Researchers are now investigating the potential of a probiotic bacterium in treating MRSA infections.
These include oxacillin, flucloxacillin, and dicloxacillin.
About 53 percent of S. aureus isolates (which are individually analyzed S. aureus bacteria) in the United States in 2005 alone were antibiotic-resistant.
For this reason, it is important to find different ways of attacking and destroying this bacterium in infected people — before it puts their health into serious jeopardy.
A new study by investigators from the National Institute of Allergy and Infectious Diseases (NIAID), with colleagues from academic institutions in Thailand, may offer fresh hope in this regard.
Through their research, they were able to show that a type of probiotic bacteria called Bacillus is able to fight and effectively eliminate S. aureus.
"Probiotics frequently are recommended as dietary supplements to improve digestive health," explains NIAID director Dr. Anthony S. Fauci.
"This is one of the first studies to describe precisely how they may work to provide health benefits. The possibility that oral Bacillus might be an effective alternative to antibiotic treatment for some conditions is scientifically intriguing and definitely worthy of further exploration."
Dr. Anthony S. Fauci
The effectiveness of Bacillus strains
In the new study — the results of which are now reported in the journal Nature — the researchers worked with 200 participants recruited from rural areas in Thailand.
They hypothesized that this population would, most likely, be less exposed to antibiotics or food sterilization.
First, the scientists collected and analyzed fecal samples from every person to try to identify which bacterial populations might be associated with an absence of S. aureus. This, they thought, would help them pinpoint the bacteria which stops S. aureus from colonizing.
They saw that 101 stool samples contained the probiotic Bacillus and, in particular, Bacillus subtilis. Bacillus bacteria are good at surviving in harsher environments, and they can be ingested with greens and vegetables. Bacillus also feature, together with other "good" bacteria, in several probiotic products.
When the researchers collected more samples from both the gut and the nose and tested them for the presence of S. aureus, they noted that the samples that contained Bacillus did not feature S. aureus and vice versa.
The scientists also conducted some tests in mice, which showed them that S. aureus bacteria have a specialized system that allows them to colonize and grow.
However, all Bacillus isolates that the scientists had removed from human fecal samples were able to effectively inhibit that specialized system.
By using techniques that let them analyze the components and activity of bacteria, the researchers found that Bacillus bacteria inhibited the specialized S. aureus system by producing molecules known as "fengycins."
Also, they noticed that fengycins inhibited the growth of many S. aureus strains, including USA300 MRSA, the potent superbug that is responsible for most of the threatening S. aureus community-associated infections in the U.S.
Promising results in mouse models
In further experiments conducted in mice, the scientists introduced S. aureus into the rodents' guts and allowed the bacteria to colonize these environments. Then, they fed the mice B. subtilis spores.
The rodents that received this treatment once every other day soon became free of S. aureus in their guts.
However, this effect was not seen in mice that were fed Bacillus in which fengycin production had been inhibited.
In the future, the researchers aim to conduct more experiments to see whether probiotic products that only feature B. subtilis are able to destroy S. aureus infections in humans.
"Ultimately, we hope to determine if a simple probiotic regimen can be used to reduce MRSA infection rates in hospitals," says the study's lead investigator, Michael Otto.