title: Red and infrared laser therapy inhibits in vitro growth of major bacterial species that commonly colonize skin ulcers.
abstract: Low-level laser therapy (LLLT) is used in chronic wounds due to its healing effects. However, bacterial species may colonize these wounds and the optimal parameters for effective bacterial inhibition are not clear. The aim of this study was to analyze the effect of LLLT on bacterial growth in vitro. Bacterial strains including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were suspended in saline solution at a concentration of 10(3) cells/ml and exposed to laser irradiation at wavelengths of 660, 830, and 904 nm at fluences of 0 (control), 3, 6, 12, 18, and 24 J/cm(2). An aliquot of the irradiated suspension was spread on the surface of petri plates and incubated at 37 °C for quantification of colony-forming unit after 24, 48, and 72 h. Laser irradiation inhibited the growth of S. aureus at all wavelengths and fluences higher than 12 J/cm(2), showing a strong correlation between increase in fluence and bacterial inhibition. However, for P. aeruginosa, LLLT inhibited growth at all wavelengths only at a fluence of 24 J/cm(2). E. coli had similar growth inhibition at a wavelength of 830 nm at fluences of 3, 6, 12, and 24 J/cm(2). At wavelengths of 660 and 904 nm, growth inhibition was only observed at fluences of 12 and 18 J/cm(2), respectively. LLLT inhibited bacterial growth at all wavelengths, for a maximum of 72 h after irradiation, indicating a correlation between bacterial species, fluence, and wavelength.
authors.affiliation: Postgraduate Program in Rehabilitation and Functional Performance, Department of Biomechanics, Medicine, and Rehabilitation of the Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Natanael Teixeira Alves
authors.initials: NT
authors.lastname: de Sousa
authors.affiliation: Postgraduate Program in Rehabilitation and Functional Performance, Department of Biomechanics, Medicine, and Rehabilitation of the Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Rosana Caetano
authors.initials: RC
authors.lastname: Gomes
authors.affiliation: Graduation Course in Physiotherapy, Department of Biomechanics, Medicine, and Rehabilitation of the Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Marcos Ferracioli
authors.initials: MF
authors.lastname: Santos
authors.affiliation: Postgraduate Program in Rehabilitation and Functional Performance, Department of Biomechanics, Medicine, and Rehabilitation of the Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Hugo Evangelista
authors.initials: HE
authors.lastname: Brandino
authors.affiliation: Infectious Diseases Division of the Internal Medicine Department, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Roberto
authors.initials: R
authors.lastname: Martinez
authors.affiliation: Postgraduate Program in Rehabilitation and Functional Performance, Department of Biomechanics, Medicine, and Rehabilitation of the Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil. rguirro@fmrp.usp.br.|Graduation Course in Physiotherapy, Department of Biomechanics, Medicine, and Rehabilitation of the Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil. rguirro@fmrp.usp.br.|Department of Biomechanics, Medicine and Rehabilitation of the Locomotor System, Ribeirão Preto School of Medicine, University of São Paulo, 3900, Bandeirantes Avenue, Monte Alegre, Ribeirão Preto, SP, Brazil, CEP 14.049-900. rguirro@fmrp.usp.br.
authors.forename: Rinaldo Roberto
authors.initials: RR
authors.lastname: de Jesus Guirro
mesh_terms: D004926:Escherichia coli / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D007259:Infrared Rays; D028022:Low-Level Light Therapy; D011550:Pseudomonas aeruginosa / Q000502:physiology / Q000528:radiation effects*; D012883:Skin Ulcer / Q000382:microbiology* / Q000532:radiotherapy; D013211:Staphylococcus aureus / Q000502:physiology / Q000528:radiation effects*; D014945:Wound Healing
keywords: Escherichia coli; Low-level laser therapy; Pseudomonas aeruginosa; Skin ulcers; Staphylococcus aureus