Scientists have now discovered how probiotics successfully work in fighting against a number of animal diseases, paving way for their use in preventing and even treating human diseases.
Scientists from University College Cork, Ireland, used three animal models of disease that have human counterparts - bovine mastitis, porcine salmonellosis (a gastrointestinal disease) and listeriosis in mice (an often fatal form of food poisoning) - to demonstrate the protective effects of probiotics.
"Rather than use commercially available probiotics, we made our own probiotic preparations containing safe bacteria such as Lactobacillus species newly isolated from human volunteers," said Dr. Colin Hill, the lead researcher of the study.
He added: "In all three animal diseases we observed a positive effect in that the animals were significantly protected against infection".
Also, the researchers used probiotics to control disease in animals that were already infected.
And the researchers saw that administering these safe bacteria to an infected animal was equally effective as the best available antibiotic therapies in eliminating the infectious agent and resolving the symptoms.
Also, it was found that the protection, in each instance, was linked to a particular bacterial species, and the mechanism of action varied from direct antagonism (where the probiotic directly kills the pathogenic bacteria) to effects mediated by the host immune system.
"It is likely that using probiotics rather than antibiotics will appeal to at-risk individuals since they are safe, non-invasive, do not create resistant bacteria and can even be administered in the form of tasty foods or beverages," Hill said.
"We have shown that we can protect and even treat animals against pathogenic bacteria by introducing harmless bacteria at the site of the infection.
"In order to use similar strategies in preventing or treating human disease we must understand the molecular basis of their efficacy. This understanding will provide the basis for intelligent screening and selection of the most appropriate protective bacterial cultures to go forward into human trials," Hill added.
The study was presented at the Society for General Microbiology meeting in Harrogate.