LONDON, April 18 (Xinhua) -- Foodborne pathogens can be made undetectable by chlorine, which is widely used in the agriculture industry to decontaminate fresh produce, according to a study released Wednesday by the University of Southampton.
Foodborne disease is responsible for an estimated 2.2 million deaths worldwide annually, and in the UK, it is estimated that each year one million people suffer a foodborne illness, resulting in 500 deaths, said the University.
In this study, the team, led by the University, incubated Listeria monocytogenes and Salmonella enterica populations on spinach leaves and then subjected the spinach to chlorine washes.
In response to stress such as extreme temperatures, nutrient starvation, or significant dryness, some Gram-positive bacteria can form tough spores and survive for thousands of years in the environment.
Many bacteria, however, cannot form spores and instead survive a stress by entering a viable but nonculturable (VBNC) state in response to environmental stresses.
The team found that the viable Listeria and Salmonella populations became VBNC by 50 and 100 parts per million (PPM) chlorine, respectively. Further experiments revealed that roundworms that ingested VBNC cells had shortened life spans.
Chlorine induces the VBNC state in foodborne pathogens Listeria monocytogenes and Salmonella enterica and chlorine was ineffective at killing total populations of these pathogens, said lead author Professor Bill Keevil, Head of the Microbiology Group at the University of Southampton.
"VBNC cells cannot be detected by standard laboratory culture techniques, presenting a problem for the food and water supply industries, which uses these techniques to detect potential disease contaminants," he added.
The study has been published in the journal mBio.