More than 35,000 people die each year in the US alone from antimicrobial resistant infections.1 With novel treatments in short supply, scientists plan to boost available therapies to target antimicrobial resistance. In a paper published in PNAS, researchers used the power of light to give antibiotics a fighting chance.2

“Everything I do with light is to kill,” said Vanderlei Bagnato, a physicist at Texas A&M University and the University of São Paolo, and coauthor of the paper. 

Light interacts with chemicals called photosensitizers to produce toxic reactive oxygen species.3 Unlike many antibiotics, photosensitizers can sneak past bacterial defenses. Bagnato’s team previously found that light, plus the photosensitizer curcumin, a chemical found in turmeric, potentiated antibiotic efficacy.4   

In their new study, Bagnato and his team tested whether light could resensitize drug-resistant bacteria to lower doses of antibiotics. They found that they needed to expose drug-resistant strains of Staphylococcus aureus to high doses of different antibiotics to curb pathogen growth. However, when Bagnato added the curcumin and shone light on the bacteria, a lower dose sufficed. For most strains, the effects were temporary; the team observed a recurrence in resistance after only a few cycles of bacterial growth. Next, Bagnato wants to dissect the mechanisms underlying the temporary resensitization. 

Tayyaba Hasan, an expert in photomedicine at Harvard Medical School, said that these findings line up with her own findings.3,5 However, she noted that Bagnato and his team only tested gram-positive bacteria. “The real problem is with the gram-negative [bacteria],” said Hasan, since it is harder for antibiotics to breach their outer membrane layers. 

Bagnato emphasized the need for alternative therapies. “Infection does not need one type of weapon; it needs a whole arsenal,” said Bagnato.


  1. CDC. Department of Health and Human Services, CDC;2019
  2. Soares JM, et al. Proc Natl Acad Sci USA. 2023;120(39):e2311667120.
  3. Hamblin MR, Hasan T. Photochem Photobiol Sci. 2004;3(5):436-450.
  4. Soares JM, et al. Sci Rep. 2022;12:21146.
  5. Feng Y, et al. Adv Drug Deliv Rev.  2021;177:113941.