Scientists tested a new type of helpful bacteria called S. salivarius eK12 that was designed to prevent strep throat infections in children. This modified bacteria comes from a well-studied probiotic strain that’s already used for oral health. Researchers gave the bacteria to rats in lab tests and checked for any harmful effects like genetic damage, poisoning, or organ problems. The results showed the bacteria was safe—it didn’t cause any damage, didn’t make the animals sick, and didn’t cause any concerning changes in their blood or organs. This is good news because it means this new probiotic could potentially help prevent strep throat without the side effects that come from overusing antibiotics.

The Quick Take

  • What they studied: Whether a genetically modified probiotic bacteria (a helpful microorganism) called S. salivarius eK12 is safe to use as a dietary supplement to prevent strep throat infections
  • Who participated: Laboratory tests using bacteria strains and safety studies in rats (both female and male rats of different ages), following strict international safety testing guidelines
  • Key finding: The modified bacteria showed no signs of being harmful—it didn’t cause genetic damage, didn’t poison the animals, and didn’t create any abnormal changes in blood work or organ tissue, even at very high doses
  • What it means for you: This probiotic may eventually offer a safer alternative to repeated antibiotics for preventing strep throat, though more human testing is needed before it becomes available. It appears to be as safe as its parent strain, which has been used safely for years

The Research Details

This was a comprehensive safety evaluation study that followed international testing standards (OECD guidelines) used worldwide to check if new substances are safe. The researchers conducted three types of tests: First, they tested whether the bacteria could cause genetic mutations using a standard lab test called the Ames test with five different bacterial strains. Second, they gave a single large dose to rats to check for immediate toxic effects. Third, they gave rats repeated doses over 90 days to see if long-term exposure caused any problems, then watched some rats for an additional 28 days after stopping treatment to check for delayed effects.

The rats were divided into different groups receiving either no bacteria (control group) or low, medium, or high doses of the modified bacteria. Scientists measured everything carefully: they watched for signs of illness, took blood samples to check for abnormalities, examined organs under a microscope, and looked for any behavioral changes.

This type of testing is the gold standard for determining if new food supplements or probiotics are safe before they’re tested in humans. By following these established protocols, the researchers could confidently say whether the bacteria posed any health risks.

This research matters because strep throat is a common childhood infection usually treated with antibiotics, but overusing antibiotics creates a serious public health problem—bacteria become resistant to these medicines, making infections harder to treat. If a safe probiotic could prevent strep throat, it would reduce unnecessary antibiotic use. However, before testing this new bacteria in people, scientists must first prove it won’t cause harm. This study provides that crucial safety foundation.

This study followed strict international safety testing standards (OECD guidelines) that are recognized worldwide, which makes the results reliable. The researchers tested multiple aspects of safety (genetic damage, acute toxicity, and long-term effects) rather than just one. They included recovery groups to check for delayed problems. The study was published in a peer-reviewed scientific journal, meaning other experts reviewed the work before publication. However, this was animal testing, so results don’t guarantee the same safety in humans—that would require separate human trials.

What the Results Show

The modified bacteria (S. salivarius eK12) passed all safety tests with no concerning findings. In the genetic mutation test, the bacteria did not cause any mutations in any of the five bacterial strains tested, even when the lab added enzymes to simulate how the body processes substances. This means it’s unlikely to cause genetic damage.

When rats received a single very large dose (equivalent to about 2,000 mg per kilogram of body weight), none of the animals died or showed signs of poisoning. They behaved normally and showed no physical problems. In the 90-day repeated-dose study, rats received the bacteria daily for three months at low, medium, or high doses. Throughout this period, the researchers found no treatment-related abnormalities in clinical observations, blood tests, or organ tissue examination under a microscope.

The minor variations in blood values and other measurements that did occur were small, random, and not connected to the dose level—meaning they weren’t caused by the bacteria. The recovery groups (rats that stopped receiving the bacteria and were observed for 28 more days) showed no delayed or lingering effects, confirming that any minor changes reversed naturally.

The study established a ’no observed adverse effect level’ (NOAEL) of 2,000 mg/kg per day, which is the highest dose tested where no harmful effects were seen. This is important because it gives scientists a reference point for determining safe doses in future human studies. The bacteria maintained the safety profile of its parent strain (the original K12 bacteria), suggesting that the genetic modifications made to enhance its anti-strep activity didn’t introduce new safety concerns. All organ systems examined—liver, kidneys, heart, lungs, and digestive system—appeared normal in all groups.

The original S. salivarius K12 bacteria has been extensively studied and used safely in probiotics for years. This new modified version (eK12) was created by adding genetic material to make it better at fighting strep bacteria. This study shows that the modification didn’t make it less safe—it retained the favorable safety profile of the original strain. This is reassuring because it means scientists successfully enhanced the bacteria’s beneficial properties without introducing new risks.

This study tested the bacteria in animals (rats), not humans, so we can’t be completely certain the same safety profile will apply to people until human trials are conducted. The study didn’t test long-term effects beyond 90 days, so we don’t know about safety with use over years. The study also didn’t test the bacteria in people with specific health conditions or taking certain medications, so safety in those populations remains unknown. Additionally, this study only evaluated safety—it didn’t measure whether the bacteria actually prevents strep throat in real-world conditions.

The Bottom Line

Based on this research, S. salivarius eK12 appears safe for further development and human testing (moderate confidence). The safety data supports moving forward with clinical trials in people. However, people should not expect this to be available as a consumer product immediately—additional human studies are required first. If and when it becomes available, it may be a useful option for people seeking to reduce strep throat infections without relying solely on antibiotics (moderate confidence).

Parents of children who get frequent strep throat infections should care about this research, as it could eventually offer a preventive option. Healthcare providers treating recurrent strep throat should follow this development. People concerned about antibiotic resistance should find this promising. However, this research doesn’t yet apply to anyone—it’s a preliminary safety study, not a treatment recommendation. People currently dealing with strep throat should continue using antibiotics as prescribed by their doctor.

This is very early-stage research. Even if human trials begin soon, it typically takes 3-5 years to complete safety and effectiveness studies in people. If successful, regulatory approval could take another 1-2 years. Realistically, this probiotic wouldn’t be available to consumers for at least 5-7 years, possibly longer. This timeline allows for thorough testing to ensure it works as intended.

Want to Apply This Research?

  • Once available, users could track strep throat infections monthly: record the date of any sore throat diagnosis, whether it tested positive for strep, and any antibiotic use. Compare infection frequency before and after starting the probiotic over a 6-12 month period.
  • When this probiotic becomes available, users could set a daily reminder to take it consistently, similar to a vitamin routine. Track compliance by logging each dose taken. Pair this with other preventive habits like handwashing and avoiding close contact with people who have strep throat.
  • Track quarterly metrics: number of strep throat infections per quarter, antibiotic courses needed, and any digestive side effects. Create a simple chart showing infection trends over 6-12 months to see if the probiotic is working for your family. Share this data with your doctor to help determine if it’s effective for you personally.

This research describes laboratory and animal safety testing only—it does not prove the bacteria is safe or effective in humans. S. salivarius eK12 is not currently available as a consumer product and has not been approved by regulatory agencies like the FDA. This study does not constitute medical advice. Anyone with recurrent strep throat should consult their healthcare provider about current treatment options. Do not delay or replace antibiotic treatment for active strep throat infections based on this research. Future human studies are needed before this probiotic can be recommended for clinical use. Always consult a healthcare provider before starting any new supplement or probiotic, especially for children or if you have underlying health conditions.