but none of the sites tested were contaminated with MRSA.
Significance and Impact of the Study:  Hand-touch sites can become contaminated with staphylococci and may be fomites for the transmission of bacteria between humans. Such sites could provide a reservoir for community-associated MRSA (CA-MRSA) in high prevalence areas but were not present in London, a geographical area with a low incidence of CA-MRSA.