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Background and Objectives: Hospital-acquired infections (HAIs) and multidrug resistant bacteria pose a significant threat to the U.S. healthcare system. With a dearth of new antibiotic approvals, novel antimicrobial strategies are required to help solve this problem. Violet-blue visible light (400-470 nm) has been shown to elicit strong antimicrobial effects toward many pathogens, including representatives of the ESKAPE bacterial pathogens, which have a high propensity to cause HAIs. However, phototherapeutic solutions to prevention or treating infections are currently limited by efficient and nonobtrusive light-delivery mechanisms., Study Design/materials and Methods: Here, we investigate the in vitro antimicrobial properties of flexible Corning® light-diffusing fiber (LDF) toward members of the ESKAPE pathogens in a variety of growth states and in the context of biological materials. Bacteria were grown on agar surfaces, in liquid culture and on abiotic surfaces. We also explored the effects of 405 nm light within the presence of lung surfactant, human serum, and on eukaryotic cells. Pathogens tested include Enterococcus spp, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp., Staphylococcus epidermidis, Streptococcus pyogenes, Candida albicans, and Escherichia coli., Results: Overall, the LDF delivery of 405 nm violet-blue light exerted a significant degree of microbicidal activity against a wide range of pathogens under diverse experimental conditions., Conclusions: The results exemplify the fiber's promise as a non-traditional approach for the prevention and/or therapeutic intervention of HAIs. Lasers Surg. Med. © 2019 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc., (© 2019 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.)

Background and Objectives: One of the main advantages of laser surgery is it's bactericidal effect which reduces the risk of postoperative infections. Several study designs have been set to investigate this effect. Aim of this study was to research if the bactericidal effect of laser tool was affected from several factors in vitro studies., Study Design/materials and Methods: To determinate and investigate the bactericidal effect of laser in an original model, alpha-hemolytic streptococcus, Bacterioides fragilis, Neisseria, Streptococcus salivarius, Staphylococcus aureus, and Candida albicans were prepared in 10(4), 10(6) and 10(8) inoculum and placed in Mueller-Hinton Broth which have five different proportions of sheep blood. Samples which exposed with various energy levels of Nd:YAG laser were spread on agar plates, and at the end of an incubation time the colonization counted comparatively. The lowest energy level without colonization was accepted as minimal bactericidal energy level., Results: Highest minimum bactericidal energy level is used for alpha-hemolytic streptococcus and lowest values for neisseria. Bactericidal effect decreased on suspensions, of which population of microorganisms are high and hemoglobin concentration was high in the broth., Conclusions: These findings suggest that the Nd:YAG laser has a higher bactericidal effect when sheep blood is added to the media. Factors like population and type of bacteria in the irradiated suspension affect minimum bactericidal energy level., (Copyright 2003 Wiley-Liss, Inc.)

Background and Objectives: The difference in the photobactericidal efficacy of methylene blue and toluidine blue against gram-negative bacteria may result from their primary reaction with lipopolysaccharides (LPS) of the outer bacterial membrane. The aim of the present study was to compare the reactivity of these dyes with LPS extracted from different gram-negative bacteria., Study Design/materials and Methods: The interactions of methylene blue and toluidine blue with LPS from Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Klebsiella pneumoniae (K. pneumoniae), and Serratia marcescens (S. marcescens) were studied spectrophotometrically in 0.45% saline. The dyes were used at the concentration of 10 microM. The concentrations of LPS ranged from 5-100 microg/ml., Results: Methylene blue and toluidine blue enter into a metachromatic reaction with the LPS resulting the in generation of dimers of methylene blue and higher aggregates of toluidine blue. The more significant hypochromic and hypsochromic effects in the reaction of the latter with LPS indicate a greater metachromatic efficacy of toluidine blue than methylene blue. The equilibrium constants of the metachromatic complex between toluidine blue and different LPS were calculated. The spectrophotometric titration of LPS with the dyes was used to estimate the equivalent weight of LPS., Conclusions: Toluidine blue interacts with LPS more significantly than methylene blue in vitro. This may be one of the main factors determining its greater photobactericidal efficacy against gram-negative bacteria., (Copyright 2003 Wiley-Liss, Inc.)