The home environment and salmonellosis in children

Epidemiology of Salmonellosis Among Infants in the United States: 1968-2015

OBJECTIVES

Describe characteristics of gastroenteritis, bacteremia, and meningitis caused by nontyphoidal Salmonella among US infants.

METHODS

We analyze national surveillance data during 1968-2015 and active, sentinel surveillance data during 1996-2015 for culture-confirmed Salmonella infections by syndrome, year, serotype, age, and race.

RESULTS

During 1968-2015, 190 627 culture-confirmed Salmonella infections among infants were reported, including 165 236 (86.7%) cases of gastroenteritis, 6767 (3.5%) bacteremia, 371 (0.2%) meningitis, and 18 253 (9.7%) with other or unknown specimen sources. Incidence increased during the late 1970s-1980s, declined during the 1990s-early 2000s, and has gradually increased since the mid-2000s. Infants' median age was 4 months for gastroenteritis and bacteremia and 2 months for meningitis. The most frequently reported serotypes were Typhimurium (35 468; 22%) for gastroenteritis and Heidelberg for bacteremia (1954; 29%) and meningitis (65; 18%). During 1996-2015 in sentinel site surveillance, median annual incidence of gastroenteritis was 120, bacteremia 6.2, and meningitis 0.25 per 100 000 infants. Boys had a higher incidence of each syndrome than girls in both surveillance systems, but most differences were not statistically significant. Overall, hospitalization and fatality rates were 26% and 0.1% for gastroenteritis, 70% and 1.6% for bacteremia, and 96% and 4% for meningitis. During 2004-2015, invasive salmonellosis incidence was higher for Black (incident rate ratio, 2.7; 95% confidence interval, 2.6-2.8) and Asian (incident rate ratio, 1.8; 95% confidence interval, 1.7-1.8) than white infants.

CONCLUSIONS

Salmonellosis causes substantial infant morbidity and mortality; serotype heidelberg caused the most invasive infections. Infants with meningitis were younger than those with bacteremia or gastroenteritis. Research into risk factors for infection and invasive illness could inform prevention efforts.

Epidemiologic patterns of human Salmonella serotype diversity in the USA, 1996-2016

Although researchers have described numerous risk factors for salmonellosis and for infection with specific common serotypes, the drivers of Salmonella serotype diversity among human populations remain poorly understood. In this retrospective observational study, we partition records of serotyped non-typhoidal Salmonella isolates from human clinical specimens reported to CDC national surveillance by demographic, geographic and seasonal characteristics and adapt sample-based rarefaction methods from the field of community ecology to study how Salmonella serotype diversity varied within and among these populations in the USA during 1996–2016. We observed substantially higher serotype richness in children <2 years old than in older children and adults and steadily increasing richness with age among older adults. Whereas seasonal and regional variation in serotype diversity was highest among infants and young children, variation by specimen source was highest in adults. Our findings suggest that the risk for infection from uncommon serotypes is associated with host and environmental factors, particularly among infants, young children and older adults. These populations may have a higher proportion of illness acquired through environmental transmission pathways than published source attribution models estimate.

Agricultural production systems can serve as reservoir for human pathogens

Food-borne diseases are a threat to human health and can cause severe economic losses. Nowadays, in a growing and increasingly interconnected world, food-borne diseases need to be dealt with in a global manner. In order to tackle this issue, it is essential to consider all possible entry routes of human pathogens into the production chain. Besides the post-harvest handling of the fresh produce itself, also the prevention of contamination in livestock and agricultural soils are of particular importance. While the monitoring of human pathogens and intervening measures are relatively easy to apply in livestock and post-harvest, the investigation of the prevention strategies in crop fields is a challenging task. Furthermore, crop fields are interconnected with livestock via fertilizers and feed; therefore, a poor hygiene management can cause cross-contamination. In this review, we highlight the possible contamination of crop plants by bacterial human pathogens via the rhizosphere, their interaction with the plant and possible intervention strategies. Furthermore, we discuss critical issues and questions that are still open.

Salmonella Serotypes: A Novel Measure of Association with Foodborne Transmission

Most nontyphoidal Salmonella (NTS) illnesses in the United States are thought to be foodborne. However, transmission routes likely vary among the different serotypes. We developed a relative ranking of NTS serotypes according to the strength of their association with foodborne transmission. We used Laboratory-based Enteric Disease Surveillance data to estimate the proportion of infections for each Salmonella serotype reported from 1998 to 2015 and Foodborne Disease Outbreak Surveillance System data to calculate the proportion of foodborne outbreak-associated Salmonella illnesses caused by each serotype. We calculated the ratios of these proportions to create a foodborne relatedness (FBR) measure for each serotype. Of the top 20 serotypes, Saintpaul (2.14), Heidelberg (1.61), and Berta (1.48) had the highest FBR measures; Mississippi (0.01), Bareilly (0.13), and Paratyphi B variant L(+) tartrate(+) (0.20) had the lowest. The FBRs for the three most prevalent serotypes were 1.22 for Enteritidis, 0.77 for Typhimurium, and 1.16 for Newport. This method provides a quantitative approach to estimating the relative differences in the likelihood that an illness caused by a particular serotype was transmitted by food, which may aid in tailoring strategies to prevent Salmonella illnesses and guide future research into serotype-specific source attribution.

Preventing infection in the home

F undamental to controlling infection transmission in the home is the need to recognise it as an environment where all human activities occur, including food hygiene, hand hygiene and hygiene related to care of vulnerable groups. In recent years the concept of a risk assessment/risk reduction approach to hygiene has successfully controlled microbial risks in food and other manufacturing environments.

To deliver hygiene policy with real health benefits it is now accepted that a risk-based approach must also be developed for the home. The first step, hazard characterisation, involves identifying sites and surfaces where pathogens most frequently occur, and whether they are likely to be present in numbers that represent an infectious dose. A risk assessment is then made by considering this information together with an assessment of the probability of human exposure to the hazard. Risk reduction is achieved by application of a suitable hygiene procedure at the appropriate time.

Salmonella in the tropical household environment--Everyday, everywhere

OBJECTIVES

To determine the prevalence of Salmonella in the environment of case and control houses, and compare serovars isolated from cases and their houses.

METHODS

From 2005 to 2008, we tested samples from houses of 0-4 year old cases and community controls in Darwin and Palmerston for Salmonella. Case isolates were compared with environmental isolates. S. Ball and S. Urbana isolates were compared using Multiple Amplification of Phage Locus Typing (MAPLT) and Multiple-Locus Variable number of tandem repeat Analysis (MLVA).

RESULTS

Salmonella were found in 47/65 (72%) case houses and 18/29 (62%) control houses; these proportions were not significantly different. In 21/47 (45%) houses, case and environmental isolates (from animal faeces, soil and vacuums) were indistinguishable. Multiple serovars were isolated from 20 (31%) case and 6 (21%) control houses. All but one environmental isolate are known human pathogens in the Northern Territory (NT). Each of the four pairs of S. Ball and S. Urbana were indistinguishable.

CONCLUSIONS

Animal faeces were the most likely source of salmonellosis in cases. The similar prevalence of house isolates suggests that Salmonella is ubiquitous in this environment. The distinction of S. Ball and S. Urbana subtypes enabled linkage of human illness to environmental exposure. Environmental contamination with Salmonella is an important source of sporadic infection in children in the tropics.

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.

Multistate outbreak of Salmonella enterica serotype enteritidis infection associated with pet guinea pigs

Salmonella causes about one million illnesses annually in the United States. Although most infections result from foodborne exposures, animal contact is an important mode of transmission. We investigated a case of Salmonella enterica serotype Enteritidis (SE) sternal osteomyelitis in a previously healthy child who cared for two recently deceased guinea pigs (GPs). A case was defined as SE pulsed-field gel electrophoresis (PFGE) XbaI pattern JEGX01.0021, BlnI pattern JEGA26.0002 (outbreak strain) infection occurring during 2010 in a patient who reported GP exposure. To locate outbreak strain isolates, PulseNet and the US Department of Agriculture National Veterinary Service Laboratories (NVSL) databases were queried. Outbreak strain isolates underwent multilocus variable-number tandem repeat analysis (MLVA). Traceback and environmental investigations were conducted at homes, stores, and breeder or broker facilities. We detected 10 cases among residents of eight states and four NVSL GP outbreak strain isolates. One patient was hospitalized; none died. The median patient age was 9.5 (range, 1-61) years. Among 10 patients, two purchased GPs at independent stores, and three purchased GPs at different national retail chain (chain A) store locations; three were chain A employees and two reported GP exposures of unknown characterization. MLVA revealed four related patterns. Tracebacks identified four distributors and 92 sources supplying GPs to chain A, including one breeder potentially supplying GPs to all case-associated chain A stores. All environmental samples were Salmonella culture-negative. A definitive SE-contaminated environmental source was not identified. Because GPs can harbor Salmonella, consumers and pet industry personnel should be educated regarding risks.

Community-based infections and the potential role of common touch surfaces as vectors for the transmission of infectious agents in home and community settings

Community-based pathogens that can survive on common touch surfaces include those that can cause gastrointestinal, respiratory, and skin infections. Our hands play an obvious role in the transmission of many of these pathogens, but common touch surfaces are also part of the transmission equation. Traditionally, common touch surfaces have not been the main focus of cleaning and sanitation in household and community settings. Infectious disease continues to be of concern globally due in part to emergence of new pathogens, antibiotic-resistant organisms, and a growing immunocompromised community. As a result, it is important to prevent and minimize the infection risk in homes and in the community. Understanding the role of common touch surfaces should inform surface hygiene practices and these surfaces should be the subject of future intervention studies.

Epidemiological features and risk factors of Salmonella gastroenteritis in children resident in Ho Chi Minh City, Vietnam

Non-typhoidal Salmonella are an important but poorly characterized cause of paediatric diarrhoea in developing countries. We conducted a hospital-based case-control study in children aged <5 years in Ho Chi Minh City to define the epidemiology and examine risk factors associated with Salmonella diarrhoeal infections. From 1419 diarrhoea cases and 571 controls enrolled between 2009 and 2010, 77 (5·4%) diarrhoea cases were stool culture-positive for non-typhoidal Salmonella. Salmonella patients were more likely to be younger than controls (median age 10 and 12 months, respectively) [odds ratio (OR) 0·97; 95% confidence interval (CI) 0·94–0·99], to report a recent diarrhoeal contact (8·1% cases, 1·8% controls; OR 5·98, 95% CI 1·8–20·4) and to live in a household with >2 children (cases 20·8%, controls 10·2%; OR 2·32, 95% CI 1·2–4·7). Our findings indicate that Salmonella are an important cause of paediatric gastroenteritis in this setting and we suggest that transmission may occur through direct human contact in the home.

Clinical manifestations of nontyphoid salmonellosis in children younger than 2 years old--experiences of a tertiary hospital in southern Taiwan

BACKGROUND

Few published studies have explored the clinical manifestations of nontyphoid salmonellosis in children <2 years of age. The aim of this study was to investigate the clinical manifestations, microbiological features, complications, fecal excretion time, and responses to treatment in children <2 years of age with nontyphoid salmonellosis.

METHODS

Between January 2005 and December 2009, pediatric patients who were admitted to Kaohsiung Veterans General Hospital with positive cultures for nontyphoid Salmonella were enrolled. The following data were recorded: demographic, clinical, and microbiological features, underlying diseases, treatment regimen, complications, responses to treatment, and fecal excretion time. The clinical manifestations were compared between patients <2 years of age and patients >2 years of age.

RESULTS

Of a total 279 enrolled patients, 179 were >2 years of age. Compared with the patients who were ≥2 years of age, patients <2 years of age demonstrated a significantly higher incidence of bloody stool, mixed infection, extraintestinal infection, longer course of antibiotics, longer course of diarrhea after admission, and more days spent in the hospital. The rates of insusceptibility of nontyphoid Salmonella to ampicillin, chloramphenicol, trimethoprim/sulfamethoxazole, ceftriaxone, and ciprofloxacin in patients <2 years of age were 37.87%, 29.09%, 23.73%, 3.26%, and 2.25%, respectively. Younger patients were generally more susceptible to antibiotics than patients ≥2 years of age, although this result was not statistically significant.

CONCLUSION

The clinical manifestations of nontyphoid salmonellosis are more severe in younger children <2 years of age than older children. Local susceptibility patterns could serve as a guide for the prescription of antibiotics by clinicians.

Epidemiology, disease spectrum and economic burden of non-typhoidal Salmonella infections in Taiwan, 2006-2008

The purpose of this study was to understand the seasonal, geographical and clinical characteristics of Taiwanese patients hospitalized for non-typhoidal Salmonella (NTS) infections and their economic burden. Hospital data obtained from the Taiwan National Health Insurance (NHI) database between 2006 and 2008 were analysed. Infants had the highest annual incidence of 525 cases/100 000 person-years. Elderly patients aged >70 years had the highest in-hospital mortality rate (2·6%). Most (82·6%) gastroenteritis occurred in children aged <10 years. Septicaemia, pneumonia, arthritis and osteomyelitis occurred mainly in patients aged >50 years. A median medical cost for NTS-associated hospitalizations was higher for patients with septicaemia than for those with gastroenteritis. Seasonal variation of NTS-associated hospitalizations was correlated with temperature in different areas of Taiwan. In summary, infants had a high incidence of NTS-associated hospitalizations. However, the elderly had a higher in-hospital mortality rate and more invasive NTS infections than children.

Food safety and foodborne disease in 21st century homes

Over the past decade there has been a growing recognition of the involvement of the home in several public health and hygiene issues. Perhaps the best understood of these issues is the role of the home in the transmission and acquisition of foodborne disease. The incidence of foodborne disease is increasing globally. Although foodborne disease data collection systems often miss the mass of home-based outbreaks of sporadic infection, it is now accepted that many cases of foodborne illness occur as a result of improper food handling and preparation by consumers in their own kitchens. Some of the most compelling evidence has come from the international data on Salmonella species and Campylobacter species infections.By its very nature, the home is a multifunctional setting and this directly impacts upon the need for better food safety in the home. In particular, the growing population of elderly and other immnocompromised individuals living at home who are likely to be more vulnerable to the impact of foodborne disease is an important aspect to consider. In addition, some developed nations are currently undergoing a dramatic shift in healthcare delivery, resulting in millions of patients nursed at home. Other aspects of the home that are unique in terms of food safety are the use of the home as a daycare centre for preschool age children, the presence of domestic animals in the home and the use of the domestic kitchen for small-scale commercial catering operations. At the global level, domestic food safety issues for the 21st century include the continued globalization of the food supply, the impact of international travel and tourism, and the impact of foodborne disease on developing nations.A number of countries have launched national campaigns to reduce the burden of foodborne disease, including alerting consumers to the need to practice food safety at home. Home hygiene practice and consumer hygiene products are being refined and targeted to areas of risk, including preventing the onward transmission of foodborne illness via the inanimate environment. It has been said that food safety in the home is the last line of defense against foodborne disease, and it is likely that this will remain true for the global population in the foreseeable future.

Foodborne outbreak of Salmonella subspecies IV infections associated with contamination from bearded dragons

Approximately 1.4 million Salmonella infections and 400 deaths occur annually in the United States. Approximately 6% of human Salmonella cases are thought to be associated with reptiles; Salmonella enterica subspecies IV is primarily reptile-associated. During 1-4 December, 2009, three isolates of Salmonella IV 6,7:z4,z24:- with indistinguishable pulsed-field gel electrophoresis (PFGE) patterns were identified through Minnesota Department of Health laboratory-based surveillance. None of the three patients associated with the isolates reported reptile contact; however, all had attended the same potluck dinner. Dinner attendees were asked questions regarding illness history, foods they prepared for and consumed at the event, and pet ownership. Cases were defined as illness in a person who had eaten potluck food and subsequently experienced fever and diarrhoea (three or more loose stools in 24 h) or laboratory-confirmed infection with Salmonella IV matching the outbreak PFGE subtype. Nineteen days after the event, environmental samples were collected from a food preparer's house where two pet bearded dragons were kept. Sixty-six of 73 potluck food consumers were interviewed; 19 cases were identified; 18 persons reported illness but did not meet the case definition. Median incubation period was 19 h (range: 3-26 h). Median duration of illness was 5 days (range: 1-11 days). Consumption of gravy, prepared by the bearded dragons' asymptomatic owner, was associated with illness (16/32 exposed versus 1/12 unexposed; risk ratio: 6.0; exact P = 0.02). Salmonella Labadi was recovered from 10 samples, including from one bearded dragon, the bathroom door knob and sink drain, and the kitchen sink drain. The outbreak PFGE subtype of Salmonella subspecies IV was isolated from vacuum-cleaner bag contents. This foodborne outbreak probably resulted from environmental contamination from bearded dragons. Reptiles pose a community threat when food for public consumption is prepared in households with reptiles.

Distribution, diversity, and seasonality of waterborne salmonellae in a rural watershed

Salmonella outbreaks from contaminated water and nonanimal foods (e.g., produce) are increasingly reported. To address the environment as a potential source of pathogenic Salmonella, we investigated levels of salmonellae and the geographic and temporal variation of Salmonella serotypes from surface waters in a region of Georgia (United States) with a history of high salmonellosis case rates. Monthly water samples were collected from six stations in the Little River (Upper Suwannee Basin) for 12 months (April 2005 to April 2006). Salmonellae were enumerated using a three-step most-probable-number (MPN) assay. Salmonellae were detected in 57 of the 72 water samples collected (79.2%). Monthly Salmonella densities ranged from an MPN of 2.5 liter(-1) in April 2005 to 36.3 liter(-1) in August 2005; concentrations were significantly higher in the summer months compared to other seasons (P<0.05). Concentrations were not significantly different between stations. Levels of salmonellae were correlated with average daily watershed rainfall for the 1 and 2 days preceding each sample collection (r=0.77 and 0.68, respectively; P<0.005). Additionally, water temperature was also positively associated with total Salmonella levels (r=0.44; P<0.05). In total, 13 S. enterica serotypes were identified among 197 Salmonella isolates. Eighty (40.6%) were identified as S. enterica subsp. arizonae. Muenchen and Rubislaw were the most frequently identified serotypes of the remaining 117 isolates (28 and 26 isolates, respectively). Serotype diversity peaked in the summer, with 9 serotypes observed in August compared to only one serotype (S. enterica subsp. arizonae) observed in April (2005 and 2006) (P<0.05). Furthermore, all samples collected in August (6/6) contained multiple serotypes (two to five per sample). The results of this study suggest that Salmonella abundance and diversity in the environment vary temporally and are strongly influenced by seasonal precipitation and water temperature.

Evaluation of the risks of shedding Salmonellae and other potential pathogens by therapy dogs fed raw diets in Ontario and Alberta

Dogs that participate in animal-assisted interventions (AAIs), often called 'therapy dogs', commonly interact with humans whose immune systems are not functioning optimally. The advisability of feeding raw meat (including poultry) to these animals remains a highly contentious issue, in spite of increasing evidence that raw meat is frequently contaminated with Salmonella. We set out to determine if consuming raw meat influences the risk of therapy dogs shedding Salmonella and other pathogens. Two hundred healthy therapy dogs from Ontario and Alberta were enrolled. Between May 2005 and November 2006, fecal specimens were collected from each dog every 2 months for 1 year, along with a log of places visited, antimicrobial use within the home, dog health status and diet. Specimens were cultured for Salmonella, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), extended-spectrum cephalosporinase (ESC) Escherichia coli and Clostridium difficile. Forty (20%) of the dogs were reported to have been fed raw meat at some point during the year. The incidence rate of Salmonella shedding in the raw meat-fed dogs was 0.61 cases/dog-year, compared with 0.08 cases/dog-year in dogs that were not fed raw meat (P<0.001). Controlling for therapy dog group, the repeated measures, and pig ear consumption and diarrhoea in the 2 months prior to specimen submission, dogs that consumed raw meat were significantly more likely to test positive for Salmonella at least once during the year than dogs that did not eat raw meat [odds ratio (OR) 22.7; 95% confidence interval (CI) 3.1-58.8; P<0.001]. Specific Salmonella serovars were more common among dogs that consumed raw meat versus those that did not include S. Typhimurium, S. Heidelberg and S. Kentucky. Raw meat consumption was also significantly associated with shedding ESC E. coli (OR 17.2; 95% CI 9.4-32.3). No associations between C. difficile, MRSA or VRE and consumption of raw meat were detected. We recommend that dogs fed raw meat should be excluded from AAI programmes, particularly when the programmes involve interaction with humans at high risk of infection or adverse sequelae attributable to infection. Furthermore, although AAI dogs may not be representative of the general population of dogs, we also recommend that feeding of raw meat to dogs is to be avoided in homes where immunocompromised people live.

Epidemiologic attributes of invasive non-typhoidal Salmonella infections in Michigan, 1995–2001

OBJECTIVES

To determine: (1) the incidence of invasive salmonellosis, (2) the distribution of specific Salmonella serotypes associated with invasive disease, and (3) the role of demographic characteristics in invasive salmonellosis in Michigan.

DESIGN

We conducted a cross-sectional study using laboratory-confirmed cases of salmonellosis reported to the Michigan Department of Community Health between 1995 and 2001.

METHODS

Average annual incidences (AAIs) for invasive salmonellosis were computed, and Poisson regression analysis was used to model the association between demographic attributes and invasive salmonellosis.

RESULTS

Of 6797 cases of salmonellosis, 347 (5.1%) were characterized as invasive having an AAI of 0.5/100000. A covariate-adjusted Poisson model showed children aged <1 year to be at higher risk for invasive salmonellosis compared to adults aged 40-49 years (rate ratio (RR) 8.98, 95% confidence interval (CI) 5.69-14.17). No significant differences were found between males and females (RR 1.02, 95% CI 0.83-1.26), African-Americans and Caucasians (RR 0.95, 95% CI 0.64-1.42), and urban and rural residents (RR 0.98, 95% CI 0.76-1.26). Among the most common serotypes associated with invasive salmonellosis (Heidelberg, Typhimurium, and Enteritidis), Salmonella serotype Heidelberg had the highest blood invasiveness ratio (15.79/100).

CONCLUSIONS

Children aged <1 year, especially of minority groups, are at higher risk for invasive Salmonella infections. Invasive salmonellosis may be included in the differential diagnosis of acute bacterial infections in young children with positive stool cultures for Salmonella.

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.

Genetic and phenotypic variability among Salmonella enterica serovar Typhimurium isolates from California dairy cattle and humans

Fifty-six human and 24 adult dairy cattle isolates of Salmonella enterica serovar Typhimurium from a single county in California were compared using ribotyping, insertion sequence typing (IS200), pulsed-field gel electrophoresis, plasmid typing, phage typing, and antimicrobial resistance testing. The majority of the isolates fell into one of two groups which were phage types DT104 and DT193. Combining the information from all typing methods, a total of 45 different "clusters" were defined, with 35 of those including only a single isolate. The library of isolates had a high degree of variability, but antibiotic resistance and plasmid typing each defined single clusters in which human or bovine isolates predominated (chi2, P < 0.05).

Use of germicides in the home and the healthcare setting: is there a relationship between germicide use and antibiotic resistance?

BACKGROUND

The spread of antibiotic-resistant pathogens represents an increasing threat in healthcare facilities. Concern has been expressed that the use of surface disinfectants and antiseptics may select for antibiotic-resistant pathogens.

OBJECTIVE

To review the scientific literature on whether there is a link between use of germicides (ie, disinfectants and antiseptics) and bacterial resistance to antibiotics. In addition, we will review whether antibiotic-resistant bacteria exhibit altered susceptibility to germicides that are recommended for use as disinfectants or antiseptics.

DESIGN

A review of the appropriate scientific literature.

RESULTS

In the laboratory, it has been possible to develop bacterial mutants with reduced susceptibility to disinfectants and antiseptics that also demonstrate decreased susceptibility to antibiotics. However, the antibiotic resistance described was not clinically relevant because the test organism was rarely a human pathogen, the altered level of antimicrobial susceptibility was within achievable serum levels for the antibiotic, or the antibiotic tested was not clinically used to treat the study pathogen. Similarly, wild-type strains with reduced susceptibility to disinfectants (principally, quaternary ammonium compounds) and antiseptics (principally, triclosan) have been reported. However, because the concentration of disinfectants used in the healthcare setting greatly exceeds the concentration required to kill strains with reduced susceptibility to disinfectants, the clinical relevance of these observations is questionable.

CONCLUSION

To date, there is no evidence that using recommended antiseptics or disinfectants selects for antibiotic-resistant organisms in nature. Disinfectants and antiseptics should be used when there are scientific studies demonstrating benefit or when there is a strong theoretical rationale for using germicides.

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 Montevideo outbreak in military kennel dogs caused by contaminated commercial feed, which was only recognized through monitoring

A large outbreak of canine salmonellosis in military watch dogs due to Salmonella Montevideo and/or Salmonella Give was only recognized through a monitoring program, implemented by the military forces. In 51 out of 80 exposed dogs (63.8%) from four kennels Salmonella was isolated from fecal samples. The prevalence per sampling day ranged from 5.6 to 77.8%. Clinical disease with mild diarrhea but without fever appeared only in nine dogs (11.3% of study population, 16.9% of cases) from one kennel (***P < 0.001). Risk analysis identified "dog food A" (odds ratio 3.33 [1.12 < OR < 10.06] *P < 0.05) and "dog food C" (odds ratio 3.40 [1.07 < OR < 11.22] *P < 0.05), two commercial dehydrated dog feeds, as suspected infectious sources. Feeding "dog food C" alone or together with "dog food A" was significantly associated with clinical disease (***P < 0.001). S. Montevideo and S. Give with similar plasmid profiles and PFGE-restriction patterns were isolated from the suspected dog feeds and fecal samples. This outbreak demonstrates not only that Salmonella infections in dogs occur without clinical symptoms but also that large outbreaks occur after feeding dehydrated dog feeds. Especially in households with known risk group patients this finding demonstrates a particular risk for their owners, as they often live in close contact with their animals.

Risk factors for Salmonella Enteritidis and Typhimurium (DT104 and non-DT104) infections in The Netherlands: predominant roles for raw eggs in Enteritidis and sandboxes in Typhimurium infections

Since 1996 Salmonella Typhimurium DT104 salmonellosis has increased in The Netherlands. This prompted a case-control study of risk factors for salmonellosis to inform transmission routes for this phage type. Cases were laboratory-confirmed patients with a Salmonella infection and controls were selected from population registries by frequency matching for age, sex, degree of urbanization and season. Cases and controls received a questionnaire on risk factors. Of the 1171 cases, 573 (49%) responded: 245 S. Enteritidis and 232 S. Typhimurium cases (both DT104 and non-DT104), of which 58 were DT104. Of the 10250 controls, 3409 (33%) responded. Use of H2 antagonists [odds ratio (OR) 4.4, 95% CI 1.6-12.2] and proton pump inhibitors (OR 4.2, 95% CI 2.2-7.9), consumption of raw eggs (OR 3.1, 95% CI 1.3-7.4) and products containing raw eggs (OR 1.8, 95% CI 1.1-3.0) were associated with endemic S. Enteritidis infection. Risk factors for endemic S. Typhimurium infection were use of proton pump inhibitors (OR 8.3, 95% CI 4.3-15.9), occupational exposure to raw meat (OR 3.0, 95% CI 1.1-7.9), playing in a sandbox (for children aged 4-12 years) (OR 2.4, 95% CI 1.6-3.7), consumption of undercooked meat (OR 2.2, 95% CI 1.1-4.1) and use of antibiotics (OR 1.9, 95% CI 1.0-3.4). Use of proton pump inhibitors (OR 11.2, 95% CI 3.9-31.9) and playing in a sandbox (OR 4.4, 95% CI 1.8-10.7) were the only risk factors for S. Typhimurium DT104 salmonellosis. This study confirms known risk factors for salmonellosis. However, playing in a sandbox was a predominant new risk factor for S. Typhimurium salmonellosis in children [population attributable risk (PAR) 14%], and especially for S. Typhimurium DT104 (PAR 32%).

A recurring salmonellosis epidemic in New Zealand linked to contact with sheep

One strain of Salmonella Brandenburg began causing large numbers of human infections in New Zealand in 1998. We investigated the emergence of this strain using combined notification and laboratory data on human and animal disease and a case-control study. S. Brandenburg infection in humans was characterized by spring peaks and high rates in the southern half of the South Island. This epidemic pattern followed very closely that seen in sheep. The case-control study found that infection was significantly associated with occupational contact with sheep and having a household member who had occupational contact with sheep, during the 3 days prior to illness or interview. We conclude that S. Brandenburg has become established as a zoonotic disease in New Zealand. Preventing infection requires control of the epidemic in sheep through vaccination, changes in farm management practices, and promotion of hand washing and other precautions to protect farmers and their families.

Molecular epidemiologic surveillance of salmonellosis in Arkansas

OBJECTIVES

Salmonella serotype Newport and Salmonella serotype Typhimurium are the most commonly identified serotypes of Salmonella causing human disease in the state of Arkansas. The purpose of our study was to compare the results of standard and molecular epidemiologic methods of investigating human salmonellosis cases due to Salmonella serotype Newport and Salmonella serotype Typhimurium.

METHODS

All isolates of Salmonella serotype Newport and Salmonella serotype Typhimurium collected and submitted to the Arkansas Department of Health between July 1, 1997 and June 30, 1998 were gathered and underwent pulsed-field gel electrophoresis (PFGE). Patients from whom the isolates were collected were contacted and completed a questionnaire.

RESULTS

There were 84 patients from whom Salmonella serotype Newport was isolated and 83 from whom Salmonella serotype Typhimurium was isolated during the study period. In the 124 patients (74%) who completed the questionnaire, Salmonella serotype Newport was more likely to be the infecting agent in younger, white, and pet-owning patients (P < 0.05). The use of PFGE confirmed that approximately 20% of the organisms had genetic fingerprint patterns identical to those of at least one other individual in the state. One third of the patients from whom these isolates were obtained were linked by standard epidemiologic methods.

CONCLUSIONS

The use of PFGE on our state's most common isolates provides additional confirmation that despite being linked by time of onset and location of residence, the majority of the human salmonellosis cases in our region are still sporadic. Low-level, intermittent transmission of these organisms through environmental contamination and contact with asymptomatically infected individuals would be likely vehicles of transmission in our state. Molecular techniques are important in surveillance systems that investigate human salmonellosis. Eighty-one percent of the Salmonella serotype Newport and 92% of the Salmonella serotype Typhimurium cases that appeared to be outbreak-related based upon time of onset and location were actually found not to be outbreak-related by PFGE. Using techniques such as PFGE will allow for more focused evaluations of potential outbreaks and will save the already limited financial and human resources that would otherwise be spent on investigations that are not warranted.

Effect of antibacterial home cleaning and handwashing products on infectious disease symptoms: a randomized, double-blind trial

BACKGROUND

Despite the widespread household use of cleaning and personal hygiene products containing antibacterial ingredients, their effects on the incidence of infectious disease symptoms have not been studied.

OBJECTIVE

To evaluate the effect of antibacterial cleaning and handwashing products for consumers on the occurrence of infectious disease symptoms in households.

DESIGN

Randomized, double-blind clinical trial.

SETTING

Northern Manhattan inner-city neighborhood, New York.

PARTICIPANTS

238 primarily Hispanic households (1178 persons) that included at least one preschool-age child.

INTERVENTIONS

Households were randomly assigned to use either antibacterial or nonantibacterial products for general cleaning, laundry, and handwashing. All products were commercially available, but the packaging was blinded and the products were provided free to participants.

MEASUREMENTS

Hygiene practices and infectious disease symptoms were monitored by weekly telephone calls, monthly home visits, and quarterly interviews for 48 weeks.

RESULTS

Symptoms were primarily respiratory: During 26.2% (717 of 2736) of household-months, 23.3% (640 of 2737) of household-months, and 10.2% (278 of 2737) of household-months, one or more members of the household had a runny nose, cough, or sore throat, respectively. Fever was present during 11% (301 of 2737) of household-months, vomiting was present in 2.2% (61 of 2737), diarrhea was present in 2.5% (69 of 2737), and boils or conjunctivitis were present in 0.77% (21 of 2737). Differences between intervention and control groups were not significant for any symptoms (all unadjusted and adjusted relative risks included 1.0) or for numbers of symptoms (overall incidence density ratio, 0.96 [95% CI, 0.82 to 1.12]).

CONCLUSIONS

The tested antibacterial products did not reduce the risk for symptoms of viral infectious diseases in households that included essentially healthy persons. This does not preclude the potential contribution of these products to reducing symptoms of bacterial diseases in the home.

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.

Septicemic Salmonellosis in Two Cats Fed a Raw-Meat Diet

Salmonella gastroenteritis and septicemia were diagnosed in two cats presented for necropsy. Both cats resided in the same household and were fed a home-prepared, raw meat-based diet. Salmonella was isolated from multiple organs in both cats and from samples of raw beef incorporated into the diet fed to one of the cats. Subtyping of the bacterial isolates yielded Salmonella newport from one cat and from the diet it had been fed. This report provides evidence that the practice of feeding raw meat-based diets to domestic cats may result in clinical salmonellosis.

Models of antimicrobial resistance and foodborne illness: examining assumptions and practical applications

Antimicrobial resistance is an issue of increasing global concern. Several investigators have suggested that antibiotic use in food-producing animals is a major contributor to the increasing incidence of antimicrobial-resistant organisms causing illness in humans (F. J. Angulo, K. R. Johnson, R. V. Tauxe, and M. L. Cohen, Microb. Drug Res. 6:77-83, 2000; P. D. Fey, T. J. Safranek, M. E. Rupp, E. F. Dunne, R. Efrain, P. C. Iwen, P. A. Bradford, F. J. Angulo, and S. H. Hinrichs, N. Engl. J. Med. 342:1242-1249, 2000; S. A. McEwen and P. J. Fedorka-Cray, Commun. Infect. Dis. 34(Suppl. 3):S93-S106, 2002; D. L. Smith, A. D. Harris, J. A. Johnson, E. K. Silbergeld, and J. G. Morris, Jr., Proc. Natl. Acad. Sci. USA 99:6434-6439, 2002; D. G. White, S. Zhao, R. Sudler, S. Ayers, S. Friedman, S. Chen, P. F. McDermott, D. D. Wagner, and J. Meng, N. Engl. J. Med. 345:1147-1154, 2001; W. Witte, Science 279:996, 1998). In this paper, we discuss this and other assumptions relevant to a quantitative risk assessment model for salmonellosis in humans. We also discuss other important aspects of modeling food safety and food-associated antimicrobial resistance risk to humans. We suggest that the role of food-producing animals in the origin and transmission of antimicrobial resistance and "foodborne" pathogens has been overestimated and overemphasized in the scientific literature; consequently, nonfoodborne transmission, including pet-associated human cases, has been underemphasized. Much evidence exists for the potential contribution to infectious disease that may be of human or pet origin (that may contact humans through food but not be of a food origin). Risk analyses that do not acknowledge the potential for these sources of cross-contamination will understate the contribution that origin has in the realm of foodborne and food-associated diseases (e.g., Salmonella) and the resulting uncertainty levels in the food system, thus leading to biased inferences. We emphasize the importance of evaluating both the foodborne and nonfoodborne transmission risk for salmonellosis and outline the basics of an analytical modeling approach in food safety with examples to illustrate strengths and limitations in the modeling. Examples illustrate, on a simplistic level, how varying assumptions and other inputs can influence the output of food-associated quantitative risk models.

The survival and recovery of bacteria in vacuum cleaner dust

The possibility exists that environmental dust could be a source of gastro-intestinal infection in the domestic environment and that the causative microbes are collected during vacuum cleaning. This study examines the survival of total bacterial populations, Enterobacteriaceae and salmonella species in vacuum cleaner dust in vitro and in use. Total counts remain constant at around 10(6)-10(8) colony forming units (cfu) g-1 for at least 60 days. Enterobacteriaceae showed only a slight decline over the same period. Recovery of salmonellae artificially inoculated into vacuum dust was dose and time dependent: even relatively small inocula (< 100 cfu g-1) were recoverable more than one month after inoculation. Questionnaires and vacuum cleaner dust samples were received from 76 households. A significant association was found between total bacterial counts and whether the household was in a rural or urban situation and the number of people in the household. No association was found between total bacterial counts and the number of children in the household, the presence of pets, wearing shoes indoors, the makes, model and age of the vacuum cleaner, the type of dust collector or dust bag, how often the vacuum cleaner was used and the length of time between sample collection and microbiological testing. Salmonella species were isolated from vacuum cleaner dust from three of the 76 households although no factors could be identified linking the homes. This study shows that vacuum cleaners are effective collectors and reservoirs of microbial contamination and that these contaminants are able to survive for up to two months. Vacuum cleaner dust could thus be a useful indicator of environmental contamination in the home.

Home hygiene: a risk approach

The need to place "prevention through hygiene" at the core of strategies for infection prevention has been emphasised by recent events. Indications are that re-evaluation of current practice and the promotion of improved hygiene in the domestic setting could have a significant impact in reducing infectious disease. If the public are to play a part however they must be properly informed. Encouraging the concept of the home as a setting in which the whole range of activities occur, including food hygiene, personal hygiene and hygiene related to medical care, provides the opportunity for a rational approach to home hygiene based on risk assessment. In the home surfaces (including hand surfaces) and other sites play an important part in the transmission of infection, especially food-borne infections. From an assessment of the frequency of occurrence of pathogens and potential pathogens at reservoirs, disseminators and hand and food contact sites together with the potential for transfer within the home, the risks of exposure can be assessed. This can be used to develop a rational approach in which effective hygiene procedures involving cleaning and disinfection as appropriate are targeted at these sites to reduce risks of cross contamination. This approach is consistent with the view that good home hygiene is not about "getting rid of household germs" but about targeting hygiene measures appropriately to reduce exposure to germs and thereby prevent cross infection. In motivating change, education programmes must take account of concerns related to antimicrobial resistance, the environment and the "health" of the immune system.

Household contamination with Salmonella enterica

Household contamination with Salmonella enterica increases when occupational exposure exists (cattle farms with known salmonellosis in cattle, a salmonella research laboratory, or a veterinary clinic experiencing an outbreak of salmonellosis). Fifteen of 55 (27.2%) vacuum cleaner bags from households with occupational exposure to S. enterica were positive versus 1 of 24 (4.2%) without known exposure. Use of a carpet cleaner and several cleaners/disinfectants reduced, but failed to eliminate, S. enterica from artificially contaminated carpet.

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.

The role of the home environment in the transmission of infectious diseases

The purpose of this paper is to examine current health care literature (1980-2000) regarding the microbiology of the home environment, to summarize evidence of transmission within the home, and to assess effectiveness of cleaning practices and products. The home environment, particularly the kitchen and bathroom, serves as a reservoir of large numbers of microorganisms, particularly Enterobacteriacae, and infectious disease transmission has been demonstrated to occur in 6-60% of households in which one member is ill. Current food preparation and cleaning practices provide multiple opportunities for intra-household member spread. Routine cleaning is often sufficient, but in cases of household infection, may not adequately reduce environmental contamination. The effectiveness of disinfectants varies considerably and depends on how they are used as well as their intrinsic efficacy. The behavioral aspects of infection prevention in the home (e.g., foodhandling and cleaning practices) warrant increased public attention and education.

Enteric and foodborne disease in children: A review of the influence of food- and environment-related risk factors

Canadian statistics show that children from birth to four years of age are more likely to be reported with an infection from Campylobacter, Giardia, Salmonella and Shigella species, and verotoxigenic Escherichia coli than any other age group. A review of the Canadian and international literature, and an analysis of case and outbreak data suggest that the risk factors for infection in young children (ages birth to four years) are different from the risk factors for older children and adults. In children from birth to four years of age, infant formula, fast foods, snacks and candies have caused major outbreaks of enteric and foodborne diseases; however, the contamination of a child's environment or the presence of ill individuals in a household may be highly significant to disease expression. Contact with animals (including family pets) and contaminated surfaces, together with experimental touching and testing behaviours, are important routes of infection for infants and preschool children. Risk factors for enteric infections in children appear to be related, occasionally, to specific foods that are particularly attractive to all children (all age groups from infants up to and including elementary school-aged childen), to an infected person or pet in the same household, or to the contamination of a child's environment. Nonfood-related risk factors may be of particular significance in infection in infants and very young children. Contact with animals, particularly exotic pets and farm animals, or their environments should be considered to be a potential source of infection in children in situations in which there is an absence of other risk factors. The evidence presented in the current paper emphasizes the importance of personal and home hygiene practices in limiting children's exposure to enteric pathogens. Strict hand washing practices and restrictions on touching birds, reptiles and other animals at petting zoos or in nursery and primary school facilities are recommended to avoid widespread infection. Public health authorities should consider the development of guidelines on the provision of hand washing facilities and instruction notices in settings where the public may come into contact with farm or other animals in jurisdictions where such guidelines do not already exist.

Home hygiene practices and infectious disease symptoms among household members

Public health programs are generally targeted to communitywide, population-based prevention strategies, with little attention focused on the home environment as one potential source of transmission of infectious diseases. The purpose of this correlational prevalence survey was to describe the relationship between home hygiene practices and prevalence of infectious disease symptoms among household members. Three hundred and ninety-eight households with 1,662 members in an inner-city population (96.4% Hispanic) were surveyed to examine hygiene practices and determine the presence of transmission of infection, defined as the presence of the same symptom(s) in two or more household members for which at least one individual sought medical attention and received treatment. At least one individual in 78.6% of households reported symptoms of infection in the previous 30 days, and 37.9% of households met the definition of disease transmission. In univariate analyses, five factors were significantly associated with risk of household transmission, but in the logistic regression model, only use of communal laundry (p = 0.009) and lack of bleach use (p = 0.04) were significantly predictive of increased risk of transmission. This is the first comprehensive survey of home hygiene practices and the first study to identify a potential link between laundry and risk of disease transmission in homes. This potential link warrants further study in clinical trials.

Relationship between cross-contamination and the transmission of foodborne pathogens in the home

Environmental microbiologists have accumulated a substantial amount of information about the relationship between cross-contamination and the transmission of foodborne pathogens in the home. This information can be translated into guidelines for safe, effective hygienic practices in the home. Such guidelines cannot be mandated but should be strongly promoted via health and hygiene agencies to the general public. Establishing consensus-based, effective hygiene guidelines will benefit the community by reducing the risk of home-based infections such as foodborne disease and by lowering the associated healthcare costs.

Survival of Salmonella in bathrooms and toilets in domestic homes following salmonellosis

The survival and environmental spread of Salmonella bacteria from domestic toilets was examined in homes, where a family member had recently suffered an attack of salmonellosis. In four out of six households tested, Salmonella bacteria persisted in the biofilm material found under the recess of the toilet bowl rim which was difficult to remove with household toilet cleaners. In two homes Salmonella bacteria became incorporated into the scaly biofilm adhering to the toilet bowl surface below the water line. Salmonella enteritidis persisted in one toilet for 4 weeks after the diarrhoea had stopped, despite the use of cleaning fluids. Salmonellas were not isolated from normally dry areas such as, the toilet seat, the flush handle and door handle. Toilet seeding experiments were set up with Salmonella enteritidis PT4 to mimic environmental conditions associated with acute diarrhoea. Flushing the toilet resulted in contamination of the toilet seat and the toilet seat lid. In one out of three seedings, Salmonella bacteria were also isolated from an air sample taken immediately after flushing, indicating that airborne spread of the organism could contaminate surfaces in the bathroom. In the seeded toilet Salmonella bacteria were isolated from the biofilm in the toilet bowl below the waterline for up to 50 d after seeding, and also on one occasion from the bowl water. The results suggest that during diarrhoeal illness, there is considerable risk of spread of Salmonella infection to other family members via the environment, including contaminated hands and surfaces in the toilet area.