Outbreaks of food poisoning could be caused by an industry standard cleaning procedure used for fresh produce like salads, according to scientists in the UK.
The researchers, at the University of Southampton, said the practice of washing fresh produce with chlorinated water is supposed to kill or reduce the number of bacteria on food but it is actually making them undetectable.
Standard Practice
"It is good standard practice to chlorinate, disinfect foods to reduce those numbers but our work is showing in fact that this is masking the problem and you may not be killing the pathogens at all," Professor Bill Keevil, Head of the Microbiology Group at the University of Southampton, told Reuters.
The team have shown that many bacteria survive the stress of coming into contact with chlorine by shutting down, or becoming viable but nonculturable, a state that also renders them invisible to standard laboratory safety tests.
"This is absolute proof they are still alive, they are still capable of causing infection. So the implications for this are broad. So for a start we have these many outbreaks of disease that cant be traced. Are the due to stressed, viable but not culturable bacteria that are missed using routine approaches?," Keevil said.
The team have shown alternative, molecular bacterial detection techniques used by some laboratories to test food safety are also unreliable.
Foodborne Illness
Outbreaks of food poisoning are blamed for more than 400,000 deaths, according to the World Health Organisation. In the UK, the government estimated a million people a year suffer a foodborne illness, resulting in 500 deaths.
"We think the foodchain does need to sit up and take notice because they've been relying on this common disinfection procedure for oh, a hundred years, particularly for drinking water supplies. It's stood us in good stead," Keevil said.
"It's certainly reduced outbreaks of disease particularly from drinking water but with the many unidentified outbreaks it's making us think again. Is this because pathogens are stressed and they're being missed?"
Keevil said we need to take additional precautions when preparing food, thoroughly washing any raw food including salads, lettuce, cucumber and tomatoes, particularly where chlorine washing has been used.
The study was published in mBio, the lead journal for the American Society for Microbiology.
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