Blue Light, Food Oils Combo Kills Superbugs, says Study

February 24, 2021
Frank Diamond

Infection Control Today, Infection Control Today, April 2021 (Vol. 25 No.3), Volume 25, Issue 03

Investigators wanted to see how their method would fare against Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus, and results were promising.

As Ravi Starlz, PhD, told Infection Control Today® in December,1 when it comes to humanity’s battle against bacterial infections, the bacteria have a head start. “If you’re constantly focused on trying to escalate the war of destruction, I think that the bacteria will always win that war,” said Starlz, an adjunct professor at Carnegie Mellon University. “They just have too many countermeasures available to them, and our rate of developing new antibiotics is far slower than their rate of developing countermeasures.”

Which brings to us to the problem that multidrug-resistant organisms (MDRO) pose to infection preventionists, and for that matter, to the entire health care system.

It’s a problem that investigators at Harvard Medical School and Shanghai Jiao Tong University School of Medicine hope will one day be solved, and that their work will have helped to solve it. Investigators say that surface bacteria can be illuminated using a blue light along with carvacrol, which is a phenolic monoterpenoid that can be found in oils made from oregano, thyme, pepperwort, wild bergamot, and other plants. It’s common, but also uncommon, in that it contains hydrophilic molecules and the phenol moiety. That combined with the blue light can effectively treat skin and soft tissue infections (SSTIs), according to their study in Science Translational Medicine.2

Investigators wanted to see how their method would fare against such MDROs as Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus. The 2-step process for SSTIs can also conceivably be used to treat patients with diabetes who suffer from wounds, the sort of wounds that are not always easily treated with antibiotics.

“A growing number of patients with compromised immunity, such as cancer and diabetic patients, invasive medical procedures, and the associated surgical site infections all have contributed to the increasing incidence of SSTI over the past decade,” the study states. “It has been suggested that the ability to control the surface of the wound contamination below 10 CFU/g of tissue is crucial to prevent sepsis, which might be achievable by blue light combined with carvacrol.”

According to the Centers for Disease Control and Prevention (CDC),3 MDROs infect about 2.8 million people in the United States each year, killing about 35,000 of them. The CDC says, “Dedicated prevention and infection control efforts in the US are working to reduce the number of infections and deaths caused by antibiotic-resistant germs, but the number of people facing antibiotic resistance is still too high. More action is needed to fully protect people.”

Disinfecting bacteria on a wound would probably lessen instances of nosocomial infections, according to the authors of the study in Science Translational Medicine. MDROs “are commonly colonized on the wound surface and openly exposed to the atmosphere, becoming one of the major sources for contaminating the health care environment and posing high risk to vulnerable patients to contract the bacteria in hospitals,” the study states. “Therefore, quick and efficacious eradication of surface wound bacteria could effectively minimize nosocomial infections.”

The blue light and carvacrol not only killed the bacteria, but also produced no adverse events to the animals used in the study. “We ascribe this safety profile to initiation of the phototoxic cascade reaction by blue light excitation of endogenous porphyrin-like molecules. These porphyrin-like molecules are primarily tetrapyrrole macrocycles—such as protoporphyrin, uroporphyrinogen III, coproporphyrinogen III, and coproporphyrin III—based on their absorbance and excitation spectra and ability to respond to blue light similarly as PPIX [protoporphyrin IX],” the study states. 


  1. Diamond F. Q&A: ‘It’s far worse than COVID’. Infection Control Today®. Published online December 28, 2020. Accessed March 1, 2021.
  2. Lu M, Wang S, Wang T, et al. Bacteria-specific phototoxic reactions triggered by blue light and phytochemical carvacrol. Sci Transl Med. 2021;13(575):eaba3571.doi:10.1126/scitranslmed.aba3571
  3. Centers for Disease Control and Prevention. Antibiotic/antimicrobial resistance; biggest threats and data. Accessed March 1, 2021.
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