Risk factors for the occurrence of sporadic Salmonella enterica serotype enteritidis infections in children in France: a national case-control study

A Review of Temperature, pH, and Other Factors that Influence the Survival of Salmonella in Mayonnaise and Other Raw Egg Products

Salmonellosis is one of the main causes of foodborne illnesses worldwide, with outbreaks predominately linked to contamination of eggs and raw egg products, such as mayonnaise. This review explores previous studies that have investigated Salmonella control mechanisms utilized in the production of raw egg mayonnaise and other food products. Apart from the use of pasteurized eggs, the main control mechanism identified is the pH of the raw egg products, which plays an important role in the consistency and stability while affecting the survival of Salmonella spp. However, currently there is no consensus regarding the critical pH limit for the control of Salmonella. The effectiveness of pH as a control mechanism is influenced by the type of acid used, with the effectiveness of lemon juice compared with vinegar highly debated. Additionally, Salmonella susceptibility to pH stresses may also be influenced by storage temperature (in some studies refrigeration temperatures protected Salmonella spp. from acidulants) and is further complicated by the development of Salmonella cross-tolerance-induced responses, pH homeostasis achieved by the cellular antiport and symport systems, and acid tolerance response (ATR). These mechanisms all provide Salmonella with an added advantage to ensure survival under various pH conditions. Other confounding factors include the fat content, and the addition of NaCl, garlic and plant essential oils (PEOs) from mint, cinnamon, cardamom and clove.

Sporadic salmonellosis in Lower Saxony, Germany, 2011-2013: raw ground pork consumption is associated with Salmonella Typhimurium infections and foreign travel with Salmonella Enteritidis infections

To investigate risk factors for sporadic salmonellosis, for each notified case four randomly selected population controls matched for age, sex and geographical region were interviewed via self-administered questionnaire. Conditional logistic regression analysis of 285 matched pairs revealed significant associations for raw ground pork consumption [odds ratio (OR) 6·0, 95% confidence interval (CI) 1·8-20·1], taking antacids (OR 5·8, 95% CI 1·4-24·5), eating meat outside the home (OR 5·7, 95% CI 2·2-14·6) and daily changing or cleaning of dishcloth (OR 2·1, 95% CI 1·2-3·9). Animal contact and ice cream consumption were negatively associated with salmonellosis (OR 0·5, 95% CI 0·2-1 and OR 0·3, 95% CI 0·1-0·6, respectively). S. Typhimurium infections were significantly associated with raw ground pork consumption (OR 16·7, 95% CI 1·4-194·4) and S. Enteritidis infections with having travelled abroad (OR 9·7, 95% CI 2·0-47·3). Raw egg consumption was not a risk factor, substantiating the success of recently implemented national control programmes in the poultry industry. Unexpectedly, hygienic behaviour was more frequently reported by cases, probably because they overestimated their hygiene precautions retrospectively. Although animal contact might enhance human immunocompetence, underreporting of salmonellosis by pet owners could have occurred. Eating raw pork products is the major risk factor for sporadic human S. Typhimurium infections in Lower Saxony.

Risk factors associated with sporadic salmonellosis in children: a case-control study in Lower Saxony, Germany, 2008–2011

We conducted a case-control study based on 884 laboratory-confirmed sporadicSalmonellacases reported to the German infectious disease notification system. For controls, we recruited 510 rotavirus cases via the same system. Univariable and multivariable logistic regression analyses were performed separately for children aged 0–3 years and 4–14 years. In both age groups, the highest odds ratios (OR) were found for raw ground pork consumption [0–3 years: OR 8·6, 95% confidence interval (CI) 2·4–30·8; 4–14 years: OR 4·5, 95% CI 1·1–19]. Further risk factors were exposure to animals (OR 1·6, 95% CI 1·1–2·1), consumption of poultry (OR 1·5, 95% CI 1·1–2·1), food items containing eggs (OR 1·5, 95% CI 1·1–2) and black pepper (OR 1·7, 95% CI 1·1–3·5) in children aged 0–3 years, and consumption of uncooked pork sausage (OR 3·6, 95% CI 1·4–9·3) in children aged 4–14 years. This study highlights the significance of raw pork products (‘Mett’ in German) as risk factors for sporadic salmonellosis in children in Germany.

Epidemiological investigation of an outbreak of salmonellosis in Gyeongju, Korea

Objectives

A salmonellosis outbreak occurred within a community of Gyeongju residents who ingested catered food from a wedding in June 2009. We aimed to epidemiologically investigate the probable vehicle of the infection.

Methods

We conducted a retrospective cohort study on 34 local residents who ingested the wedding food.

Results

Among the 34 residents, 31 (91.2%) reported symptoms of infection after eating the food. Among all of the wedding foods, pan-fried foods were highly associated with the diarrheal attack rate. On bacteriological examination, Salmonella species were detected in the pan-fried foods among the leftover foods and in 17 of the 31 stool specimens from the cases. There were five different types of pan-fried foods, but the onset of symptoms was independent of the ingredients used. We found that the pan-fried food was prepared at a food store in Seoul and that eggs were a common ingredient.

Conclusions

The major cause of the salmonellosis in this population was presumed to be the pan-fried food prepared with contaminated eggs. These food items might have been partially undercooked because of their irregular shape, which allowed the Salmonella species to survive and multiply before ingestion.

Case-control studies of sporadic enteric infections: a review and discussion of studies conducted internationally from 1990 to 2009

Epidemiologists have used case-control studies to investigate enteric disease outbreaks for many decades. Increasingly, case-control studies are also used to investigate risk factors for sporadic (not outbreak-associated) disease. While the same basic approach is used, there are important differences between outbreak and sporadic disease settings that need to be considered in the design and implementation of the case-control study for sporadic disease. Through the International Collaboration on Enteric Disease "Burden of Illness" Studies (the International Collaboration), we reviewed 79 case-control studies of sporadic enteric infections caused by nine pathogens that were conducted in 22 countries and published from 1990 through to 2009. We highlight important methodological and study design issues (including case definition, control selection, and exposure assessment) and discuss how approaches to the study of sporadic enteric disease have changed over the last 20 years (e.g., making use of more sensitive case definitions, databases of controls, and computer-assisted interviewing). As our understanding of sporadic enteric infections grows, methods and topics for case-control studies are expected to continue to evolve; for example, advances in understanding of the role of immunity can be used to improve control selection, the apparent protective effects of certain foods can be further explored, and case-control studies can be used to provide population-based measures of the burden of disease.

Risk factors for salmonella gastroenteritis in children less than five years of age in Taiwan

BACKGROUND

Nontyphoid Salmonella spp. have been among the most common pathogens of acute gastroenteritis in children in Taiwan. However, the principal sources of transmission remain poorly defined.

METHODS

A matched case-control study was conducted from January 2009 to October 2010. Cases were children aged 2-60 months who were hospitalized at 3 medical centers in Taiwan because of diarrhea and found to have culture-proven nontyphoidal Salmonella infection. Controls were healthy children or children with acute diseases other than gastroenteritis and matched to cases by age, gender, study site and enrollment date.

RESULTS

A total of 396 cases and 930 matched controls were included for analysis. Multivariate analysis using conditional logistic regression identified contact with household members having diarrhea (matched odds ratio [mOR], 17.9; 95% confidence interval [CI]: 8.82-36.34; P < 0.0001), consumption of instant powdered milk (mOR, 2.04; 95% CI: 1.05-3.94; P = 0.0344), visits to health-care facilities (mOR, 1.66; 95% CI: 1.12-2.48; P = 0.0126) and consumption of purchased groundwater (mOR, 1.50; 95% CI: 1.06-2.11; P = 0.0214) within 1 week preceding enrollment as independent factors associated with increased risk of salmonellosis. Hand washing before meals (P = 0.0311), breastfeeding (P = 0.0370), consumption of chicken (P = 0.0019) and consumption of food prepared by caregivers (P = 0.0011) were protective against Salmonella infection.

CONCLUSIONS

The principal transmission routes of Salmonella infection in Taiwanese children are person-to-person, waterborne and environmental contacts. The possibility of powdered milk and groundwater contamination of Salmonella cannot be excluded and requires further investigation.

Recent trends in the epidemiology of non-typhoidal Salmonella in Israel, 1999-2009

The aim of the present study was to assess the recent trends in the epidemiology of non-typhoid Salmonella in Israel using a sentinel laboratory-based surveillance network. Between 1999 and 2009, 8758 Salmonella stool isolates were reported by five sentinel laboratories. There was a significant decrease in the incidence rate of Salmonella isolates from 70·5/100,000 in 1999 to 21·6/100,000 in 2005 followed by a slight increase to 30·3/100,000 in 2009. Of all Salmonella, 64·3% were isolated from children in the 0-4 years age group. Up to 2008, S. Enteritidis was the most prevalent serotype and in 2009 S. Infantis emerged as the most common Salmonella serotype. The decrease in the incidence of S. Enteritidis and S. Typhimurium and increase in S. Infantis among humans were associated with a similar trend among breeding flocks, which followed significant preventive interventions conducted against S. Enteritidis and S. Typhimurium infections in poultry. Tight surveillance and education of food handlers and consumers should be enhanced to reduce the foodborne transmission of Salmonella in Israel.

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.

Drastic decrease of Salmonella Enteritidis isolated from humans in Belgium in 2005, shift in phage types and influence on foodborne outbreaks

In Belgium, non-typhoidal salmonellosis and campylobacteriosis are the two most frequently reported foodborne illnesses. During 2005, a 71% decrease of Salmonella Enteritidis infections compared with the average annual number cases in the period 2000-2004 was recorded by the Belgian National Reference Centre for Salmonella and Shigella. After the peak of 1999, the total number of salmonellosis cases decreased gradually, with the exception of 2003 when an increase was again recorded due to the rise of isolates belonging to the serotype Enteritidis. PT4, the predominant phage type of serotype Enteriditis over recent years (except in 2003), became the second most prevalent phage type in 2005 after PT21. We present in this paper the epidemiology (incidence and trends) of human salmonellosis in Belgium and assess the role of the vaccination programme in layer flocks on the decline of the incidence of human salmonellosis and foodborne outbreaks due to S. Enteritidis.

Evaluation of the impact on human salmonellosis of control measures targeted to Salmonella Enteritidis and Typhimurium in poultry breeding using time-series analysis and intervention models in France

In France, salmonellosis is the main cause of foodborne bacterial infection with serotypes Enteritis (SE) and Typhimurium (ST) accounting for 70% of all cases. French authorities implemented a national control programme targeting SE and ST in poultry and eggs from October 1998 onwards. A 33% decrease in salmonellosis has been observed since implementation. We designed an evaluation of the impact of this control programme on SE and ST human infections in France. Using monthly Salmonella human isolate reports to the National Reference Centre we defined two intervention series (SE and ST) and one control series comprising serotypes not know to be associated with poultry or eggs. The series, from 1992 to 2003, were analysed using autoregressive moving average models (ARMA). To test the hypothesis of a reduction of SE and ST human cases >0 after the programme started and to estimate its size, we introduced an intervention model to the ARMA modelling. In contrast to the control series, we found an annual reduction of 555 (95% CI 148-964) SE and of 492 (95% CI 0-1092) ST human infections, representing respectively a 21% and 18% decrease. For SE, the decrease occurred sharply after implementation while for ST, it followed a progressive decrease that started early in 1998. Our study, suggests a true relation between the Salmonella control programme and the subsequent decrease observed for the two targeted serotypes. For ST, however, the decrease prior to the intervention may also reflect control measures implemented earlier by the cattle and milk industry.

[Risk factors for the occurrence of sporadic Campylobacter, Salmonella and rotavirus diarrhea in preschool children]

BACKGROUND

Sporadic cases of diarrhea in preschool children are highly frequent, especially those caused by rotavirus, Campylobacter and Salmonella. The aim of this study was to identify some of the factors associated with these processes.

MATERIAL AND METHODS

A case-control study of hospitalized incident cases aged less than 3 years old was performed. Questionnaires were administered at admission, before the results of stool tests were known. Susceptibility, food exposure, and environmental factors were investigated. Infants aged less than 1 year were analyzed separately.

RESULTS

A total of 117 patients (rotavirus in 31, Campylobacter in 228 and Salmonella in 21, negative results in 37) and 84 controls were studied. Several protective factors, such as breast feeding and prior antibiotic use, were identified. Risk factors for diarrhea were exposure to meat products (eating or environmental exposure in the kitchen), some kinds of pets, and attendance at day care. Differences were found by etiology and age. In the culture-negative group, no risk factors were identified.

CONCLUSION

The problems posed by epidemiological study of this issue are discussed. The main findings in each group of cases are interpreted and proposals are made for their application in the control and prevention of these diseases.

Re-assessment of risk factors for sporadic Salmonella serotype Enteritidis infections: a case-control study in five FoodNet Sites, 2002-2003

Active surveillance for laboratory-confirmed Salmonella serotype Enteritidis (SE) infection revealed a decline in incidence in the 1990s, followed by an increase starting in 2000. We sought to determine if the fluctuation in SE incidence could be explained by changes in foodborne sources of infection. We conducted a population-based case-control study of sporadic SE infection in five of the Foodborne Diseases Active Surveillance Network (FoodNet) sites during a 12-month period in 2002-2003. A total of 218 cases and 742 controls were enrolled. Sixty-seven (31%) of the 218 case-patients and six (1%) of the 742 controls reported travel outside the United States during the 5 days before the case's illness onset (OR 53, 95% CI 23-125). Eighty-one percent of cases with SE phage type 4 travelled internationally. Among persons who did not travel internationally, eating chicken prepared outside the home and undercooked eggs inside the home were associated with SE infections. Contact with birds and reptiles was also associated with SE infections. This study supports the findings of previous case-control studies and identifies risk factors associated with specific phage types and molecular subtypes.

A case-control study of the epidemiology of sporadic Salmonella infection in infants

OBJECTIVE

Rates of Salmonella infection are highest in infants, but little is known about potential sources of infection in this high-risk population. We performed a case-control study to identify dietary and environmental risk factors for sporadic salmonellosis among infants.

PATIENTS AND METHODS

In 2002-2004, the Foodborne Diseases Active Surveillance Network conducted a population-based, case-control study of sporadic salmonellosis among infants <1 year of age in 8 states. Cases were identified via active laboratory-based surveillance. Healthy controls were frequency matched by age and identified through birth registries or published birth announcements. We assessed diet and environmental exposures in the 5 days before illness onset or interview. Data were analyzed by using logistic regression adjusting for age.

RESULTS

The study enrolled 442 subjects and 928 controls. Compared with healthy controls, infants with Salmonella infection were less likely to have been breastfed and more likely to have had exposure to reptiles, to have ridden in a shopping cart next to meat or poultry, or to have consumed concentrated liquid infant formula during the 5-day exposure period. Travel outside the United States was associated with illness in infants 3 to 6 and >6 months of age. Attending day care with a child with diarrhea was associated with salmonellosis in infants >6 months of age.

CONCLUSIONS

We identified a number of modifiable protective and risk factors for salmonellosis in infants. Attention should be directed at developing effective preventive measures for this high-risk population.

Demographic Risk Factors and Incidence of Salmonella Enteritidis Infection in Michigan

Salmonella Enteritidis is a major cause of foodborne disease worldwide. In the United States, this serotype has been associated with significant morbidity and mortality accounting for about 17% of all human Salmonella infections. Data on risk factors associated with serotype-specific Salmonella infections have not been reported in Michigan before. We carried out this study using surveillance data to identify high-risk groups and regions for S. Enteritidis infection in Michigan. Results of this study may be used to develop better control and prevention measures against this common foodborne pathogen. We analyzed data on Salmonella infections collected by the Michigan Department of Community Health's surveillance system (1995-2001). We computed age, gender, and place of residence-specific incidences of S. Enteritidis infection in Michigan using population-based denominators. We used Poisson regression analysis to study the associations between S. Enteritidis infection and certain predictor demographic variables, while controlling for confounders and covariates. We found an overall 1.87/100,000 average annual S. Enteritidis incidence with 1.91/100,000 in females and 1.81/100,000 in males. A higher incidence of S. Enteritidis infection was associated with Michigan children<5 years old when compared with average national estimates (p<0.01). The final adjusted Poisson model revealed that children<1 year of age [RR: 9.75, CI: 7.99-11.90] and children 1-4 years of age [RR: 3.37, CI: 2.83-4.02] are at higher risk for S. Enteritidis infection compared to adults aged 15-39 years. No significant differences in incidence of S. Enteritidis infections were found between urban and rural dwellers or between genders (p>0.05). The incidence rate of S. Enteritidis infection in the Michigan pediatric population (<5 years) was found to be significantly higher than average national estimates, meriting immediate public health attention. Risk factors for S. Enteritidis infection in Michigan children should be identified in order to devise effective control and prevention measures.

[Salmonella infections in children: a retrospective study over a four-year period]

OBJECTIVES

Epidemiological state of salmonella infections in Languedoc-Roussillon (France) and discussion of therapeutic indications.

MATERIAL AND METHOD

Retrospective study over a four-year period of paediatric salmonella infections requiring hospitalisation in Montpellier University Hospital. Analysis of clinical, bacteriological, laboratory and therapeutic data.

RESULTS

One hundred and sixty nine cases of paediatric salmonella infections have been investigated. The clinical triad consisted of diarrhea, abdominal pain and fever. Six severe cases have been observed and seemed to have been independent of patient's background. Laboratory findings showed inconstantly hyperleucocytosis and increase in CRP levels. Stool analysis remained the reference laboratory test to detect salmonella. Two major strains of salmonella have been identified: Salmonella enterica subsp. enterica serovar Typhimurium and Enteriditis. Treatments have been essentially symptomatic but 20% of the children (n=34) required antibiotic therapy. A favourable outcome was observed in all the children.

DISCUSSION

Incidence of salmonella infections is increasing in France, particularly in the Languedoc-Roussillon area. Diagnosis of mild forms is generally easy but certain patient background seems to expose to severe forms. Treatment of salmonella infections is mainly symptomatic, only severe or specific cases (young age, immunodepression...) requiring antibiotic treatment. The growing antibiotic use and the increasing of resistance are currently the main problems in the management of salmonella infections. Those infections remain a public health problem in Languedoc-Roussillon.

Egg consumption patterns and Salmonella risk in Finland

To estimate the consumer risk of contracting Salmonella infection via shell eggs and to evaluate the effect of possible preventative measures, quantitative microbiological risk assessment is being developed in Finland. As a part of the risk assessment, a survey of 918 respondents was conducted to study how households purchase, store, handle, and use eggs. In addition, suitability of the Internet as a survey method was compared with a postal survey. Shell eggs were usually purchased once every 2 weeks (41% of all the respondents). Ninety-one percent of the respondents bought eggs in groceries and 93% stored eggs at chilled temperatures. The majority of the respondents (80%) only had eggs in their home for which the best-before date had not expired. Only 34% of the respondents said that they always washed their hands after breaking eggs. Consumption of well-cooked eggs accounted for 84%, consumption of soft-boiled eggs for 12%, and consumption of raw eggs for 4% of the total amount of eggs consumed. The elderly used eggs more frequently than the whole population, but the consumption of raw egg dishes decreased with age. The Internet survey was a rapid method for transmitting information, but its response rate was low (9%), and it did not appear to be a suitable tool for data collection in a general population. The results indicate that although the majority of the respondents had safe egg-handling practices, a substantial minority of the consumers had risk-prone behavior.

Emergence of Salmonella enteritidis phage type 4 in the Caribbean: case-control study in Trinidad and Tobago, West Indies

A prospective case-control study involving 46 case patients and 92 age- and neighborhood-matched control subjects was conducted in Trinidad and Tobago (T&T) between March 1998 and May 1999 to determine the etiology, sources, and risk factors for Salmonella enteritidis (SE) infection. SE infection in T&T was found to be associated with the consumption of shell eggs, and in particular raw or undercooked eggs. SE isolates from 30 (88%) of 34 patients and from 9 implicated egg or egg-containing food samples were phage type 4. Homemade eggnog and ice cream, cake batter, and egg-containing beverages were the main raw egg-containing foods, reflecting the cultural practices of the people of T&T. Public health education on the risks of eating raw or undercooked eggs, thorough cooking of all egg dishes, and refrigeration of shell eggs and egg dishes; studies tracing infected eggs to their sources; and testing of flocks of layer chickens for SE are needed to reduce the incidence of this infection.

Risk factors for the occurrence of sporadic Salmonella enterica serotype typhimurium infections in children in France: a national case-control study

To determine risk factors for the occurrence of sporadic Salmonella typhimurium infections among children in France, we conducted a matched case-control study. Cases were identified between 15 June and 30 September 1996. We interviewed 101 pairs of case patients and control subjects, matched for age and place of residence. The risk of illness was greater for children who ate undercooked ground beef than for those who did not (odds ratio [OR], 5.0; 95% confidence interval [CI], 1.9-13.1). Case patients were more likely than control subjects to have taken antibiotics during the month before onset of disease (OR, 2.2; 95% CI, 1.0-4.9). Case patients <5 years of age were more likely to have been in contact with a household member with diarrhea 3-10 days before onset (P=.05). Consumption of undercooked ground beef is a risk factor for the sporadic occurrence of S. typhimurium infection among children, and antibiotics may facilitate the occurrence of illness. The possibility of person-to-person transmission among young children needs to be considered.

How many foodborne outbreaks of Salmonella infection occurred in France in 1995? Application of the capture-recapture method to three surveillance systems

Despite control measures, foodborne outbreaks of non-typhi Salmonella infection continue to occur in developed countries. The authors aimed to assess the number of foodborne Salmonella outbreaks that occurred in France in 1995 using a capture-recapture approach. Data from three sources--the National Public Health Network (NPHN), the Ministry of Agriculture (MA), which receives mandatory notification, and the National Salmonella and Shigella Reference Center (NRC)-were collected. Matching algorithms permitted identification of matched outbreaks. The total number of outbreaks was estimated by log-linear modeling taking into account source dependencies and the variable catchability. The final estimate was adjusted for the positive predictive value (66%) of the NRC case definition. The dependence between the NPHN and the MA was also evaluated by means of a qualitative survey. A total of 716 foodborne Salmonella outbreaks were reported to the three sources, and 108 matches were identified. The best-fitting model, taking into account a positive dependence between the NPHN and MA sources, gave an estimate of 757 outbreaks. The sensitivity was 15% for the NPHN, 10% for the MA, and 50% for the NRC. In France, routine mandatory reporting of foodborne Salmonella outbreaks is very incomplete, and it is not representative of the serotype and the type of outbreak.