A large outbreak of Salmonella enteritidis phage type 4 associated with eggs from overseas.

In February 1989 the largest reported outbreak to date in the United Kingdom of Salmonella enteritidis phage type 4 (PT4) infection occurred following a wedding reception at a hotel. One hundred and seventy-three people met the case definition of illness of whom 118 had the organism isolated from their stools. A further 17 were found to be S. enteritidis PT4 positive, but were asymptomatic. Lightly-cooked, egg-based sauces were the epidemiologically proven vehicles of infection. Investigations showed this outbreak to be the first to implicate imported European eggs as the source of infection. An unusual feature of this outbreak was a reported incubation period of less than 3 h for some of the confirmed cases of salmonellosis.     

A nosocomial outbreak of Salmonella enteritidis associated with lyophilized enteral nutrition

Outbreaks of Salmonella spp. gastro-enteritis in hospitals are of concern because of the increased susceptibility of patients and associated high morbidity. This study is a report of a nosocomial outbreak of Salmonella enteritidis associated with enteral nutrition. In December 1999, one sample of enteral feed tested positive for S. enteritidis. During the subsequent 6 weeks, eight cases of nosocomial salmonellosis occurred. Patients involved in the outbreak were aged 19-79 years (median = 36.5), and salmonella was isolated from the blood of two patients. All patients were receiving enteral nutrition at the time and all had diarrhoea. Three patients died. All 13 employees of the Nutrition Department were asymptomatic and their stool samples were negative. Environmental and water samples were also negative. The diet, however, contained lyophilized egg albumin. Molecular typing showed that the isolates of seven patients were indistinguishable from the one obtained from the enteral diet. It was thought that the nosocomial salmonellosis probably occurred due to the use of a commercial lyophilized diet. Another method of processing diets may be necessary to ensure patient safety.     

Large outbreak of Salmonella enteritidis PT8 in Portsmouth, UK, associated with a restaurant

Seventy-five individuals with Salmonella infection were identified in the Portsmouth area during August and September 2009, predominantly Salmonella Enteritidis phage type 8. Five patients were admitted to hospital. A case-case comparison study showed that a local restaurant was the most likely source of the infection with a risk of illness among its customers 25-fold higher than that of those who did not attend the restaurant. A case-control study conducted to investigate specific risk factors for infection at the restaurant showed that eating salad was associated with a threefold increase in probability of illness. Changing from using ready washed lettuces to lettuces requiring washing and not adhering strictly to the 48 hours exclusion policy for food handlers with diarrhoea were likely to have contributed to the initiation and propagation of this outbreak. Possibilities for cross-contamination and environmental contamination were identified in the restaurant.     

Two outbreaks of Salmonella enteritidis phage type 4 infection associated with the consumption of fresh shell-egg products

In 1988 there were two outbreaks of infection with Salmonella enteritidis phage type 4 in adjacent local authorities. The first affected 18 of 75 helpers and guests who attended a private function. Investigations revealed that home-made vanilla ice-cream containing uncooked eggs was the vehicle of infection and the causative organism was identified at the premises of the egg producer. The second affected 84 of 422 delegates attending a conference dinner, and 12 of 50 hotel staff at risk. A dessert made with lightly-cooked egg yolk and raw egg white was associated with infection, and the epidemic strain was cultured from the shell of an egg and an environmental sample from the producer's farm. It is of interest that one outbreak involved free-range and one battery-produced eggs, and that in one the vehicle was prepared at home and in the other in commercial premises. In neither incident was any deficiency in standards of egg production or catering practice discovered.     

A comparison of Salmonella enteritidis phage types from egg-associated outbreaks and implicated laying flocks.

Infections due to Salmonella enteritidis are increasing worldwide. In the United States, between 1985 and 1989, 78% of the S. enteritidis outbreaks in which a food vehicle was identified implicated a food containing raw or lightly cooked shell eggs. Under a US Department of Agriculture regulation published in 1990, eggs implicated in human food-borne S. enteritidis outbreaks were traced back to the source flock. The flock environment and the internal organs of a sample of hens were tested for S. enteritidis. We compared the S. enteritidis phage types of isolates from 18 human, egg-associated outbreaks and the 15 flocks implicated through traceback of these outbreaks. The predominant human outbreak phage type was recovered from the environment in 100% of implicated flocks and from the internal organs of hens in 88% of implicated flocks we tested. The results support the use of phage typing as a tool to identify flocks involved in human S. enteritidis outbreaks.     

Hospital outbreak of Salmonella virchow possibly associated with a food handler

A foodborne outbreak of salmonella infection at a private hospital in London in 1994 was found to be associated with eating turkey sandwiches prepared by a food handler. One patient, nine staff, and a foodhandler's baby were confirmed to have Salmonella enterica serotype virchow, phage type 26 infection. The attack rate was estimated to be 5% among the approximately 200 patients and staff at risk. A food handler reportedly became ill days after, but her baby days before, the first hospital case. Although it appeared to be a single outbreak, antibiogram analysis, supplemented by plasmid profile typing, demonstrated that there were two strains of S. virchow involved, one with resistance to sulphonamides and trimethoprim and a second sensitive to these antimicrobial drugs. Mother and child had different strains. The investigation demonstrated the importance of full phenotypic characterization of putative outbreak strains including antimicrobial susceptibility testing.Outbreaks of foodborne infection in hospitals are preventable and are associated with high attack rates and disruption of services. There is a need for good infection control policies and training of all staff involved in patient care as well as in catering services. Consultants in Communicable Disease (CCDCs) should include private hospitals in their outbreak control plans. Good working relations between Infection Control Doctors (ICDs) in the private health sector and their local CCDCs are important if outbreaks are to be properly investigated.     

Antimicrobial susceptibility and phage types of Salmonella enteritidis strains isolated in the Lublin area

The study aimed at specifying the value of two traditional methods of typing, using the collection of 241 strains of Salmonella Enteritidis isolated from people and animals in the Lublin area in 1994-1995 from the occasional cases of infections. There were 8 phage types identified among the examined strains. Phage types PT 6 (40.24% of strains) and PT 7 (29.46%) were the most numerous ones. Salmonella Enteritidis was numbered among 38 profiles on the basis of the analysis of resistance to 15 antimicrobial agents. It was found that nitrofurantoin had the lowest efficacy in vitro in relation to the examined collection of Salmonella isolates. High percentage of strains were characterized by lack of susceptibility to streptomycin, neomycin, cefixime, tetracycline and canamycine. While analyzing the profiles of resistance to chemiotherapeutics and the expression of phage type of the examined strains it was observed that only 14.1% of all strains showing resistance to nitrofurantoin represented at the same time phage type PT 6, whereas 10.8% of strains belonging to the same resistance profile indicated PT 7 phage type. In correlated analysis of resistance to chemiotherapeutics and phage type expression of the examined collection of 241 isolates of Salmonella Enteritidis, 18.3% of strains showed distinct and unique set of these two features, which can be used in epidemiological investigations for the preliminary characterization of the bacterial population.     

Molecular epidemiology of Salmonella enteritidis phage type 1b and 6a isolates in Portugal

Salmonella enterica serotype Enteritidis is an important serovar comprising 76 % of Salmonella isolates in Portugal in 2001. For better understand the epidemiology of salmonellosis, a total of 47 isolates of S. Enteritidis phage type (PT) 1b and 6a were analysed by pulsed-field gel electrophoresis (PFGE) and genomic DNA was subjected to macro restriction with XbaI. For PT 1b isolates, only three different patterns were observed, and PT6a showed a total of 10 digestion patterns. Curiously, the main pattern among PT1b isolates seams quite similar to main pattern of PT6a isolates, but when the two patterns were analysed with Bionumerics, we observed that they exhibited some differences. It was concluded that, in 2001, there was one predominant pattern for PT1b and PT6a and, possibly, we were in presence of clonal strains that exists all over the country.     

A statewide outbreak of Salmonella bovismorbificans phage type 32 infection in Queensland.

Between 30 May and 1 June 2001, 10 cases of Salmonella Bovismorbificans infection were reported to Public Health Services, Queensland Health. Investigations included enhanced surveillance, case interviews, a matched case control study, environmental audit and microbiological testing of faecal isolates (phage typing) and implicated food products. Forty-one cases of S. Bovismorbificans infection were detected, 36 cases were phage type 32. A matched case control study identified that illness was associated with consumption of food from 15 outlets of a fast food chain, Company A (matched odds ratio [MOR] 17.5, 95% CI 2.0-657.3, p = 0.004) and consumption of a particular product, Product X (MOR undefined, p < 0.001) in the week before onset of illness. Manufacturers of Product X ingredients were audited. Deficiencies were identified in equipment cleansing at the salad mixture processing plant (Manufacturer M). A swab of food residue behind the cutting wheel rim of the lettuce shredder was positive for S. Bovismorbificans phage type 32. This appears to be the first reported Australian outbreak of salmonellosis associated with a lettuce product. The investigations suggest that inadequate maintenance of cutting equipment to prepare lettuce ingredients for Product X by Manufacturer M was a key factor in this statewide outbreak. The statewide nature of this outbreak demonstrates the role of timely serovar identification of Salmonella isolates by a reference laboratory as an aid to outbreak identification, and the importance of adherence to appropriate food safety procedures in the manufacture and preparation of mass produced food items for the public.     

A national outbreak of multi-resistant Salmonella enterica serovar Typhimurium definitive phage type (DT) 104 associated with consumption of lettuce

Between 1 August and 15 September 2000, 361 cases of Salmonella enterica serotype Typhimurium definitive phage type (DT) 104, resistant to ampicillin, chloramphenicol, streptomycin, sulphonamides, spectinomycin and tetracycline (R-type ACSSuSpT), were identified in England and Wales residents. Molecular typing of 258 isolates of S. Typhimurium DT104 R-type ACSSuSpT showed that, although isolates were indistinguishable by pulsed-field gel electrophoresis, 67% (174/258) were characterized by a particular plasmid profile. A statistically significant association between illness and consumption of lettuce away from home was demonstrated (OR = 7.28; 95% CI=2.25-23.57; P=0.0006) in an unmatched case-control study. Environmental investigations revealed that a number of food outlets implicated in the outbreak had common suppliers of salad vegetables. No implicated foods were available for microbiological testing. An environmental audit of three farms that might have supplied salad vegetables to the implicated outlets did not reveal any unsafe agricultural practices. The complexity of the food supply chain and the lack of identifying markers on salad stuffs made tracking salad vegetables back to their origin extremely difficult in most instances. This has implications for public health since food hazard warnings and product withdrawal are contingent on accurate identification of the suspect product.     

Correlation of change in phage type with pulsed field profile and 16S rrn profile in Salmonella enteritidis phage types 4, 7 and 9a.

Using pulsed-field gel electrophoresis (PFGE) and 16S rRNA (rrn) analysis (ribotyping), the in vivo derivation of strains of Salmonella enteritidis PTs 9a and 7 from a strain of S. enteritidis PT 4 has been demonstrated. All strains were isolated from a single patient over a 6-week period. Further studies have demonstrated that in terms of pulsed-field profile and ribotype, the genotypes of the patient-derived strains differed from those of the reference strains of the respective phage types. It is concluded that when used in combination, these methods can provide evidence of phylogenetic relationships in apparently unrelated S. enteritidis phage types isolated during pathogenesis of disease.     

An outbreak of Salmonella enteritidis phage type 34a infection in primary school children: the use of visual aids and food preferences to overcome recall bias in a case control study

Outbreaks of infectious intestinal disease are common in schools. Case control studies are useful in the investigation of infectious disease outbreaks but the time interval between illness and investigation can lead to recall bias, particularly in young children. We describe an outbreak of Salmonella enteritidis phage type 34a infection involving 54 clinical cases in two adjacent schools, and a novel approach to overcome recall bias. The likely dates of infection were identified from the epidemic curve. We created a visual display of the menu from those days and asked 9 cases and 18 matched controls to identify their food preferences from this display. Preference for chocolate mouse was significantly associated with illness (P = 0.006). The results of the case control study agreed with the findings of the environmental investigation. We believe our approach could be used in other circumstances, where subjects are young children or recall bias is a concern.     

Variations in biochemical phenotypes and phage types of Salmonella enteritidis in Germany 1980-92.

The Phene Plate system for typing Salmonella serotypes (PhP-S) is a simple automated typing method based on biochemical fingerprinting. It gives a quantitative value of the metabolism of various substrates by measuring the speed and intensity of each reaction. The ''biochemical fingerprint'' of each isolate is used to calculate similarities among the tested strains with a personal computer program. We used this system to examine a collection of 86 strains of Salmonella enteritidis isolated from human sporadic cases in Germany between 1980 and 1992. Twenty-three biochemical phenotypes (BPTs) consisting of 9 common (C) and 14 single (S) BPTs were identified. BPTs C2 and C4 containing 20 and 36 strains respectively accounted for 65% of the isolates. Strains of BPT C2 were found over a wide period of time whereas strains of BPT C4 were isolated during the period between 1988 and 1992. With phage typing, 11 discrete phage types (PTs) and 18 strains designated as non-specific type (NST) were identified. PTs 4 and 8 with 39 and 17 strains respectively were the dominant PTs. Strains of PT 8 were isolated over a wide period of time whereas all (except one) strains of PT 4 were isolated between 1988 and 1992. Combination of biochemical fingerprinting and phage typing divided the strains into 25 phenotypes (BPT:PTs). Whilst phenotype C2:8 was found over a number of different years, phenotype C4:4 was isolated only between 1988 and 1992. These findings indicate the presence of one persistent and one recently emerged phenotype among S. enteritidis strains in Germany.(ABSTRACT TRUNCATED AT 250 WORDS)     

An outbreak of infections with a new Salmonella phage type linked to a symptomatic food handler.

In December 2001, the South Australian Communicable Disease Control Branch investigated an outbreak of gastrointestinal illness linked to a Korean style restaurant in metropolitan Adelaide. Twenty-eight people were identified as having experienced gastrointestinal symptoms subsequent to dining at the restaurant between 9 and 12 December 2001. A case-control study implicated mango pudding dessert (OR 16.67 95% CI 2.03-177.04) and plain chicken (OR 10.67 95% CI 1.04-264.32). Nineteen cases and one food handler submitted faecal specimens that grew Salmonella Typhimurium 64var. Two samples of mango pudding and one sample of pickled Chinese cabbage also grew Salmonella Typhimurium 64var. The infected food handler reported an onset of illness 2 days before cases first reported eating at the restaurant. The food handler's only role was to prepare the mango pudding dessert in an area external to the restaurant's kitchen. Illness was strongly associated with consumption of a contaminated mango pudding dessert, with contamination most likely resulting from the symptomatic and culture positive food handler who prepared the dish. This outbreak demonstrates the importance of excluding symptomatic food handlers, and the need for appropriately informing and educating food handlers regarding safe food handling procedures. Restaurants with staff and management from non-English speaking backgrounds should be specifically targeted for education that is both culturally sensitive and language specific.