Article in the Wall Street Journal, written by Laura Johannes.
A strain of healthy bacteria can kill harmful bacteria in lab tests
The Claim: Some probiotics, healthy bacteria commonly known for improving digestion and boosting the immune system, also can kill pathogens, such as those that cause food poisoning and others that cause illnesses such as strep throat.
The Verdict: A probiotic lozenge can reduce incidence of strep throat, according to published research by Italian scientists. A Harvard University scientist found another strain, which is added to some smoothies and raw juices, can kill a wide variety of harmful bacteria in lab tests. The use of probiotics to kill pathogens is a promising area but most of the work is still preliminary, scientists say.
The ability of some bacteria to kill other bacteria isn’t new—foods such as yogurt, sauerkraut and pickled cucumbers are preserved thanks to a type of bacteria that produces lactic acid, which is lethal to harmful bacteria, says Maria L. Marco, associate professor in the Department of Food Science & Technology at the University of California, Davis.
Scientists increasingly are studying molecules called bacteriocins released by some bacteria. Bacteriocins, at least in theory, can work like natural antibiotics when produced by probiotic bacteria—potentially protecting people from illness and disease without the need to take a drug.
Most of the work so far is in the lab only. For example, in as-yet-unpublished work, Harvard Medical School microbiologist Andrew B. Onderdonk found that a bacterial strain, Lactobacillus bulgaricus GLB44, can kill a variety of harmful bacteria, including food pathogens salmonella and Escherichia coli. Its apparent ability to eliminate a broad range of harmful bacteria is “striking,” says Dr. Onderdonk. Lab tests suggest the probiotic releases bacteriocin to kill the bacteria, though the bacteriocin hasn’t yet been identified, says Rositsa Tropcheva, assistant professor of biotechnology at Sofia University in Bulgaria.
The GLB44 strain is sold by ProViotic AD, of Sofia, Bulgaria. Neither of the scientists have a direct financial link to ProViotic, though the company has funded some of their research.
L. bulgaricus GLB44 is closely related to bacteria found in many yogurts. It is isolated from a flower and cultured in carrot juice, so is vegan, says ProViotic Chief Executive Kiril Petkov. As a supplement, it costs $40 for 30 capsules. It is also available as a $2 smoothie “booster” at Juice Press bars in New York and Connecticut, says Juice Press LLC Chief Executive Marcus Antebi. Juice Press also adds it to several of the raw juices sold at its stores. Juice Press and ProViotic are separate companies but work together closely; a majority of Juice Press shareholders have a stake in ProViotic.
Scientists say GLB44 isn’t even close to being proven effective at preventing people from getting sick from foodborne bacteria in raw or undercooked food. Just because it kills pathogens in the lab doesn’t mean it will work in humans or even in laboratory mice, says Colin Hill, a microbiologist at University College Cork in Ireland. His research team found 10 bacterial strains that were highly effective in laboratory tests at combating the foodborne pathogen Listeria monocytogenes, but only one of those strains protected mice from death when injected with the pathogen, he says. In a 2007 paper in the Proceedings of the National Academy of Sciences, Dr. Hill and colleagues proved that the strain's efficacy in killing listeria was thanks to a bacteriocin.
The bacterial strain that saved the mice from listeria poisoning isn’t available commercially. The university is seeking to license for sale other probiotics that kill harmful bacteria, including a strain that targets Clostridium difficile, which can cause diarrhea after a person is treated with antibiotics.
Several probiotics, have been shown in humans to combat Helicobacter pylori, which causes ulcers, according to published work But more research is needed to determine if probiotics are an effective treatment for ulcers, scientists say.
Another probiotic releases two bacteriocins that act against bacteria that cause strep throat, according to a 2012 study published in the International Journal of General Medicine. In the study of 82 children, most of whom had recurrent strep throat, those who consumed the probiotic for three months had a 90% reduction in episodes of illness compared with the previous year. Children in a control group not taking the probiotic experienced an increase in illness.
The study tested an Italian version of the probiotic, but the same bacteria is available in a lower dose in the U.S. under the product name BLIS K12, says John Hale, research and development manager of Blis Technologies Ltd., in Dunedin, New Zealand. Since the probiotic acts in the mouth, most of the products are sold in the form of lozenges, he adds. The study, and an adult study which also showed a reduction in strep throat with probiotic use, were co-authored by Francesco Di Pierro, scientific and research director at Italy’s Velleja Research, which developed a version of the probiotic sold in Italy and which receives royalties on it.