A case-control study of domestic kitchen microbiology and sporadic Salmonella infection

An Investigation into the Critical Factors Influencing the Spread of Campylobacter during Chicken Handling in Commercial Kitchens in China

Campylobacteriosis is the most common cause of bacterial gastroenteritis worldwide. Consumption of chicken meat is considered the main route for human infection with Campylobacter. This study aimed to determine the critical factors for Campylobacter cross-contamination in Chinese commercial kitchens during chicken handling. Five commercial kitchens were visited to detect Campylobacter occurrence from 2019 to 2020. Chicken samples (n = 363) and cotton balls from the kitchen surfaces (n = 479) were collected, and total bacterial counts and Campylobacter spp. were detected. Genotypic characterization of 57 Campylobacter jejuni isolates was performed by multilocus sequence typing (MLST). In total, 77.41% of chicken carcass samples and 37.37% of kitchen surfaces showed Campylobacter spp. contamination. Before chicken preparation, Campylobacter spp. were already present in the kitchen environment; however, chicken handling significantly increased Campylobacter spp. prevalence (p < 0.05). After cleaning, boards, hands, and knives still showed high bacterial loads including Campylobacter spp., which related to poor sanitary conditions and ineffective handling practices. Poor sanitation conditions on kitchen surfaces offer greater opportunities for Campylobacter transmission. Molecular typing by MLST revealed that Campylobacter cross-contamination occurred during chicken preparation. The most prevalent sequence types, ST693 and ST45, showed strong biofilm formation ability. Consequently, sanitary condition of surfaces and biofilm formation ability of isolates were the critical points contributing to spread of Campylobacter in kitchen environment. These results provide insight into potential targeted control strategies along the farm-to-plate chain and highlight the necessity for improvements in sanitary conditions. The implementation of more effective cleaning measures should be considered to decrease the campylobacteriosis risk.

Development and Piloting of a Food Safety Audit Tool for the Domestic Environment

Research suggests that consumers often mishandle food in the home based on survey and observation studies. There is a need for a standardized tool for researchers to objectively evaluate the prevalence and identify the nature of food safety risks in the domestic environment. An audit tool was developed to measure compliance with recommended sanitation, refrigeration and food storage conditions in the domestic kitchen. The tool was piloted by four researchers who independently completed the inspection in 22 homes. Audit tool questions were evaluated for reliability using the κ statistic. Questions that were not sufficiently reliable (κ < 0.5) or did not provide direct evidence of risk were revised or eliminated from the final tool. Piloting the audit tool found good reliability among 18 questions, 6 questions were revised and 28 eliminated, resulting in a final 24 question tool. The audit tool was able to identify potential food safety risks, including evidence of pest infestation (27%), incorrect refrigeration temperature (73%), and lack of hot water (>43 °C, 32%). The audit tool developed here provides an objective measure for researchers to observe and record the most prevalent food safety risks in consumer's kitchens and potentially compare risks among consumers of different demographics.

Microbiological safety of domestic refrigerators and the dishcloths used to clean them in Guadalajara, Jalisco, Mexico

Household refrigerators are a potential pathogen contamination source for foods. An evaluation of the microbiological safety of 200 refrigerators in Guadalajara, Jalisco, Mexico, was made by visual inspection, ATP-bioluminescence levels, indicator microorganisms including Escherichia coli and Staphylococcus aureus, and the presence of Listeria monocytogenes and Salmonella. Additionally, interviews of the owners of the refrigerators were carried out to determine relationships between food storage practices, demographic aspects, and microbiological status. Dishcloths used to clean refrigerators were also analyzed. Operational conditions (cleanliness, fullness, organization, frequency of cleaning, and temperature) were evaluated by trained observers. Results showed deficient cleanliness in 55% of refrigerators, 22% were completely full, 43% very disorganized, 28% were usually cleaned only once in 3 to 6 months, and 53% had internal temperatures >7.1°C. ATP-bioluminescence levels were >300 relative light units on 67 and 74% of shelves and drawers, respectively, indicating that surfaces were dirty according to the luminometer manufacturer. Psychrotrophic aerobic bacteria counts on shelves, drawers, and dishcloths were 6.3, 5.2, and 6.3 log CFU/cm(2); for coliform bacteria, 5.2, 3.9, and 4.7 CFU/cm(2); for E. coli, 3.7, 3.5, and 4.8 CFU/cm(2); and for Staphylococcus aureus, 2.1, 2.5, and 2.3 CFU/cm(2), respectively. L. monocytogenes and Salmonella were isolated from 59.5, 20.5, and 17% and 32.5, 8.0 and 12.5% of shelves, drawers, and dishcloths, respectively. Four Salmonella serotypes and nine serogroups (partially serotyped isolates) were identified. The most prevalent were Salmonella Anatum (39.5%), Salmonella group E1 (19.7%), and Salmonella group E1 monophasic (12.5%). Operational conditions and microbiological status were clearly deficient in sampled refrigerators, highlighting the consequent risk of foodborne disease among users. Educational programs are needed to improve the domestic food safety in Mexico.

Transfer of Salmonella Enteritidis to four types of surfaces after cleaning procedures and cross-contamination to tomatoes

The objectives of the present study were to evaluate the spread of Salmonella Enteritidis to different cutting boards (wood, triclosan-treated plastic, glass, and stainless steel) from contaminated poultry skin (5 log CFU/g) and then to tomatoes and to analyze the effect of different protocols used to clean these surfaces to control contamination. The following procedures were simulated: (1) no cleaning after handling contaminated poultry skin; (2) rinsing in running water; (3) cleaning with dish soap and mechanical scrubbing; and (4) cleaning with dish soap and mechanical scrubbing, followed by disinfection with hypochlorite. The pathogen was recovered from all surfaces following procedure 1, with counts ranging from 1.90 to 2.80 log, as well as from the tomatoes handled on it. Reduced numbers of S. Enteritidis were recovered using the other procedures, both from the surfaces and from the tomatoes. Counts were undetectable after procedure 4. From all surfaces evaluated, wood was the most difficult to clean, and stainless steel was the easiest. The use of hypochlorite as a disinfecting agent helped to reduce cross-contamination.

Seasonality in human salmonellosis: assessment of human activities and chicken contamination as driving factors

This study used integrated surveillance data to assess the seasonality in retail chicken contamination and of human activities and their role on the seasonality of human endemic salmonellosis. From June 2005 to May 2008, reported cases of salmonellosis were followed-up comprehensively using a standardized questionnaire, and 616 retail chicken breasts were systematically tested for Salmonella, in one Canadian community. Poisson regression was used to model seasonality of human cases, Salmonella in retail chicken, and to assess the relationship between these and selected meteorological variables. The case-case approach was used to compare the activities of salmonellosis cases that occurred during the summer peak to the other cases. There were 216 human endemic salmonellosis cases (incidence rate: 14.7 cases/100,000 person-years), predominantly of Typhimurium and Enteritidis serotypes (28.4% and 20.8%, respectively). The monthly distribution of cases was associated with ambient temperature (p < 0.001) with a significant seasonal peak in June (p = 0.03) and July (p = 0.0005), but it was not associated with precipitation (p = 0.38). Several activities reported by cases tended to be more frequent during summer. Particularly, attending a barbeque and gardening within the 3 days before the disease onset were two significant risk factors for salmonellosis in June or July compared with the salmonellosis cases that occurred in the other months. Out of all chicken samples, 185 (30%) tested positive for Salmonella spp., Kentucky being the dominant serotype (44.3% of positive samples). The monthly proportion of positive chicken samples showed no seasonal variations (p = 0.30) and was not associated with the monthly count of human cases (p = 0.99). In conclusion, even though evidence generally supports chicken as a primary vehicle of Salmonella to humans, the contamination of retail chicken was not driving the seasonality in human salmonellosis. Attending a barbeque or gardening during the hotter months of the year should be further assessed for their risk.

Case-control study of disease determinants for non-typhoidal Salmonella infections among Michigan children

Background

Infections with Salmonella serotypes continue to be a significant global public health problem. In addition to contaminated foods, several other sources contribute to infections with Salmonella serotypes. We have assessed the role of socioeconomic factors, exposure to food, and environmental sources in the etiology of non-typhoidal Salmonella infections in Michigan children.

Findings

A case-control study among Michigan children aged ≤ 10 years was conducted. A total of 123 cases of children with laboratory-confirmed Salmonella infections and 139 control children, who had not experienced symptoms of gastrointestinal illness during the month prior to the interviews, were enrolled. The cases and controls were matched on age-category (<1 year, 2-<6 years and 6-10 years). Data on socioeconomic status, food intake, and environmental exposures, were collected on the queried case and control subjects. After adjusting for race and household-income the final regression multivariable model revealed that Salmonella infections were significantly associated with attendance of a daycare center (adjusted matched odds ratio = 5.00, 95% CI: 1.51 - 16.58), contact with cats (MOR = 2.53, 95% CI: 1.14 - 5.88), and contact with reptiles (MOR = 7.90, 95% CI: 1.52 - 41.01), during the 3 days prior to the onset of child's illness.

Conclusions

Study results suggest that exposure to environmental sources may play an important role in sporadic infections with Salmonella serotypes in children. Additional efforts are needed to educate parents and caretakers about the risk of Salmonella transmission to children from these sources.

How effective is good domestic kitchen hygiene at reducing diarrhoeal disease in developed countries? A systematic review and reanalysis of the UK IID study

Background

To assess whether domestic kitchen hygiene is an important contributor to the development of diarrhoea in the developed world.

Methods

Electronic searches were carried out in October 2006 in EMBASE, MEDLINE, Web of Knowledge, Cochrane central register of clinical trials and CINAHL. All publications, irrespective of study design, assessing food hygiene practices with an outcome measure of diarrhoea were included in the review. All included studies underwent data extraction and the data was subsequently analysed. The analysis was conducted by qualitative synthesis of the results. Given the substantial heterogeneity in study design and outcome measures meta-analysis was not done. In addition the existing dataset of the UK IID study was reanalysed to investigate possible associations between self-reported diarrhoea and variables indicative of poor domestic kitchen hygiene

Results

Some 14 studies were finally included in subsequent analyses. Of the 14 studies included in this systematic review, 11 were case-control studies, 2 cross-sectional surveys, and 1 RCT. Very few studies identified any significant association with good environmental kitchen hygiene. Although some of the variables in the reanalysis of the UK IID study were statistically significant no obvious trend was seen.

Conclusion

The balance of the available evidence does not support the hypothesis that poor domestic kitchen hygiene practices are important risk factors for diarrhoeal disease in developed countries.