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Listen to this siteThursday 13 September 2007
Food Survey Information Sheet 05/07
Between November 2005 and January 2007, eggs purchased from 1,567 catering premises in the UK were tested for salmonella contamination. Eggs from eight different countries were tested. Most of the eggs originated from the UK (89.0%).
Salmonella was found on the shells of six samples, of which one was also contents positive, giving a prevalence of 0.38%. Five of the positive samples were from the UK and one was produced in Germany. Salmonella Enteritidis was the most common serotype (0.31%) with phage type (PT) 4 being the most common phage type (0.19%).
The survey showed evidence of poor egg storage and handling practices in catering premises. Half (55%) did not store their eggs under refrigerated conditions, a fifth (20.7%) of egg samples had expired best before dates or were in use after three weeks of lay indicating poor stock rotation, and 37.1% mixed and pooled eggs for use during the day.
Back to topThe aims of the survey were to:
Salmonella infection remains an important public health problem in the UK. During the period from 1981 to 1991 the number of cases of salmonellosis in the UK in humans rose by approximately 170%. Subsequent investigations have shown that eggs caused a significant number of these outbreaks. Surveys and investigations of eggs for salmonella contamination have played an important role in understanding the extent and pattern of contamination.
Outbreaks caused by salmonella have been linked to a great variety of foods, and have been closely associated with egg and egg products but it is the way in which eggs are used in catering establishments that have given particular cause for concern. Since 2002, the emergence of egg associated Salmonella Enteritidis strains other than the strain PT4 has increased with three quarters of these outbreaks occurring in commercial catering premises.
As a substantial number of outbreaks of Salmonella Enteritidis infection described above have occurred in catering premises in England and Wales, information on the incidence of high-risk egg preparation methods that allow the growth or survival of Salmonella Enteritidis in eggs in these premises was needed.
The Agency set up a series of raw shell egg surveys: this survey of eggs at the catering level, and previously one of non-UK eggs at the retail level. The results from these surveys will contribute to providing an indication of where particular contamination problems are occurring and hence where interventions to reduce salmonella contamination might best be focused.
Seasonal effects or prevalence within countries were not investigated in this survey. Samples were taken at random from catering premises in England, Scotland, Wales and Northern Ireland.
The Health Protection Agency (HPA) coordinated the survey and samples were collected by experienced staff from 238 local authority environmental health departments. Eggs were identified by the stamp marking on the egg shells and samples were collected from the shelves at random. A range of information concerning the eggs was collected including details of the type of caterer and type of cuisine, sampler details, storage temperature of eggs, size of eggs, pooling of shelled eggs, packing station number, country of origin, production types, sell by date, best before date, vaccination scheme and brand name. All the methods used are HPA standard operating procedures.
Any catering premises could be included in the survey provided they obtained their eggs from wholesale suppliers and not retail outlets. Catering premises were selected in a manner designed to minimise bias towards particular premises types. The proportion of premises of each category within the list of those sampled was intended to reflect the proportion within the local authority's area. Within each premises category in the local authority’s database of food businesses, individual premises were selected without bias by either using a random number generator or selecting every tenth entry.
In terms of egg sampling, the number to be tested to achieve this objective depended on the estimated previous level of contamination and allowing for any change that may have taken place. It was estimated that a sample size of approximately 1,600 eggs in groups of six in the course of a year would be needed to measure an estimated prevalence of around 1%.
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(pdf 1MB) Results of survey of salmonella in catering eggs Read the survey resultsDownload excel
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