The probiotic that could make pregnancy safer

Researchers in UCC have discovered a way to kill listeria, bacteria that are especially dangerous in pregnancy , writes Yvonne…

Researchers in UCC have discovered a way to kill listeria, bacteria that are especially dangerous in pregnancy , writes Yvonne Cunningham

Daily doses of a new "good" bacteria developed in University College, Cork, could protect pregnant women from the dangerous listeria bug.

Researchers have isolated a probiotic - a bacteria which has a beneficial effect when consumed live - that can kill the listeria bacteria. The research was carried out by Dr Sinead Corr as part of her PhD in UCC.

She identified the precise mechanism by which a probiotic protects against disease.


"Usually these organisms are originally isolated from the human gut, they've been shown in the lab to have some kind of beneficial property and then they're put back into dairy products or fruit juices and ingested live by the consumer," says Prof Colin Hill, associate professor in microbiology at UCC.

The probiotic developed in Cork protects against listeria, an organism which causes listeriosis, a particularly dangerous disease for pregnant women and the reason they are advised not to eat paté or soft cheeses.

"Listeria can cause spontaneous abortions in some pregnancies. It's a very rare disease but it has a high fatality rate: 30 to 40 per cent of people who get listeriosis will die as a result," says Prof Hill.

Listeria is also a major concern for the food industry. "There is zero tolerance for listeria in ready-to-eat foods. They have to recall any foods in which listeria shows up - that is a major health cost, and a major financial cost as well."

Dr Corr proved that the probiotic's ability to produce a bacteriocin was the protective agent against listeria.

A bacteriocin is a substance produced by one bacteria to kill another bacteria. "The bacteriocin itself is quite specific, it doesn't go killing everything in the gut, it kills only listeria, so it is unlike an antibiotic which would disrupt your gut flora and give you problems," says Prof Hill.

To find a compound that would kill listeria, researchers had to screen many strains of bacteria. "We isolate bacteria from the guts of healthy volunteers and subject them to tests to find one that is active against listeria. Only a very small number would have that ability," says Hill.

"Only a few of those would grow in milk, and only a few would withstand the kind of technological processes used, so you have to just screen and screen and eventually you end up with one or two strains that you think might have potential," he adds.

Even after all this screening, the Cork scientists weren't sure the bacteria they'd isolated (called Lactobacillus salivarius UCC118) would work. Because listeria is so dangerous, they used an animal model to test it.

They fed one group of mice with a probiotic, another group with a probiotic which couldn't produce the bacteriocin, and a control group didn't get the probiotic at all.

"We found a very very strong protective effect. The level of protection was about 99.9 per cent protection against the organism," says Prof Hill.

"We actually got the result we had hoped for and predicted but hadn't necessarily expected. Science being science, very often you don't," he adds.

Most people can eat listeria and suffer no ill effects from it, even if pregnant.

"But some people, unfortunately, do not have that protective effect and UCC118 is an artificial way of generating that normal protective flora," says Hill.

"Everyone's got a different gut flora, it's as unique a part of you as your fingerprint. Your gut flora establishes itself in childhood and stays with you more or less for your whole life," says Hill

The protective effect of UCC118 is not permanent. "If I gave you a probiotic, it would be there for a day or two after you consumed it, but then it would completely disappear, It can't just establish itself in your stable flora because it's too stable and difficult to colonise," says Hill. The safety of UCC118 has already been proven. "It has been approved completely safe in a human trial," says Hill.

This project has been funded by Science Foundation Ireland through its Centres for Science Engineering and Technology.