August 15, 2014

expert reaction to PHE investigation of Salmonella outbreak

Public Health England (PHE) announced an investigation into a outbreak in over 150 people of a type of Salmonella Enteritidis.

Dr Kimon-Andreas Karatzas, a food microbiologist at the University of Reading, said:

“Salmonella is quite common and found in the intestines of chickens, which is why outbreaks are often associated with chicken or egg products in the human food chain. Salmonella is totally harmless to chickens, but pathogenic to humans – in other words, it makes us ill. While it is not as deadly as Listeria monocytogenes (most deadly foodborne pathogen with 30% mortality rate) it is the second most common cause of foodborne disease in the UK after Campylobacter. However, it has very low mortality rates and the disease is usually associated with vomiting and diarrhoea which can last between 1 to 7 days. Since it can cause dehydration it can be particularly bad for the elderly or those with underlying health problems.

“Salmonella is found naturally in the intestines of reptiles and birds and there have been cases where people developed salmonellosis just by handling such animals even as pets. However, this specific outbreak seems to have been caused by a strain of Salmonella Enteritidis which is often associated with poultry or eggs.

“As it is found in chicken faeces, most eggs are contaminated on their surface when just laid. However, high standards of food production and preparation can minimise the risks of transferring salmonella into the human food chain. Meat producers with high welfare and production standards reduce the risks of producing chicken which is contaminated, but chicken should still be properly cooked through before eating to kill off any bugs that remain.

“From the details given so far about this outbreak, it sounds as if it will be linked to a contaminated prepared Ready-to-Eat food product. The strain that denotes poultry origin suggests that the food product might contain something prepared from chicken or egg origin from which salmonella was not eliminated. However, this serotype has caused outbreaks in the past that were not linked to food products with chicken ingredients. In these cases either equipment that was contaminated with Salmonella was used without thorough cleaning or water containing salmonella contaminated the product.

“Until the source is found, there is little that people can do to protect themselves, other than remembering to take care when handling raw meat and eggs and making sure food is cooked properly before eating.”

Professor Anthony Hilton, Head of Biological & Biomedical Science at Aston University, said:

“If the cases are related the next important stage will be identifying common risk factors which are associated with the infected individuals.  This might be consumption of a contaminated food or ingredient or even a common exposure at an event or activity.

“Compiling food and exposure histories of cases occurring over several months can be complex and time consuming depending on the quality of the information available and it may be some time before we know the true extend of the outbreak and the causative link, if any.”

Declared interests

None declared