Viruses that invade bacteria but leave human cells alone could help scientists find ways around the growing problem of antibiotic resistance, researchers have said.

A study has showed that a cocktail of bacteriophages, or “phages”, resulted in no side effects when given to individuals with gastrointestinal problems and did not appear to greatly disrupt the diversity of microbes in the gut – the so-called gut microbiota. But they did reduce levels of one marker of inflammation and certain problematic species of bacteria.

“[Phages] are a wonderful alternative to antibiotics,” said nutrition blogger and scientific consultant Dr Taylor Wallace of George Mason University, Virginia, who is presenting the results of the study at the American Society for Nutrition annual meeting in Boston. “These are selective, you don’t have any problem with bacterial resistance … and they are safe.”



Experts say microbial resistance to antibiotics, largely fuelled by overuse and misuse of the drugs, has left the world facing “a dreadful post-antibiotic apocalypse” as such treatments become ineffective.

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The new research, funded by probiotic company Deerland Enzymes, split 32 participants, all of whom reported recurring gastrointestinal problems but were otherwise healthy, into two groups. One group was given a placebo capsule for four weeks, the other group was given a capsule from the company containing four phage strains expected to attack E coli. Neither the participants nor the researchers knew which capsules were given to whom during the trial.

After four weeks both groups stopped taking their capsules and, two weeks later, had their capsules swapped to the opposite type, which were then taken for a further four weeks.

The findings revealed that there were no side effects from taking the phages, but that the cocktail did appear to have some impact, including a drop in levels of a protein linked to inflammation and allergic response, and a drop in certain bacterial species that can cause problems, including Clostridium perfringens. “We saw some increases in beneficial bacteria,” added Wallace.



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However, the study, which has not yet been peer-reviewed, only looked at short-term use of phages and did not check whether E coli was behind the gut problems to start with.

What’s more, only some participants had experienced a drop in E coli – possibly, said Wallace, because they had had higher levels to begin with. And while some participants felt better and appeared to be able to tell when they had taken the phages, others noted no improvement.

Wallace said the findings highlighted how phages could be used to adjust the body’s communities of microbes to boost health, and offered an alternative to antibiotics in tackling potentially harmful bacteria.

Martha Clokie, professor of microbiology at the University of Leicester, welcomed the study, pointing out that while phages are commonplace in our bodies – and are currently used in food production, as well as medical treatments in some countries such as Georgia – clinical trials into their safety as therapeutics are necessary.

Clokie says phages could be valuable since they can be used to target particular bacteria that have caused infection or have knocked the body’s community of microbes out of kilter – a situation known as dysbiosis. Antibiotics by contrast often wipe out both “good” and “bad” microbes, which can cause problems. “Phages are very specific manipulators, they can take out certain species which can then allow the other ones, which are beneficial, to grow,” said Clokie.

Aras Kadioglu, professor of bacterial pathogenesis at the University of Liverpool, was also cautiously optimistic, although he noted the study had yet to be published. “The use of phages to correctly “balance” a disturbed gut microbiota [flora] following infection and or antibiotic treatment, for example, is really quite exciting,” he said.

Bacteriophages, Clokie adds, have been known about for more than a century. “Phages were used before we discovered antibiotics,” she said, adding their ability to target particular microbes was initially seen as a disadvantage. “Actually there are many aspects of disease where that specificity is now useful to us.”