Antibiotic neomycin may protect against the flu, COVID-19

By Staff 9 Min Read

  • Viral respiratory infections are common and generally result in a few days of illness from which most people recover without treatment.
  • However, they can lead to severe disease, so most existing treatments aim to prevent existing infections from progressing.
  • A new study suggests a way of stopping viral respiratory infections before they have a chance to become severe.
  • The study found that a common antibiotic boosts the immune response to both SARS-CoV-2 and influenza in rodents, preventing severe disease and death.
  • The researchers propose that the antibiotic, neomycin, could be a cheap, effective way to prevent and treat viral respiratory infections in people.

The COVID-19 pandemic focused attention on viral respiratory infections and how they can be prevented and treated.

With effective vaccines against SARS-CoV-2 — the virus that causes COVID-19 — severe disease is less common than it was at the start of the pandemic, but there are still few effective treatments for this and other viral respiratory infections.

Currently, doctors use antivirals to try and prevent progression of these infections, with monoclonal antibodies and convalescent plasma for combating severe disease.

Now, a study led by researchers from Yale has found that a cheap, widely available antibiotic might reduce the risk of severe disease from viral respiratory infections.

The study found that neomycin, applied inside the nose, caused a strong immune response in mice and hamsters which protected against infection with both SARS-CoV-2 and influenza A.

And a small group of healthy people treated with a common nasal ointment containing neomycin — Neosporin — showed a similar immune response.

The study is published in PNAS.

William Schaffner, MD, professor of preventive medicine in the Department of Health Policy, and professor of medicine in the Division of Infectious Diseases at Vanderbilt University Medical Center, Nashville, TN, not involved in the study, commented on the findings for Medical News Today:

“This is a very provocative study. Clearly, there is an urgent need for better ways both to prevent and to treat serious respiratory infections. This series of early studies suggests that non-specific immune stimulation by an over-the-counter antibiotic ointment could protect the mucus membranes of the nose from viral infection. This is a fascinating counter-intuitive concept that is worth pursuing further.”

Antibiotics are drugs that kill bacteria and/or prevent them from multiplying. They are used to treat bacterial infections inside the body and also as topical treatments for infections of the skin.

Neomycin is an aminoglycoside antibiotic. People take it orally for infections in the digestive tract, or can use it as a topical ointment, neosporin.

Neosporin ointment, which contains neomycin and two other antibiotics, is used to prevent infection in minor cuts and burns, for bacterial infections of the nose, and for management of nosebleeds.

The researchers in this study investigated whether intranasal application of neomycin evoked antiviral protection against SARS-CoV-2 and influenza A in the upper respiratory tract of mice and whether it prevented transmission of SARS-CoV-2 in hamsters.

Jonathan Stoye, PhD, virologist and principal group leader at the Francis Crick Institute in London, United Kingdom, not involved in this research, explained to MNT:

“The concept of preventing virus infection by stimulating natural antiviral immunity has enormous appeal.”

First, the researchers treated mice with a single dose of 2 milligrams (mg) neomycin sulfate as 10 microliters (μL) of neomycin solution per nostril. They euthanized mice on days 1, 3, 5, and 7 after neomycin treatment and collected nasal tissue for analysis.

From day 1, the neomycin-treated mice had significantly increased levels of interferon-stimulated gene (ISG) expression — an immune response that is effective against viruses — compared with controls.

The researchers then infected neomycin-treated transgenic (genetically engineered) mice with different strains of SARS-CoV-2.

The mice did not show the usual signs of infection, such as weight loss, and most survived the infection, whereas the control mice did not. Nasal cells from the neomycin-treated mice showed significantly lower levels of viral replication than those of control mice.

Neomycin-treated mice had a similar increase in resistance to influenza A infection.

The researchers treated Syrian hamsters with intranasal neomycin (5 mg) then housed them with hamsters that had been infected 24 hours earlier with SARS-CoV-2. One day later, only half of the neomycin-treated hamsters had any signs of infection.

“This early-stage research in several rodent models identifies one compound, neomycin, that appears to have [antiviral] activity,” Stoye told MNT.

However, Schaffner cautioned that findings in rodents might not be applicable to people. “It is a long jump from animal studies to use in humans. This study represents the first steps in a long journey,” he said.

The researchers then conducted a small, double-blind pilot study in people. A group of 12 healthy volunteers was treated with Neosporin ointment, which contains neomycin sulfate, bacitracin, and polymyxin B as its active ingredients.

They applied the ointment inside their nostrils using a cotton swab twice a day. Control volunteers applied petroleum jelly (Vaseline) in the same way.

When their immune responses were tested on days 4, 8 and 12 of the trial, the Neosporin-treated group had a much higher ISG response rate than the controls.

“Although an immune response in human volunteers was elicited by the intranasal application of Neosporin ointment, whether this would prevent or treat viral infections in people will have to be demonstrated in a prospective, double-blind trial in a large group of volunteers,” cautioned Schaffner.

“Early results always are exciting, but much more work is needed before we can consider this for clinical application,” Schaffner noted.

Using antivirals to treat infections can drive the development of resistant strains as respiratory viruses mutate rapidly, so the researchers suggest that stimulating the innate immune response using antibiotics could be an effective alternative treatment.

The researchers also point out that neomycin is cheap, readily available, and easy to administer intranasally.

However, both Schaffner and Stoye had concerns about using neomycin in this way.

Schaffner told us:

“In order to prevent SARS-CoV-2 or any respiratory viral infection, patients likely would have to apply the Neosporin ointment to the nose for very long periods of time. Whether persons would be compliant with such a regimen would have to be determined. Also, the safety of such prolonged application of the ointment to the nasal mucus membranes would have to be established.”

He also highlighted the risks of using any antibiotic for prolonged periods: “In addition, there is the concern that the widespread and prolonged use of the antibiotic ointment could provoke the development of antibiotic resistance of the usual bacterial population of the nose and throat. If so, this would be a notable limitation.”

While welcoming the study, Stoye called for further research into the treatment. “Much more work will be required to determine how it works, whether it is protective in humans and whether it would be safe to use on the population level,” he noted.

Share This Article
Leave a comment