Beware of lemon meringue pie

Microbe of the month: Bernard Dixon on the return of salmonella

With summer around the corner, a warning to campers. Life under canvas can provide the perfect conditions for bacteria to proliferate in foodstuffs, according to a new report of a gastroenteritis outbreak caused by Salmonella enteritidis during a camping holiday in north Wales. Thirty-three people were admitted to hospital with diarrhoea, vomiting and abdominal pain.

Describing the incident in Epidemiology and Infection, Ruairi Brugha of the Central Public Health Laboratory in Colindale, with colleagues in Cardiff and Bangor, points out that infected eggs pose a particular danger to campers. The victims in the Wales case - the first reported outbreak caused by a new type of S. enteritidis discovered in 1993 - were on a trip organised by a Boys and Girls Brigade group. The 12 adults and 37 children (aged nine to 17) brought tents, ovens, cooked and uncooked food from their home town 300 miles away. But they had no refrigeration facilities. Three days after they arrived, 46 of the 49 members of the party went down with gastroenteritis. The condition of 33 of them soon deteriorated, and ambulances ferried the victims to hospital. Thirty-one of them had to be intravenously rehydrated.

The bacteriologists who investigated the incident found the campers had discarded the remains of the meal consumed the evening before the first symptoms appeared. Though they could not test the foods, the investigators screened samples of faeces from all the campers for disease-causing bacteria.

A comparison of these results with the food items eaten by individual campers quickly highlighted lemon meringue pie as the most likely - indeed the only - source of infection. Every one of the 42 individuals who had eaten the pie had become ill. And every one of them had S. enteritidis in their faeces, except one who had eaten only three or four spoonfuls. None of the faecal samples contained any other hazardous microbes.

The pie had been made from eggs, pastry, sugar and lemon powder. The eggs came from a batch laid 13 days before theoutbreak, transported from the campers' home town and stored at the camp in warm summer temperatures for two days before the pie was made. Two cooks produced the pie mixture, containing 20 egg yolks, boiled it for one or two minutes and then left it at ambient temperature for four hours. They added a meringue topping, made with egg white that had also been standing for four hours, and put portions of pie into three ovens at gas mark 6 for five to 10 minutes to brown. The pie then stood at ambient temperature for another 2-3 hours before being eaten.

Tests on the remaining six eggs failed to show S. enteritidis, so the investigators could not pinpoint the source of the outbreak with 100 per cent certainty. However, the dangers posed by this bacterium in eggs and egg products have become clear over the past decade (though Edwina Currie exaggerated the risk in 1988). Together with other evidence, this makes the origin of the Welsh incident virtually certain.

Given that the bacterium can occur in eggs, the ways of preventing it from causing illness are to reduce its chances of growing (by refrigeration) and to kill it (by thorough cooking). On this occasion, S. enteritidis had ample opportunity to multiply while the eggs, pie mixture and pie were left at ambient temperature and the gas ovens were probably too small for the amount of food being cooked, so they did not reach a temperature high enough to kill the bacteria.

Three years ago, the Government's Advisory Committee on the Microbiological Safety of Food produced a report on the dangers posed by bacteria such as S. enteritidis in eggs. It included clear guidelines on the handling and storage of eggs. However, these need to be supplemented by advice specifically directed at campers. Meanwhile, people holidaying outdoors should use cold boxes to carry eggs, and should not prepare lightly cooked egg products under field conditions. Safer still, give up eggs completely for a few days.

Start your day with The Independent, sign up for daily news emails
New Articles
tvDownton Abbey Christmas special
Arts and Entertainment
Wolf (Nathan McMullen), Ian (Dan Starky), The Doctor (Peter Capaldi), Clara (Jenna Coleman), Santa Claus (Nick Frost) in the Doctor Who Christmas Special (BBC/Photographer: David Venni)
tvOur review of the Doctor Who Christmas Special
News
peopleIt seems you can't silence Katie Hopkins, even on Christmas Day...
News
news
PROMOTED VIDEO
News
i100
Arts and Entertainment
Left to right: Stanley Tucci, Sophie Grabol and Christopher Eccleston in ‘Fortitude’
tvSo Sky Atlantic arrived in Iceland to film their new and supposedly snow-bound series 'Fortitude'...
Arts and Entertainment
Jenna Coleman as Clara Oswald in the Doctor Who Christmas special
tvForget the rumours that Clara Oswald would be quitting the Tardis
Arts and Entertainment
Japanese artist Megumi Igarashi showing a small mascot shaped like a vagina
art
News
The Queen delivers her Christmas message
newsTwitter reacts to Her Majesty's Christmas Message
Arts and Entertainment
tv
Life and Style
fashion
ebooks
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Ashdown Group: Marketing Manager/Marketing Controller (Financial Services)

£70000 - £75000 per annum + benefits: Ashdown Group: Marketing Manager/Marketi...

Recruitment Genius: Account Manager

£20000 - £35000 per annum: Recruitment Genius: This full service social media ...

Recruitment Genius: Data Analyst - Online Marketing

£24000 - £35000 per annum: Recruitment Genius: We are 'Changemakers in retail'...

Austen Lloyd: Senior Residential Conveyancer

Very Competitive: Austen Lloyd: Senior Conveyancer - South West We are see...

Day In a Page

A Christmas without hope: Fears grow in Gaza that the conflict with Israel will soon reignite

Christmas without hope

Gaza fears grow that conflict with Israel will soon reignite
After 150 years, you can finally visit the grisliest museum in the country

The 'Black Museum'

After 150 years, you can finally visit Britain's grisliest museum
No ho-ho-hos with Nick Frost's badass Santa

No ho-ho-hos with Nick Frost's badass Santa

Doctor Who Christmas Special TV review
Chilly Christmas: Swimmers take festive dip for charity

Chilly Christmas

Swimmers dive into freezing British waters for charity
Veterans' hostel 'overwhelmed by kindness' for festive dinner

Homeless Veterans appeal

In 2010, Sgt Gary Jamieson stepped on an IED in Afghanistan and lost his legs and an arm. He reveals what, and who, helped him to make a remarkable recovery
Isis in Iraq: Yazidi girls killing themselves to escape rape and imprisonment by militants

'Jilan killed herself in the bathroom. She cut her wrists and hanged herself'

Yazidi girls killing themselves to escape rape and imprisonment
Ed Balls interview: 'If I think about the deficit when I'm playing the piano, it all goes wrong'

Ed Balls interview

'If I think about the deficit when I'm playing the piano, it all goes wrong'
He's behind you, dude!

US stars in UK panto

From David Hasselhoff to Jerry Hall
Grace Dent's Christmas Quiz: What are you – a festive curmudgeon or top of the tree?

Grace Dent's Christmas Quiz

What are you – a festive curmudgeon or top of the tree?
Nasa planning to build cloud cities in airships above Venus

Nasa planning to build cloud cities in airships above Venus

Planet’s surface is inhospitable to humans but 30 miles above it is almost perfect
Surrounded by high-rise flats is a little house filled with Lebanon’s history - clocks, rifles, frogmen’s uniforms and colonial helmets

Clocks, rifles, swords, frogmen’s uniforms

Surrounded by high-rise flats is a little house filled with Lebanon’s history
Return to Gaza: Four months on, the wounds left by Israel's bombardment have not yet healed

Four months after the bombardment, Gaza’s wounds are yet to heal

Kim Sengupta is reunited with a man whose plight mirrors the suffering of the Palestinian people
Gastric surgery: Is it really the answer to the UK's obesity epidemic?

Is gastric surgery really the answer to the UK's obesity epidemic?

Critics argue that it’s crazy to operate on healthy people just to stop them eating
Homeless Veterans appeal: Christmas charity auction Part 2 - now LIVE

Homeless Veterans appeal: Christmas charity auction

Bid on original art, or trips of a lifetime to Africa or the 'Corrie' set, and help Homeless Veterans
Pantomime rings the changes to welcome autistic theatre-goers

Autism-friendly theatre

Pantomime leads the pack in quest to welcome all