Another two people have died in England as part of a Listeria outbreak linked to eating pre-made sandwiches, bringing the total deaths to five.

Whole Genome Sequencing analysis by Public Health England (PHE) has identified three more infections bringing the total number to nine. All cases had existing medical conditions or are from vulnerable groups in healthcare settings.

PHE analyzed previously known cases of Listeria from the past two months to see if they were linked to the outbreak. PHE figures show seven Listeria cases in the week ending June 9, six the previous week, and four in the week before that. The previous three weeks all reported two infections.

Dr. Nick Phin, from PHE, said there have been no patients linked to the incident from outside healthcare organizations as yet.

“Swift action was taken to protect patients and any risk to the public is low. PHE is continuing to analyse all recent and ongoing samples of listeria from hospital patients to understand whether their illness is linked to this outbreak.”

All cases were in hospital patients in England. Affected sandwiches and salads were withdrawn from hospitals when the link to Listeria infections were identified. Chicken is the suspected contaminated ingredient.

Individuals are thought to have eaten affected products before the withdrawal took place from 43 NHS trusts on May 25. Listeria monocytogenes at levels of 190 colony forming units per gram was detected in the pre-packed sandwiches. The infective dose was estimated to be 10 to 100 million CFU in healthy people, and only 0.1 to 10 million CFU in individuals at high risk of infection, according to a study in the International Journal of Food Microbiology in 1996.

Suspected cross contamination

The supplier, The Good Food Chain, voluntarily ceased production while investigations continue. The firm had been supplied with meat produced by North Country Cooked Meats which produced a positive result for the outbreak strain of Listeria. This business and North Country Quality Foods who they distribute through, have also voluntarily ceased production.

The Good Food Chain confirmed its production facility in Stone, Staffordshire was cross contaminated by an ingredient from an approved meat supplier.

“The business has operated in the food industry for almost a quarter of a century and has an excellent reputation for food safety and quality,” according to a company statement.

Its Stone facility is regularly audited and recently renewed its BRC Grade A accreditation and a five-star rating from the local Environmental Health Officer as well as holding STS accreditation. On an ongoing basis, The Good Food Chain regularly laboratory tests its supplies, finished products and environment in line with industry guidelines and best practice.”

‘An unnecessary tragedy’

Craig Smith, chairman of the Hospital Caterers Association, said it was “deeply saddened” by the Listeria outbreak and called it an “unnecessary tragedy.”

“We understand other suppliers who have purchased products from North Country Cooked Meats have also been affected and recalls are underway. We urgently request hospital caterers to identify all products in their menus which contain ingredients from North Country Cooked Meats and North Country Quality Foods so they can be isolated, removed and further investigations can be undertaken,” he said.

“We would like to reinforce the critical importance of temperature control and call for all caterers to review their audit processes with immediate effect. We demand the highest standards from our supplier members and expect them, without exception, to temporarily suspend delivery of products until they have been fully re-evaluated and identified as ‘not at risk’ from the positive test for Listeria at North Country Cooked Meats.

“Our patients are some of the most vulnerable people in society and we must all go the extra mile to protect them. Failure in food safety systems are unacceptable and immediate action must be taken.”

The University Caterers Organization (TUCO) confirmed The Good Food Chain was a supplier on the TUCO Framework Agreement for Sandwiches and Associated products.

The firm and its products have been suspended until further checks are completed with food safety auditors STS.

“Very few of our members used this particular supplier and we are in touch personally with each of those affected to arrange a suitable alternative. Since learning of the localized outbreak, the procurement team have been in touch with suppliers across all relevant TUCO frameworks to ensure that any products linked to either supplier are removed from the supply chain immediately.”

Speaking before the case update, professor Jose Vazquez-Boland, chair of Infectious Diseases, Infection Medicine – Microbial Pathogenesis at the University of Edinburgh, said pre-packed sandwiches have been incriminated in past listeriosis outbreaks.

“In 2017 for example one such episode in Yorkshire and The Humber involved also sandwiches supplied to hospitals. There is clearly a warning here that microbiological controls for Listeria need to be stepped up with pre-packed sandwiches,” he said.

“Clearly Listeria foodborne outbreaks are caused by deficiencies in food safety measures and the microbiological control of food products along the production and distribution chain. However, these checks may fail or be insufficient and Listeria may pass undetected. This is what has probably happened in this case.”

(To sign up for a free subscription to Food Safety News, click here.)