Near‐infrared Photoinactivation of Bacteria and Fungi at Physiologic Temperatures

Abstract

We examined a laser system (870 and 930 nm), employing wavelengths that have exhibited cellular photodamage properties in optical traps. In vitro, with 1.5 cm diameter flat-top projections (power density of 5.66 W cm(-2)), at physiologic temperatures, we achieved photoinactivation of Staphylococcus aureus, Escherichia coli, Candida albicans and Trichophyton rubrum. Using nonlethal dosimetry, we measured a decrease in trans-membrane potentials (DeltaPsimt and DeltaPsip) and an increase in reactive oxygen species (ROS) generation in methicillin-resistant S. aureus (MRSA), C. albicans and human embryonic kidney cells. We postulate that these multiplexed wavelengths cause an optically mediated mechano-transduction of cellular redox pathways, decreasing DeltaPsi and increasing ROS. The cellular energetics of prokaryotic and fungal pathogens, along with mammalian cells, are affected in a similar manner when treated with these multiplexed wavelengths at the power densities employed. Following live porcine thermal tolerance skin experiments, we then performed human pilot studies, examining photodamage to MRSA in the nose and fungi in onychomycosis. No observable damage to the nares or the nail matrix was observed, yet photodamage to the pathogens was achieved at physiologic temperatures. The selective aspect of this near-infrared photodamage presents the possibility for its future utilization in human cutaneous antimicrobial therapy.

Effects of near-infrared laser radiation on the survival and inflammatory potential of Candida spp. involved in the pathogenesis of chemotherapy-induced oral mucositis

“…The generation of reactive oxygen species (ROS), resulting from the absorption of laser radiation at the mitochondrial level, has been proposed as a major molecular mechanism underlying the photoinactivating action of laser therapy on microbial species, including C. albicans and Staphylococcus [9]. Indeed, increased ROS generation might be responsible for the induction of apoptosis observed in our experiments.…”

“…In these studies, treatments have been performed by using a wide range of sources, differing in power (class I-III lasers, with power lower than 0.5 W, and class IV lasers, with power higher than 0.5 W), wavelength [mostly in the red and nearinfrared (NIR) bands], and emission (single and combined, continuous and pulsed mode). Although some studies reported an increase in the mortality of C. albicans in vitro [7][8][9], the molecular and cellular mechanisms underlying the effects of laser therapy on microorganisms and host tissues remain largely unknown. Recently, the effects of two treatment protocols differing in wavelength (λ 635 nm versus λ 970 nm) and energy density (0.375 J/cm 2 versus 375 J/cm 2 ) have been studied and compared in an animal model of chemotherapyinduced OM.…”

Novel light therapies in treatment of onychomycosis

“…Bornstein i wsp. [31] wykazali ich skuteczność in vitro i in vivo w stosunku do C. albicans i T. rubrum, w temperaturze fizjologicznej, niepowodującej uszkodzenia tkanek gospodarza. Szersze badania kliniczne z wykorzystaniem lasera wytwarzającego fale o długościach 870 nm i 930 nm opublikowali Landsman i wsp.…”

“…Na możliwości rozwoju zastosowania terapii fotodynamicznej w leczeniu grzybicy paznokci wskazują również ostatnie publikacje dotyczące poszukiwania nowych, lepszych substancji o działaniu fotouczulającym przeznaczonych do terapii grzybicy paznokci [31].…”

All you need is light

“…87 It has been shown that near-infrared light can cause selective photodamage of multidrug-resistant pathogens. 88 In a recent study, it has been demonstrated that photodamage of multidrug-resistant Gram-positive and Gram-negative bacteria by near-infrared (870 nm/930 nm) light potentiates erythromycin, tetracycline and ciprofloxacin. 89 Although the antibiotics used in this study are MES substrates and therefore it is reasonable to assume that near infrared light may play role in efflux inhibition the experimental evidence is rather weak and this possibility requires further exploration.…”