Blue light rescues mice from potentially fatal Pseudomonas aeruginosa burn infection: efficacy, safety, and mechanism of action.
Antimicrob Agents Chemother. 2012 Dec 21.
Dai T, Gupta A, Huang YY, Yin R, Murray CK, Vrahas MS, Sherwood M, Tegos GP, Hamblin MR.
Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA.
Blue light has attracted increasing attention due to its intrinsic antimicrobial effect without the addition of exogenous photosensitizers. However, the use of blue light for wound infections has not been established yet. In this study, we demonstrated the efficacy of blue light at 415 nm for treatment of acute, potentially lethal Pseudomonas aeruginosa burn infections in mice. In vitro studies demonstrated that the inactivation rate of P. aeruginosa cells by blue light was approximately 35-fold faster than that of keratinocytes (P=0.0014). Transmission electron microscopy revealed blue light mediated intracellular damage to P. aeruginosa cells. Fluorescence spectroscopy suggested that coproporphyrin III or/and uroporphyrin III are possibly the intracellular photosensitive chromophores associated with the blue light inactivation of P. aeruginosa. In vivo studies using an in vivo bioluminescence imaging technique and the area-under-the-bioluminescence-time-curve (AUBC) analysis showed that a single exposure of blue light at 55.8 J/cm(2), applied 30 min after bacterial inoculation to the infected mouse burns, reduced the AUBC by an approximately 100-fold in comparison with untreated and infected mouse burns (P<0.0001). Histological analysis and TUNEL assay indicated no significant damages in the mouse skin exposed to blue light at the effective antimicrobial dose. Survival analysis revealed that blue light increased the survival rate of infected mice from 18.2% to 100% (P<0.0001). In conclusion, blue light therapy may offer an effective and safe alternative to conventional antimicrobial therapy for P. aeruginosa burn infections.
Blue light can selectively eradicate Pseudomonas aeruginosa infections of the skin and soft tissues, while preserving the outermost layer of skin, according to a proof-of-principle study led by Michael R. Hamblin of the Massachusetts General Hospital, and the Harvard Medical School, Boston. The research is published online ahead of print in the journal Antimicrobial Agents and Chemotherapy
"Blue light is a potential non-toxic, non-antibiotic approach for treating skin and soft tissue infections, especially those caused by antibiotic resistant pathogens," says Hamblin.
In the study, animal models were infected with P. aeruginosa. All of the animals in the group treated with blue light survived, while in the control, 82 percent (9 out of 11) of the animals died.
Skin and soft tissue infections are the second most common bacterial infections encountered in clinical practice, and represent the most common infection presentation—more than 3 percent—in patients visiting emergency departments,says Hamblin. The prevalence of skin and soft tissue infections among hospitalized patients is 10 percent, with approximately 14.2 million ambulatory care visits every year and an annual associated medical cost of almost $24 billion (equivalent to $76 for every American), says Hamblin.
Treatment of skin and soft tissue infections has been significantly complicated by the explosion of antibiotic resistance, which may bring an end to what medical scientists refer to as the antibiotic era, says Hamblin. "Microbes replicate very rapidly, and a mutation that helps a microbe survive in the presence of an antibiotic drug will quickly predominate throughout the microbial population. Recently, a dangerous new enzyme, NDM-1, that makes some bacteria resistant to almost all antibiotics available has been found in the United States. Many physicians are concerned that several infections soon may be untreatable."
Besides harming public health, antibiotic resistance boosts health care costs.
"Treating resistant skin and soft tissue infections often requires the use of more expensive, or more toxic drugs, and can result in longer hospital stays for infected patients," says Hamblin.
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