Green salads long associated with good health, can cause food poisoning due to due to contamination with poisonous bacteria, according to a new research.
Though uncommon, food poisoning caused by eating plants does occur according to the research quoted by magazine.
Vegetables that are fertilized with animal manure, containing pathogens, pose the biggest threat. Raw salad vegetables are now washed after harvesting to reduce the risk of contamination.
Apparently healthy green salads are sometimes contaminated with poisonous bacteria which even though rising would not remove. Researches found that harmful bugs can enter lettuce plants through its roots and end up in the edible leaves.
It was after an outbreak of poisoning by the potentially fatal strain of Escherichia coll that was connected with pre-washed lettuce, that food microbiologist kari Matthews and his colleagues at Rutgers university in new jersey in the united states started investigating whether bacteria were getting inside the lettuce, rather than just sitting on the leaves.
The team according to Nature grew lettuce in manure inoculated with E. coli. After sterilizing the plants’ surface with bleach, the researches still found bacteria within the internal tissues that are used for water transport.
Lettuce leaves, researchers found, could be infected by simply irrigating plants with bacteria-inoculated water, despite the fact that foliage did not did not come into direct contact with the water.
Water used to irrigate fields could pose an infection risk, warms Matthews. Although the use of compost manure is regulated, “if you’re using surface irrigation there’s still a chance that the edible portion of the plant can be contaminated”, he says.
“No one has checked to see whether (bacteria) are on the surface of the plant or within,” agrees William Waites, a food microbiologist at the University of Nottingham, Britain.
His group’s research, according to nature, reveals a similar uptake to E coli and Listeria bacteria by spinach. Bacteria also accumulate in the plants over time, the group found. Levels increased up to 30 days, around the time the plant would be harvested, says Waites.
Nature quotes Mathews as saying the concentrations of bacteria used in the lab experiments are probably far higher than those that occur on farms. After all, poisoning by salad is not common. The team is now working to establish whether salad vegetable grown on farms are also contaminated by E coli or by other bugs.