Common sanitisation practices for lettuce may not be sufficient

You may want to keep your plate devoid of romaine lettuce as a recent study has suggested that common sanitisation practises may not remove all the bacteria present from the crisp veggie.

The Purdue University study shows that the bacteria Listeria monocytogenes can live inside the tissue of romaine lettuce, suggesting that conventional post-harvest sanitization practices might not be sufficient to kill the potentially lethal pathogen.

Research showed that the bacteria could live within lettuce in every stage of the plant growth process, residing inside the plant tissue. L. monocytogenes can gain entry into the plant through cracked seed coats, small tears in root tissue during germination and damaged plant tissue.

The researchers found that exposing lettuce to the bacteria could lead to infection of plant tissue in as little as 30 minutes.

"Knowing this can happen, we need to keep it on our radar as we continue to follow good agricultural practices," lead author Amanda Deering said.

When ingested, the bacteria can be deadly to those with vulnerable immune systems, including pregnant women, the elderly, infants, or those with HIV. L. monocytogenes can also cross the placental barrier in pregnant women, which can trigger a miscarriage.

"For immune-compromised consumers, it's important to remember, that canned or cooked produce is better," Deering noted.

While commonly associated with ready-to-eat deli meat and hot dogs, outbreaks of listeriosis - the disease associated with the bacteria - have also been caused by contaminated celery, cantaloupe, sprouts and apples. A 2011 outbreak from cantaloupe was the second most deadly foodborne bacterial outbreak in U.S. history. The bacteria can only be killed by heat and the contaminated fruit that was minimally processed and consumed raw.

Symptoms of listeriosis may take as long as two months to appear, and by that time, most people don't connect the illness to something they ate, Deering said.

The study appears in Journal of Food Protection.