No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
An Outbreak of Salmonella Typhimurium 108/170 at a Privately Catered Barbeque at a Sydney Sports Club
Abstract
An outbreak of gastrointestinal illness was identified among attendees at a large community barbeque at a Sydney sports club on 30 January 2009. A retrospective cohort study was initiated, and attendees were identified through hospital emergency department gastroenteritis presentations, snowball recruitment through known cases, responders to linguistically specific press, and those returning to the venue the next week. A symptom and food history was collected from attendees, and stool samples were provided for microbiological investigation. An environmental investigation and trace back of implicated foods was also undertaken. Attendance estimates at the barbeque ranged from 100 to 180, and the food was prepared by a family that was not registered as a food business. Seventy one of the 87 attendees identified met the case definition. Thirty attendees (42%) had laboratory confirmed Salmonella Typhimurium phage-type 108/170, all with the same multilocus variable number of tandem repeat analysis typing. Burden of illness was high with 76% of cases seeking medical attention and 18% admitted to hospital. Microbiological evidence confirmed that a number of food items were contaminated with Salmonella Typhimurium 108/170, with the raw egg mayonnaise used in a Russian salad being the most likely primary food vehicle (adjusted odds ratio=10.3 [95% confidence interval 1.79-59.5]). Further, having Russian salad on the plate even if it was not consumed increased the relative risk of illness, thus suggesting that other food items may have been contaminated when they came into contact with it on the plate. This Salmonella outbreak highlighted the risks associated with the improper handling of food in private residences, which are then sold at a large public event.
... In NSW, S. Typhimurium outbreaks relating to food at sports activities were also identified: an outbreak among 35 attendees of a high-profile sports club was associated with a lamb meal supplied by an external caterer in 2014 [31] and another, larger outbreak occurred at a privately catered barbeque at a sports club in 2009 [32], where 71 cases had consumed the raw egg mayonnaise used in a Russian salad. This larger outbreak indicated a high burden of illness: 76% and 18% of the identified cases required medical attention and hospitalisation, respectively [32]. ...
... In NSW, S. Typhimurium outbreaks relating to food at sports activities were also identified: an outbreak among 35 attendees of a high-profile sports club was associated with a lamb meal supplied by an external caterer in 2014 [31] and another, larger outbreak occurred at a privately catered barbeque at a sports club in 2009 [32], where 71 cases had consumed the raw egg mayonnaise used in a Russian salad. This larger outbreak indicated a high burden of illness: 76% and 18% of the identified cases required medical attention and hospitalisation, respectively [32]. The authors noted that, since sport teams might be at high risk of foodborne illness arising from mass catering at training, events or functions, strict food-safety principles are needed, particularly for large-scale events [31]. ...
Non-typhoidal Salmonella is a major zoonotic pathogen that plays a significant role in foodborne human salmonellosis worldwide through the consumption of contaminated foods, particularly those of animal origin. Despite a considerable reduction in human salmonellosis outbreaks in developed countries, Australia is experiencing a continuous rise of such outbreaks in humans. This review of the literature highlights the reported non-typhoidal Salmonella outbreaks in humans as well as the occurrence of the pathogen in foods from animal sources throughout Australia. Non-typhoidal Salmonella infections from food animals are more often associated with at-risk people, such as immunocompromised and aged people or children. Although several animal-sourced foods were recognised as the catalysts for salmonellosis outbreaks in Australia, egg and egg-based products remained the most implicated foods in the reported outbreaks. This review further highlights the antimicrobial resistance trends of non-typhoidal Salmonella isolates at the human–food interface, with a focus on clinically important antimicrobials in humans, by collating evidence from previous investigations in Australia. The rise in antimicrobial-resistant Salmonella, especially to antimicrobials commonly prescribed to treat human salmonellosis, has become a significant global public health concern. However, the overall prevalence of antimicrobial resistance in Australia is considerably lower than in other parts of the world, particularly in terms of critically important antimicrobials for the treatment of human salmonellosis. The present review adds to our understanding of the global epidemiology of non-typhoidal Salmonella with emphasis on the past few decades in Australia.
... The higher rates of Salmonella, particularly S. Typhimurium, detected in the present study compared with those found in other parts of Australia and New Zealand may be attributable to the climatic conditions in different geographical areas, as well as to Salmonella infection status of birds and the effectiveness of cleaning and other hygiene and biosecurity measures [17]. S. Typhimurium has been the dominant serovar in recent human salmonellosis cases in Australia and has been frequently implicated in causing egg-borne human salmonellosis outbreaks, which is an increasing public health concern [18,19]. In WA, the reported number of human salmonellosis cases has increased dramatically compared with other Australian states, and S. Typhimurium was the major species responsible for most of the egg-linked outbreaks in WA [10]. ...
The aim of this study was to investigate the occurrence and distribution of Salmonella in commercial layer farming environments of 26 flocks belonging to seven egg businesses (free-range and barn-laid) in Western Australia (WA). Between November 2017 and June 2018, a total of 265 environmental samples of dust, feed, water, pooled feces, and boot swabs were tested for detection of Salmonella according to standard culture-based methods. Isolates were assayed for serovar and subtyped by multilocus sequence typing (MLST). Salmonella spp. were recovered from 35% (93/265) of all tested samples. Dust (53.8%, 28/52) and pooled fecal (54.5%, 18/33) samples provided the highest Salmonella recovery rates. Nine different Salmonella serovars were characterized across the positive (n = 93) environmental samples, of which S. Typhimurium (60/93, 64.5%) and S. Infantis (21/93, 22.5%) were the most prevalent. MLST revealed that all S. Typhimurium isolates were of sequence type ST-19. Microbiological screening of Salmonella was not routinely practiced in any of the surveyed egg businesses. Some of the egg businesses exhibited variable levels of compliance with basic biosecurity measures as well as high-risk egg handling practices. Egg businesses in WA should be encouraged to adopt a voluntary program of environmental sampling and verification testing for Salmonella. Such voluntary programs will aid in supporting solutions for the management of this pathogen in the human food chain.
... However, since that time, Australia has reported a significant increase in salmonellosis cases (Kirk et al., 2014). Salmonella Typhimurium has dominated this increase as well as being frequently implicated in causing foodborne outbreaks, especially those involving the use of raw eggs, causing particular concern for public health authorities (Stephens et al., 2007;Dyda et al., 2009;Reynolds et al., 2010;Jardine et al., 2011;Moffatt and Musto, 2013). We analyzed national data on foodborne disease outbreaks to examine trends in egg-associated salmonellosis outbreaks over time and by etiology. ...
Introduction:
Salmonellosis is a significant public health problem, with eggs frequently identified as a food vehicle during outbreak investigations. Salmonella enterica serovar Typhimurium and Salmonella enterica serovar Enteritidis are the two most frequently identified causes of egg-associated disease in industrialized countries. In Australia, a comprehensive review of egg-associated outbreaks has not been previously undertaken.
Methods:
Using a national register of foodborne outbreaks, we undertook a descriptive review of egg-associated outbreaks between 2001 and 2011. Included in our review was additional detail from the findings of trace back investigations conducted to the farm level. Evidence classifications were developed and applied to each outbreak based on descriptive and analytical epidemiology, food safety investigations, and microbiological testing of clinical, food, and trace back-derived samples.
Results:
Over the study period, the proportion of foodborne Salmonella outbreaks linked to eggs increased significantly (p < 0.001). In total, 166 outbreaks were identified, with 90% caused by Salmonella Typhimurium. The majority of outbreaks were linked to commercial food providers, with raw egg use the major contributing factor. These events resulted in more than 3200 cases, more than 650 hospitalizations, and at least 4 deaths. Fifty-four percent of investigations used analytical epidemiology, food microbiology, and trace back microbiology to demonstrate links between human illness and eggs. Trace back investigations identified S. enterica indistinguishable from outbreak-associated clinical or food samples on 50% of sampled egg farms.
Conclusion:
Effective control of egg-associated salmonellosis remains a challenge in Australia, with Salmonella Typhimurium dominating as the causative serotype in outbreak events. Although outbreaks predominantly occur in the settings of restaurants, the high recovery rate of indistinguishable Salmonella on epidemiologically implicated egg farms suggests that further efforts to minimize infection pressure at the primary production level are needed in Australia.
... There are several possibilities for the source of the Salmonella contamination in this outbreak. Mayonnaise is a well-recognised vehicle of contamination when raw egg is used as an ingredient [8][9][10][11][12]. However, in this outbreak all cold dishes and salads were made from commercially prepared ingredients. ...
An outbreak of salmonellosis in the summer of 2010 after a wedding party in Bavaria, Germany, was investigated, to identify vehicles and source of the outbreak and any flaws in food safety procedures. A cohort study targeting all wedding participants was carried out in addition to laboratory and environmental investigations. The overall attack rate was 59% (52/88). A group of buffet dishes containing mayonnaise was associated with the highest relative risk: 6.6 (95% CI: 1.7-25.0). Subtyping of a subset of Salmonella isolates cultured from stool samples from wedding participants and catering staff and from food samples showed the isolates to be indistinguishable (S. Enteritidis, lyso-type 4/6, ribotype 3). European laws require food business operators to establish and implement food safety procedures. Investigation of the practices of the catering company revealed a lack of staff training and the absence of records of a food safety concept. Non-edible flower decorations in cold dishes were identified as a potential source of secondary contamination because their cultivation and processing are not subject to the food safety regulations minimising the risk of contamination of crops intended for human consumption. The outbreak demonstrated the importance of staff training and food safety concepts to identify and mitigate hazards to food safety.
The trends toward healthy living, vegetarianism, and busy schedules have increased salad popularity. Salads are usually consumed raw without any thermal treatment, and therefore, without proper care they can become major vehicles for foodborne illness outbreaks. This review examines the microbial quality of 'dressed' salads which contain two or more vegetables/fruits and salad dressings. The possible sources of ingredient contamination, recorded illnesses/outbreaks, and overall microbial quality observed worldwide, besides the antimicrobial treatments available are discussed in detail. Noroviruses were most frequently implicated in outbreaks. Salad dressings usually play a positive role in influencing microbial quality. However, this depends on several factors like the type of contaminating microorganism, storage temperature, dressing pH and ingredients, plus the type of salad vegetable. Very limited literature exists on antimicrobial treatments that can be used successfully with salad dressings and 'dressed' salads. The challenge with antimicrobial treatments is to find ones sufficiently broad in spectrum, compatible with produce flavour which can be applied at competitive cost. It is evident that renewed emphasis on prevention of produce contamination at the producer, processor, wholesale and retail levels plus enhanced hygiene vigilance at foodservice will have a major impact on reducing the risk of foodborne illnesses from salads.
Nontyphoidal salmonellae are among the most prevalent foodborne pathogens causing gastrointestinal infections worldwide. A high number of cases and outbreaks of salmonellosis are associated with the consumption of eggs and egg products, and several of these occur at the household level. The aim of the current study is to critically evaluate the current status of knowledge on Salmonella in eggs from a consumer's perspective, analyzing the hazard occurrence and the good practices that should be applied to reduce salmonellosis risk. Following a HACCP (Hazard Analysis and Critical Control Point) based approach, some steps along the food journey were identified as Critical Consumer Handling (CCH)-steps in which consumers, through their behavior or choice, can significantly reduce the level of Salmonella in eggs and egg products. From shopping/collecting to consumption, each of these steps is discussed in this review to provide an evidence-based overview of risk factors of human salmonellosis related to egg consumption. The main message to consumers is to choose Salmonella-free eggs (those that some official entity or producer guarantees that does not contain Salmonella), when available, especially for dishes that are not fully heat treated. Second, as guaranteed Salmonella-free eggs are only available in a few countries, refrigerated storage from the point of collection and proper cooking will significantly reduce the risk of salmonellosis. This will require a revision of the actual recommendations/regulations, as not all ensure that eggs are maintained at temperatures that prevent growth of Salmonella from collection until the time of purchasing.
Salmonella is one of the most common causes of foodborne disease worldwide. It also generates negative economic impacts due to surveillance investigation, and illness treatment and prevention. Salmonellosis is a zoonotic infection caused by Salmonella; for example, S. Enterica causes gastroenteritis, typhoid fever and bacteremia. Transmission is by the fecaloral route whereby the intestinal contents of an infected animal are ingested with food or water. Human carriers are generally less important than animals in transmission of Salmonella strains. A period of temperature abuse which allows the Salmonella spp. to grow in food and/or inadequate or absent final heat treatment are common factors contributing to outbreaks. Meat, poultry, egg, dairy products, and fruits and vegetables are primary transmission vehicles; they may be undercooked, allowing the Salmonella strains to survive, or they may cross-contaminate other foods consumed without further cooking. Crosscontamination can occur through direct contact or indirectly via contaminated kitchen equipment and utensils. This chapter is a review of the role foods play in Salmonella infections and provides an overview of the main food chain- associated Salmonella risks.
This report describes the investigation and public health response to a large point-source outbreak of salmonellosis in Sydney, Australia. The case-series investigation involved telephone interviews with 283 cases or their guardians and active surveillance through hospitals, general practitioners, laboratories and the public health network. In this outbreak 319 cases of gastroenteritis were identified, of which 221 cases (69%) presented to a hospital emergency department and 136 (43%) required hospital admission. This outbreak was unique in its scale and severity and the surge capacity of hospital emergency departments was stretched. It highlights that foodborne illness outbreaks can cause substantial preventable morbidity and resultant health service burden, requiring close attention to regulatory and non-regulatory interventions.
In April 2000, we investigated an outbreak of gastroenteritis amongst attendees of a local community dinner in a Perth suburb. Of the 98 people interviewed (response rate 98%), 53 reported gastrointestinal symptoms (attack rate 54%). Faecal cultures from 11 cases, 2 food preparers, 1 waitress and leftover mock ice-cream dessert grew Salmonella Typhimurium PT135. Of the 3 food handlers, one was asymptomatic, another gave an unclear history of onset of illness and the waitress claimed illness onset 9 days after the dinner. A cohort study implicated fruit salad (RR 1.64 [95% CI: 1.05-2.58], p=0.017) and/or mock ice-cream dessert (RR 1.78 [95% CI: 0.91-3.52], p=0.045). Eggs used to make the mock ice-cream dessert were supplied directly from the producer who used inappropriate shell cleaning methods. The method of preparation of the dessert encouraged contamination. Salmonella species were not isolated in poultry faecal samples collected from the implicated egg farm. The cause of this outbreak was almost certainly the ice-cream dessert with contamination most likely resulting either from the eggs used to make the dessert or one or both of the food preparers, coupled with inadequate cooking of the dessert. Eggs used in preparing food for mass consumption should be sourced from distributors with approved cleaning procedures. Furthermore, pasteurised egg products or egg pulp should be used in the preparation of uncooked or minimally cooked dishes.
Poor food handling practices in the home are a likely cause of gastroenteritis. This study examined how often reported practices in Australian homes met public health food safety recommendations. During 1998 in Melbourne, Australia, food handling and food storage questionnaires were completed by an adult member in 524 and 515 families, respectively. Each family consisted of at least two adults and two children. Respondents were surveyed regarding washing of hands, cutting boards, and fresh produce; use of kitchen cloths; egg storage; where cooked foods were cooled; the duration before refrigeration of cooked foods; where food types were positioned in the refrigerator; and the method of thawing chicken. Nearly every household reported handling food in a way that could cause food to become contaminated. Overall, 99.0% of respondents reported some form of mishandling, which encompassed 70.3% who handled food preparation surfaces poorly, 46.6% who did not wash their hands appropriately or in a timely manner, 41.7% who mishandled raw foods, and 70.1% who mishandled cooked foods. Food was inappropriately located in the refrigerator by 81.2%, and chicken was thawed using unsafe means by 76.3% of respondents. People preparing food in the home need to be reminded of the increased risk of disease that can arise from poor food handling practices.
In a climate of concern over bioterrorism threats and emergent diseases, public health authorities are trialling more timely surveillance systems. The 2003 Rugby World Cup (RWC) provided an opportunity to test the viability of a near real-time syndromic surveillance system in metropolitan Sydney, Australia. We describe the development and early results of this largely automated system that used data routinely collected in Emergency Departments (EDs).
Twelve of 49 EDs in the Sydney metropolitan area automatically transmitted surveillance data from their existing information systems to a central database in near real-time. Information captured for each ED visit included patient demographic details, presenting problem and nursing assessment entered as free-text at triage time, physician-assigned provisional diagnosis codes, and status at departure from the ED. Both diagnoses from the EDs and triage text were used to assign syndrome categories. The text information was automatically classified into one or more of 26 syndrome categories using automated "naïve Bayes" text categorisation techniques. Automated processes were used to analyse both diagnosis and free text-based syndrome data and to produce web-based statistical summaries for daily review. An adjusted cumulative sum (cusum) was used to assess the statistical significance of trends.
During the RWC the system did not identify any major public health threats associated with the tournament, mass gatherings or the influx of visitors. This was consistent with evidence from other sources, although two known outbreaks were already in progress before the tournament. Limited baseline in early monitoring prevented the system from automatically identifying these ongoing outbreaks. Data capture was invisible to clinical staff in EDs and did not add to their workload.
We have demonstrated the feasibility and potential utility of syndromic surveillance using routinely collected data from ED information systems. Key features of our system are its nil impact on clinical staff, and its use of statistical methods to assign syndrome categories based on clinical free text information. The system is ongoing, and has expanded to cover 30 EDs. Results of formal evaluations of both the technical efficiency and the public health impacts of the system will be described subsequently.
This report describes one of the largest egg-associated outbreaks of foodborne illness in Australia for many years. Between June and December 2005, five outbreaks of Salmonella Typhimurium phage type 135 were identified in Tasmania, leading to 125 laboratory-confirmed cases. Public health investigations included case and food handler interviews, cohort studies, environmental health investigations of food businesses, microbiological testing, traceback, and inspections and drag swabbing of an egg farm. These investigations enabled identification of foods containing raw egg or foods contaminated through inadequate food handling and/or storage procedures as possible vehicles for infection. A particular poultry farm was reported as the common source of eggs. Interventions targeting the general public and food handlers to promote better handling of egg products, and advice to egg producers regarding harm minimisation strategies led to the series of outbreaks being brought under control.
Salmonella enterica serovar Typhimurium (S. Typhimurium) is the commonest pathogen causing food-borne disease among humans and animals in Australia. A multiplex PCR-based reverse line blot (mPCR/RLB) system was developed to rapidly identify S. Typhimurium phage types and strains within them. The system comprised 32 biotin-labelled primer sets and 38 amino-labelled probes, based on sequences that were either phage-type-related or derived from temperate phages ST64B, P22, Gifsy-1 or Gifsy-2. The system was developed and evaluated using 168 S. Typhimurium isolates, representing 46 phage types. RLB patterns, based on a combination of positive hybridization and grading of signal intensities, validated by sequencing, differentiated S. Typhimurium isolates into 102 types. Some clusters contained isolates belonging to a single phage type while others contained isolates belonging to more than one. Most phage types exhibited at least two RLB profiles. The feasibility of this system was evaluated during investigations of three outbreaks, due to two different phage types. Within each outbreak, isolates showed identical RLB patterns, whereas sporadic isolates of corresponding phage types showed various patterns. The mPCR/RLB system was compared with multilocus variable-number tandem-repeat analysis (MLVA). The two methods demonstrated similar discriminatory abilities. Based on these preliminary results, the mPCR/RLB system is a promising tool for molecular identification of most common S. Typhimurium phage types. It could be used as an alternative to, or in conjunction with, MLVA for rapid strain typing during outbreaks.
In 2009, OzFoodNet sites reported 27,037 notifications of 9 diseases or conditions that are commonly transmitted by food. The most frequently notified infections were Campylobacter (15,973 notifications) and Salmonella (9,533 notifications). Public health authorities provided complete serotype and phage type information on 92% of all Salmonella infections in 2009. The most common Salmonella serotype notified in Australia during 2009 was Salmonella Typhimurium, and the most common phage type was S. Typhimurium 170/108. During 2009, OzFoodNet sites reported 1,820 outbreaks of gastrointestinal illness, which affected 36,426 people and resulted in 1240 people being hospitalised. There were 118 deaths during these outbreaks. The majority (82%, 1496/1820) of outbreaks were due to person-to-person spread, 9% (163/1820) were suspected or confirmed to have been transmitted by contaminated food and 9% (161/1820) were due to either waterborne transmission or outbreaks with an unknown mode of transmission. Foodborne outbreaks affected 2679 persons including 342 hospitalisations. Eight deaths were reported during these foodborne outbreaks. Salmonella was the most common aetiological agent in foodborne outbreaks and restaurants were the most common setting where foods were prepared. Eighteen outbreaks were related to dishes containing raw or undercooked eggs; the majority (n=14) due to various phage types of S. Typhimurium. This report summarises the incidence of disease potentially transmitted by food in Australia and details outbreaks associated with various food vehicles in 2009. These data assist agencies to identify emerging sources of disease, develop food safety policies, and prevent foodborne illness.
In 2007, OzFoodNet sites reported 27,332 notifications of 8 diseases or conditions that are commonly transmitted by food. The most frequently notified infections were Campylobacter (16,984 notifications) and Salmonella (9,484 notifications). Public health authorities provided complete serotype and phage type information on 96% of all Salmonella infections in 2007. The most common Salmonella serotype notified in Australia during 2007 was Salmonella Typhimurium, and the most common phage type was Salmonella Typhimurium 135. During 2007, OzFoodNet sites reported 1,882 outbreaks of gastrointestinal illness; the majority of these were spread person to person but included those transmitted by contaminated food. In total, these outbreaks affected 37,474 people and resulted in 1,034 people being admitted to hospital. During these outbreaks there were 114 deaths reported. Food was suspected or confirmed as the mode of transmission for 149 of these outbreaks, which affected 2,290 persons, hospitalised 266 persons and 5 deaths were reported during these outbreaks. For these foodborne outbreaks, S. Typhimurium was the most common aetiological agent and restaurants were the most common setting where foods were prepared. Twenty-four of these foodborne outbreaks were related to the consumption of eggs; the majority (n = 22) of these outbreaks were due to various phage types of S. Typhimurium. This report summarises the incidence of disease potentially transmitted by food in Australia and details outbreaks associated with various food vehicles in 2007. These data assist agencies to identify emerging disease, develop food safety policies, and prevent foodborne illness.
Large egg-associated outbreaks of Salmonella Typhimurium 135 (STm135) that were associated with inadequate food safety practices but also linked to a common poultry farm occurred in Tasmania in 2005. A series of public health interventions were implemented to prevent further occurrences but 2 more egg-associated outbreaks in Tasmania in March 2007 and January 2008 led to a further 66 cases of STm135. This report describes these outbreaks and their links to the common source associated with the outbreaks in 2005.
The authors report a cluster investigation of four notifications of Salmonella Typhimurium infection amongst children under five years of age within defined geographical area in southwest Brisbane. Eggs purchased from a local supplier who did not comply with recommended cleaning procedures for eggs may have been the source of this outbreak. (non-author abstract)
The multiple-locus variable-number tandem-repeats analysis (MLVA) method is currently being used as the primary typing tool for Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) isolates in our laboratory. Our published initial MLVA was performed using a single fluorescent dye and the different patterns were assigned from gel images. Here we present a new and significantly improved assay using multiple dye colors, enhanced PCR multiplexing and the introduction of two new loci for better adaptation to capillary electrophoresis with increased speed. The different MLVA patterns are now based on allele sizes entered as character values, thus removing the uncertainties introduced when analyzing band patterns from gel images. We additionally propose an easy numbering scheme for the identification of separate isolates that will facilitate exchange of typing data. A total of 106 human, bird, animal and food isolates of S. Typhimurium, including 16 with definite type (DT) 104, were used for the development of the improved MLVA. The method is based on capillary separation of multiplexed PCR products from five VNTR loci in the S. Typhimurium genome labeled with multiple fluorescent dyes. The different alleles at each locus were then assigned allele numbers, which were used for strain comparison.
An outbreak of Salmonella Typhimurium phage type 44 at a rural boarding school in Victoria
- Williams S J Fielding
- Gregory Je K Sturge
- Rowe S S Poznanski
Williams S, Fielding J, Gregory JE, Sturge K, Rowe S, Poznanski S, and Vally H. An outbreak of Salmonella Typhimurium phage type 44 at a rural boarding school in Victoria. Victorian Infect Dis Bull 2009;12:2–6.