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Advice for Caterers on Eggs
Background to S. Enteritidis
• There are approximately 2,400 known serotypes of salmonella but the most
important type in human infection worldwide is Salmonella Enteritidis (SE)
• During the late 1980s there was a sharp increase in the occurrence of SE worldwide.
Investigations implicated poultry as a source and poultry meat and shell eggs as
food vehicles
• SE is invasive in poultry and can cause clinical disease resulting in death in young
chicks
• The public health importance of SE is related to the fact that the organism can be
isolated from the contents of intact shell eggs and it has been demonstrated that
reproductive tissue can be infected.
• Production of infected eggs by hens carrying the organism is sporadic - experimental
work by the Public Health Laboratory Service (PHLS) in 1989 showed that only
around 1% of all the eggs from a known infected flock contained salmonella, with
less than 3% of the eggs of individual infected hens found to be contaminated
• The chances of an individual becoming infected from a single egg are very small if
the egg is correctly handled, and the risk has been markedly reduced by the Lion
Code vaccination policy.
• The principal site of contamination in egg contents appears to be either the outside
of the yolk membrane or the albumen surrounding it.
• The yolk membrane becomes more permeable during storage and growth of SE,
associated with invasion of yolk contents, can occur when eggs are stored at 20°C
for more than three weeks.
Why did S. Enteritidis spread in the 1980/90s?
• Feed contamination initially (no evidence but appeared in layers,
broilers and ducks)
• Primary breeders infected in 1980s (spent breeders 1998, chicks
entering Japan, Netherlands, but not Australia)
• Widespread infection in broiler breeders late 1980s/early 1990s
• Infection – less well defined – in layer breeders late 1980s/early
1990s
• Enteritidis is one of the few serotypes that can effectively spread
via the transovarian route
• Human cases of S. Enteritidis in the UK rose sharply in the late
1980s. Although they levelled out in the early 1990s following
legislative measures, they began to rise again in the mid 1990s
Human Salmonella
Trends in human salmonellosis in England and Wales
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UK egg industry response
• New Lion Code of Practice introduced in 1998
• Salmonella vaccination
• Registration and traceability – passport system
• Hygiene, time and temperature controls
• Best-before date and Lion Quality mark on egg shell
• Independent auditing – EN 45011
• The Lion mark on egg boxes and egg shells shows that the eggs have
been produced by British hens conforming to the Lion Code of Practice
• More than 85% of UK eggs are now produced under the British Lion
scheme
UK Results
Trends in human salmonellosis in England and Wales
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UK Results
• Since the launch of the Lion Code of Practice, salmonella has been virtually
eliminated from British Lion eggs
• An EFSA report published in 2007 analysed the results of an EU-wide
survey which sampled and tested the environment on egg layer flock
holdings.
• Several countries reported levels of salmonella of public health significance
on their flock holdings of more than 50%, while the UK figure was only 8%.
• 2008 figures have shown that, in the UK, salmonella of public health
significance on flock holdings has since fallen to 1%.
• An FSA survey of UK eggs on retail sale in 2004 found no salmonella in
28,000 eggs tested
• Several other European countries have experienced continued outbreaks of
salmonella and there were outbreaks among humans in the UK in 2009
directly linked with imported eggs.
• An FSA survey of imported eggs on sale in the UK, published in 2006,
found egg shell and/or contents contamination in one in 30 boxes of six
eggs sampled. HPA tests on imported eggs in 2004 found nearly 7% tested
positive for salmonella. In the same HPA investigation, salmonella was not
recovered from any British Lion eggs.
Identifying eggs
Handling Eggs
• Growth of salmonella can be prevented or minimised by low temperature storage, particularly in
the kitchen, where temperature fluctuations can accelerate changes to yolk membrane
permeability.
– Eggs should therefore be kept at a constant temperature below 20ºC to prevent deterioration
in yolk membrane permeability and minimise growth of any micro-organisms that may be
present.
– Caterers should store eggs in a refrigerator. If this is not possible they should be stored in the
coolest storage area available and orders kept to a minimum volume and regularly delivered.
• Eggs should be stored separately from other foods, preferably in the egg box. Eggs should be
brought to room temperature before cooking,
• At room temperature homogenised egg provides an ideal medium for the growth of micro-
organisms and it is therefore essential to avoid any risk of cross-contamination.
• Cooked egg dishes should be eaten as soon as possible after cooking and, if not for immediate
use, should be stored in the refrigerator.
• Hands should always be washed before and after handling shell eggs. Cracked or dirty eggs
should not be used.
• Department of Health advice issued in 1988 recommended that recipes for uncooked dishes
involving the use of raw eggs should be avoided, and that lightly cooked eggs should not be
served to vulnerable groups - ie infants, pregnant women, elderly and debilitated people.
However, this advice pre-dates the introduction of the British Lion scheme which has virtually
eliminated salmonella from British Lion eggs
• In the catering industry, where pooling of eggs is common, pasteurised egg products should be
substituted for raw eggs.
Advice for Caterers on Eggs
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