REPORT OF THE GREATER MANCHESTER/LANCASHIRE/PRESTON
MICROBIOLOGY SERVICES LIAISON GROUP SURVEY OF THE
MICROBIOLOGICAL EXAMINATION OF RAW SHELL CHICKEN EGGS
FROM RETAIL OUTLETS
K Williamson, G Allen, F J Bolton
Food and Environmental Microbiology Services, Preston
Date of report 26/02/04
Survey Code No: 304011
Introduction
Despite the significant effort directed at reducing the Salmonella contamination of
eggs which was one of the main microbiological food safety issues of the 1990’s,
there is a need for further research in this area.
The number of reported cases of S. Enteritidis PT 14b has risen sharply from less than
200 a year prior to 2001, to 698 in 2002 and 922 in 2003.
The descriptive epidemiological evidence from CDSC relating to the recent increase
in the human isolates of S. Enteritidis PT 1b and S. typhimurium PT U277 suggest
that contaminated shell eggs might be the source.
Although epidemiological findings indicate that the people who had been ill were
more likely to have consumed eggs outside the home, it was thought relevant to carry
out a survey from retail premises to help substantiate this hypothesis.
Campylobacter is the most common cause of bacterial gastroenteritis in the UK
accounting for around 50,000 cases of illness a year, but the etiology of this infection
remains only partly explained. Hence as well as the rationale for conducting a survey
on Salmonella in eggs being strong, the opportunity to examine the outside and
contents of the eggs for Campylobacter is also valid.
Materials and Methods
Sample Collection
This survey was carried out as part of the Greater Manchester FLG/Lancashire
FOG/FEMS-NW Preston sampling programme during September - December 2003.
Samples comprised of six hen eggs of any type i.e. free range/barn eggs/organic/lion
quality/UK produced/imported etc. The samples were purchased from as wide a
range of retail premises as possible including supermarkets, farm shops, market stalls
and mobile vendors. Eggs were retained in their protective container or transferred to
clean new containers, packed in a food grade plastic bag and transported to the
laboratory at ambient temperature.
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A standard FEMS–NW food request form was completed with additional details
being recorded in the sampling officers PACE notebook.
Sample Examination
A total of 343 samples of six eggs were submitted from 25/26 authorities in Greater
Manchester and Lancashire as detailed in Appendix 1.
The pooled shell swabs and contents from each 6 egg sample was examined for
Salmonella and Campylobacter using UKAS accredited FEMS North West food
methods.
Results
Table 1
Microbiology results n = 343 (pooled egg shells)
Salmonella spp
Campylobacter spp
Table 2
Detected
0
0
Not detected
343
343
Microbiology results n = 343 (pooled egg contents)
Salmonella spp
Campylobacter spp
Detected
0
0
Not detected
343
343
Discussion
The primary objective of this survey was to determine the prevalence of Salmonella
contamination of raw shell hen eggs from retail premises at the point of sale.
Salmonella was not detected from any of the samples examined in this study. This
data helps to support the epidemiological findings that people who have been ill with
Salmonella associated with egg were more likely to have consumed the eggs outside
the home and prepared by caterers. The egg supply chain to the catering market
differs to that of the retail market; caterers receive most of the small volume of
imported eggs and eggs not produced under UK assurance schemes (1). Previous
studies of eggs have shown imported eggs to have a higher rate of Salmonella
compared to UK produced eggs. The nature of the catering egg market may allow the
sporadic introduction of highly contaminated eggs which may account for the
intermittent cause of outbreaks associated with Spanish eggs.
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The handling and storage of eggs within catering premises is also often different than
in the domestic kitchen. Half the caterers visited in a recent study (1) did not store
their eggs under refrigeration, a now common practice in the domestic kitchen. More
research is required to investigate the prevalence and types of Salmonella related to
country of origin.
While the widespread contamination of poultry with Campylobacter is well
documented the possible spread of Campylobacter by handling or consuming eggs is
less clear. It has been highlighted that in order to work towards a 20% reduction in
foodborne disease by April 2006 in line with the Food Standards Agency’s target,
more emphasis needs to be placed on Campylobacter.
Campylobacter was not isolated from any of the 343 pooled shell surface swabs or the
pooled egg contents in this study.
This information helps to support previous studies which indicate low viability in the
egg due to high pH and presence of bactericidal compounds. The high susceptibility
of Campylobacter to dessication and atmospheric oxygen are thought to be a primary
reason for its low survivability on the egg surface. However previous local studies
such as detection of Campylobacter on the packaging of chicken have shown that
Campylobacter does not always behave as expected (Survey No. 904015). Hence the
potential for transmission of Campylobacter from the surface of contaminated eggs
may require more research.
Conclusion

Salmonella and Campylobacter were not detected from the egg surfaces or
contents from any of the 343 pooled samples examined.

The eggs examined in this study were sampled from retail premises. It must be
reinforced that caterers in particular may use eggs produced under less stringent
conditions than those adopted and available at retail outlets in the UK. There is a
need to be aware of the continuing Salmonella hazard presented by eggs,
particularly if serving to the elderly, very young or immuno-compromised
persons.
References
(1)
Microbiological Examination of Raw Shell Eggs and their use in Catering
Premises. LACORS/HPA Co-ordinated FLG Study Report, March 2004.
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Appendix 1
-
Participants
Barrow
Blackburn
Blackpool
Bolton
Burnley
Bury
Chorley
Fylde
Hyndburn
Lancaster
Manchester
Oldham
Pendle
Preston
Ribble Valley
Rochdale
Rossendale
Salford
South Lakes
South Ribble
Stockport
Tameside
Trafford
West Lancs
Wigan
Wyre
TOTAL
KW/KLM (304011rep)
Total number
of samples
11
16
11
4
6
16
20
17
14
16
4
16
13
16
0
16
16
16
16
15
13
13
16
16
11
15
343
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