Clinicians Briefing - Sandwiches possibly contaminated with listeria
Updated 23 March 2007
This document provides some background information to clinicians caring for patients thought to have eaten preprepared sandwiches possibly contaminated with Listeria.
Background
Listeria monocytogenes (>100cfu/ml) has been identified in preprepared sandwiches produced by Anchor Catering and tested between 19 February 2007 and 12 March 2007. These sandwiches are made by a company that supplies some hospitals in London and the South East. Typically around 500-1700 sandwiches may be supplied to a hospital in a week.
A number of uncertainties exist. It is difficult to quantify the risk of infection following the ingestion of a contaminated sandwich and it is difficult to estimate the proportion of product contaminated with L .monocytogenes. However, it is known that some of the product and the environment were contaminated with L. monocytogenes at high levels when tested in February and March. The risk will depend on the level of contamination at the point of manufacture, the storage conditions of the sandwich and the amount of contaminated food consumed. Although the risk of infection is dose dependent, it is difficult to make an assessment of the quantity of organisms that is required to cause an infection. Host factors will also play a part particularly the level of immune compromise. Other factors contributing to vulnerability are increasing age, pregnancy and underlying conditions such as liver disease, renal disease, malignancy, immunosuppression etc.
Over the last few years a large proportion of infections have presented as bacteraemic infections, particularly in the over 60 years age group.
Clinicians should seek advice from their local microbiologist if they suspect a patient has listeriosis (see Annex 1 below), both for the laboratory diagnosis of listeriosis and for advice on treatment.
Although L. monocytogenes infections are not notifiable, clinicians are urged to report such infections to the Consultant in Communicable Disease Control (CCDC) in their local Health Protection Unit. Microbiologists should ensure that isolates are sent to the HPA Centre for Infections (CfI) for further characterisation.
Many foods have been implicated as vehicles of infection, mainly via cross contamination, with sandwiches implicated in three previous incidents. A list of these is in Table 1.
Annex 1
L. monocytogenes can cause a variety of diseases. Infections range from a mild flu-like illness to severe disease. Infections in pregnancy may precipitate premature birth or miscarriage. Infections in the neonatal period may present with meningitis. Patients whose immunity to infection is impaired, such as those with haematological or solid organ malignancies and transplant recipients may develop septicaemia or meningitis. The infection can be treated with antibiotics; however, in about one third of cases the disease is fatal. Case fatality ratio varies according to co-morbidity.
L. monocytogenes has been found in the faeces of up to five per cent or more of normal healthy people.
Incubation period: Incubation period can be few days up to 90 days.
Clinical symptoms include, fever, myalgia, malaise and backache. Occasionally the disease manifests as a food poisoning with diarrhoea, abdominal pain, nausea and/or vomiting. Severe forms include septicaemia, meningitis and encephalitis.
Diagnosis: Invasive listeriosis is diagnosed when the organism is cultured from a site that is usually sterile, eg blood or CSF. The organism grows readily within 36hrs.
Treatment of listeriosis in adults: Amoxicillin IV 2gm 4-hourly for 10-14 days plus or minus gentamicin 7mg/kg daily, please contact the microbiologist for advice and monitoring of once daily gentamicin.
Specialist advice should be sought from a microbiologist when treating infections during pregnancy or for neonates before commencing therapy.
For penicillin allergic patients specialist advice should be sought before commencing treatment. Treatment will depend on the nature of the allergy (level of cross-immunogenicity in patients with a history of penicillin-related anaphylaxis). Meropenem, Cotrimoxazole and chloramphenicol have been used in the past.
Further reading:
HPA website
Listeria webpages
Changing pattern of human Listeriosis, England and Wales, 2001-2004
http://www.cdc.gov/ncidod/eid/vol12no09/05-1657.htm
eating while you are pregnant - FSA publication
http://www.food.gov.uk/multimedia/pdfs/life02eatingwhenpregnant.pdf#page=11
Association of Microbiologists - leaflet on listeria
http://www.amm.co.uk/files/factsabout/fa_list.htm
Update on human listeriosis in the United Kingdom
http://www.food.gov.uk/multimedia/pdfs/acm814att.pdf#page=3
The changing epidemiology of listeriosis in England and Wales - graphs from Communicable Disease Report http://www.hpa.org.uk/cdr/archives/archive05/News/news3805.htm#list
Listeriosis prevention Clinical infectious diseases 44 521-528 &529-530
Additional information:
Table 1. Possible and probable associations with food types and cases of listeriosis in England and Wales
| Year | Area | Number of cases | Food vehicle for infection |
|---|---|---|---|
| 1986 | London | 1 | mould ripened soft cheese |
| 1988 | London | 1 | Greek style soft cheese |
| 1988 | NE England | 1 | cooked chicken |
| 1988 | NE England | 1 | vegetable rennet |
| 1987-9 | Nationwide | 355 | Pâté |
| 1999 | NE England | 4 | Hospital sandwiches |
| 2003 | NE England | 17 | Butter |
| 2003 | S Wales | 2 | Hospital sandwiches |
| 2003 | SW England | 5 | Hospital sandwiches |
| 2004 | SE England | 2 | Hospital sandwiches |
| 2005 | NW England | 1 | Sliced meat |
| 2006 | London | 1 | Sliced meat |
Last reviewed: 5 February 2008