Due to the rise in antibiotic resistance alternative antimicrobial approaches are being intensively investigated. It has been discovered that many microbial bacteria are susceptible to being killed by blue light in the region of 405-nm probably because the bacteria accumulate photoactive porphyrins. We have explored the ability of blue light to treat mouse models of wound and burn infections by such pathogens as Pseudomonas aeruginosa and methicillin resistant Staphylococcus aureus (MRSA).

Helicobacter pylori infection in the stomach causes peptic ulcers and gastric cancer. Antibiotic therapy leads to eighty percent eradication, but has side effects and has met increasing antibiotic resistance. We have discovered that H. pylori is susceptible to killing by visible light. Violet light is most effective (six log10 of killing). We have shown that both the bacterial pellets and culture supernatant accumulate significant amounts of the photoactive porphyrins, coproporphyrin and protoporphyrin that “leak” from the heme biosynthesis pathway. Multi-antibiotic resistant strains are also easily killed by light.

Two clinical trials in collaboration with LumeRx Inc. have been conducted. A Phase I clinical trial carried out endoscopy with a one-square-centimeter site in the pyloric antrum exposed to 405-nm violet light (140-mW/cm2, 40-J). Biopsies were taken from the control and illuminated sites and showed killing of >90% of bacteria (2-tailed p<0.0001). Some patients had bacterial killing approaching 99%.

A second clinical trial was conducted using a novel laser-diode catheter system to safely deliver 405-nm light to the whole human stomach. The system was first tested for safety in pig stomachs. Patients received whole stomach illumination at endoscopy with violet light at escalating total fluences. Significant bacterial killing was found as judged by quantitative culture from biopsies, and some patients have a negative urea breath test for a period, indicating temporary eradication.

Related Publications
Hamblin MR, Viveiros J, Yang C, Ahmadi A, Ganz, RA, Tolkoff MJ.  Helicobacter pylori accumulates photoactive porphyrins and is killed by visible light. Antimicrob Agents Chemother,  2005: 49(7): 2822–2827.

Ganz, RA. Viveiros J, Ahmad A, Ahmadi A, Khalil A Tolkoff MJ, Nishioka NS, Hamblin MR.Helicobacter pylori in patients can be killed by visible light. Lasers Surg Med 2005; 36(4): 260-5.

Lembo AJ, Ganz, RA, Sheth S, Cave D, Kelly C, Levin P, Kazlas PT,  Baldwin PC 3rd, Lindmark WR, McGrath JR, Hamblin MR. Treatment of Helicobacter pylori infection with intra-gastric violet light phototherapy – a pilot clinical trial. Lasers Surg Med, 2009. 41(5):337-344.

Dai T, Gupta A, Murray CK, Vrahas MS, Tegos GP, Hamblin MR. Blue light for infectious diseases: Propionibacterium acnes, Helicobacter pylori, and beyond? Drug Resist Updat. 2012, Aug;15(4):223-36.

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