REVISÃO
Low laser therapy
(photobiomodulation) on bacteria of pressure ulcers: in vitro studies
Laser de baixa potência (fotobiomodulação) sobre
bacterias de úlceras de pressão: estudos in vitro
Andrezza Maria Côrtes Thomé*, Luiz Philippe da
Silva Sergio*, Marco Orsini**, Marcos RG de Freitas***, Silmar Teixeira****,
Victor Hugo Bastos****, Pedro Ribeiro*****, Adenilson de Souza da Fonseca*,
Acary Souza Bulle Oliveira******, Eduardo Tavares Lima Trajano**, José Teixeira
de Seixas Filho*******, Patrícia Maria Dusek*******
*Departamento
de Biofísica e Biometria, Instituto de Biologia Roberto Alcântara Gomes,
Universidade do Estado do Rio de Janeiro, UERJ, **Programa de Mestrado em
Ciências Aplicadas em Saúde, Universidade de Vassouras - USS, Programa de
Mestrado em Desenvolvimento Local – UNISUAM, Bonsucesso/RJ, ***Faculdade de
Medicina (Neurologia), Universidade Federal do Rio de Janeiro - UFRJ,
****Departamento de Fisioterapia Universidade Federal do Piauí, *****Instituto
de Psiquiatria, Laboratório de Mapeamento Cerebral e EEG, Universidade Federal
do Rio de Janeiro, ******Universidade Federal de São Paulo, Escola Paulista de
Medicina, UNIFESP, *******Programa de Mestrado em Desenvolvimento Local,
UNISUAM Bonsucesso/RJ
Resumo
Os
efeitos biológicos promovidos pelo laser de baixa potência resultam em
cicatrização mais rápida das feridas. No entanto, as feridas são sistemas muito
complexos, tanto do ponto de vista microbiano quanto do hospedeiro. Como a
infecção é uma causa comum de cicatrização retardada, é importante entender o
efeito da terapia com laser de baixa intensidade no crescimento bacteriano.
Esta mini-revisão resume as evidências atuais sobre os
efeitos do laser de baixa intensidade em estudos de bactérias in vitro.
Palavras-chave: laser de baixa
potência, lesão infectada, bactérias.
Abstract
The
biological effects promoted by low power laser result
in faster wound healing. However, wounds are very complex systems from both
host and microbial point of view. Since infection is a common cause of delayed
wound healing, it is important to understand the effect of low-level laser
therapy in bacterial growth. This mini-review summaries the current evidence
about effects of low level laser on bacteria vitro studies.
Key-words: Low power laser, infected injury, bacteria.
Chronic wounds include pressure injuries,
diabetic ulcers, venous ulcers, and arterial ulcers, and affect approximately
5-7 million people per year in the United States [1]. More recently, the cost
for the treatment of a single ulcer has increased to US$ 8000, and the cost of
an infected ulcer has increased to approximately US$ 17,000 per year. Global
wound care expenditures amount to US$ 13 to US$ 15 billion annually [2]. These
are very complex systems from both host and microbial point of view [3].
Infections of the dermis affect over a
million people, cause thousands of deaths and cost billions of dollars in direct
medical costs annually. The infection chronic wound care accounts for an
estimated cost of US$ 15 billion annually in the United States. In
underdeveloped nations and in areas of conflict the numbers are significantly
higher [4,5]. Infections caused by opportunistic bacterial pathogens are a
primary cause of morbidity and mortality in both the developed and developing
world [1].
It is now recognized that bacterial
infections are one of the main driving factors for the development of a chronic
wound [3]. Infection is known to extend the inflammatory phase and impair wound
healing, potentially causing pain, discomfort and distress for the patient [6].
Chronic nonhealing wound is one of the major
therapeutic and economic issues in medicine today. Currently, efforts are being
made to explore novel strategies, pharmacotherapeutic agents, bioactive
dressings, tissue engineered scaffolds, stem cell-based therapy as well as
drugless, noninvasive, biophysical therapeutic interventions using light-based
treatment (photobiomodulation, PBM, or low power
laser, LPL) [4].
The biological effects promoted by low power laser are related to the decrease in inflammatory
cells, increased fibroblast proliferation, angiogenesis stimulation, formation
of granulation tissue and increased collagen synthesis, which result in faster
wound healing [7].
Since infection is a common cause of delayed
wound healing, it is important to understand the effect of low-level laser
therapy in bacterial growth. This mini-review summaries the current evidence
about effects of low level laser on bacteria.
Bacteria are the most common reason for poor
wound healing and there is an increasing worldwide rise in antibiotic
resistance bacteria which calls for the development of novel antimicrobial
strategies, of which photobiomodulation is one approach that can be further
developed to avoid using ever more potent and potentially clinically toxic
antibiotics [7].
These infections are often characterized by
robust growth of the pathogen in the infection site and increasingly high
resistance to antibiotic treatment [1]. In addition, studies (using a
combination of traditional culture methods, microscopic analyses, and molecular
techniques) involving wound samples from human patients support the presence of
mixed populations of microorganisms in different types of chronic wounds [9].
Advances in molecular diagnosis have provided sensitive methods for identifying
microbes present in wounds and standard culturing techniques detected 12
different bacterial genera populating the wounds, molecular methods revealed up
to 106 different bacterial genera [5]. Staphylococcus
(S.) aureus, Escherichia (E.) coli,
and Pseudomonas (P.) aeruginosa were
commonly associated with wound infections.
Bacteria irradiated with continuous and
pulsed modes (810 nm, 0.015 W/cm²; 1–50 J/cm²) shows that bacterial growth
increased overall, independent of species, using continuous mode laser,
significantly so at 1 J/cm². Analysis of individual
species demonstrated that laser mediated growth of S. aureus and E. coli was dependent on pulse frequencies and pulsed mode
seems to have the potential to induce growth effects in P. aeruginosa that could seriously impact on wound healing [10].
Photobiomodulation at 810 nm, in continuous
mode, but in different irradiance of 0.015 W/cm² 1–50 J/cm² 0.03 W/cm² shows
that decreased growth of P. aeruginosa
and increased growth of E. coli, the effect being greater at irradiance of 0.03
W/cm² than with irradiance of 0.015 W/cm² for identical radiant exposures. S. aureus growth was not affected by
irradiation at either irradiance. Optimum bacterial inhibition was found at
radiant exposures of 20 J/cm² or less, regardless of irradiance and species
[11].
Strains of these bacteria were irradiated by
red (630 nm), infrared (904 nm), green (525 nm), blue
(465 nm), and UV (350 nm). Low power laser in this
study had no effect on bacteria growth. However, when used different fluences
(0-24 J/cm²) at wavelengths of 660, 830, and 904 nm, laser irradiation
inhibited the growth of S. aureus at
all wavelengths and fluences higher than 12 J/cm², showing a strong correlation
between increase in fluence and bacterial inhibition. However, for P. aeruginosa, low power
laser inhibited growth at all wavelengths only at a fluence of 24 J/cm². E. coli had
similar growth inhibition at a wavelength of 830 nm at fluences of 3, 6, 12,
and 24 J/cm². At wavelengths of 660 and 904 nm, growth inhibition was only
observed at fluences of 12 and 18 J/cm², respectively [12].
Irradiation on E.coli with red and infrared lasers at high fluences (250, 500 and
1000 J/cm²) is lethal, induce a filamentation phenotype, and alter the
morphology of the E. coli
cells. Low-intensity red and infrared lasers have potential to induce adverse
effects on cells, whether used at unusually high fluences, or at high doses [13]
Most bacterial pathogenesis studies have
focused on mono-culture infections; however, it is clear that many bacterial
infections are not simply the result of colonization with a single species, but
rather ensue from the action of polymicrobial communities, microorganisms are
social creatures that build complex communities such as biofilms. Microbes
within polymicrobial infections often display synergistic interactions that
result in enhanced colonization, persistence and antibiotic resistance in the
infection site [14].
A review about the use of low power laser to promote biofilm killing and wound healing,
conclude that lack of credible studies using reproducible models and light
dosimetry restricts the analysis of current data [16]. It was shown that the
laser treatment (NIR, 10 W, 148 J/cm²) has not affected the biofilms biomass
neither the cell viability, although a small disruptive action was observed in
the structure of all biofilms of Staphylococcus
aureus and Pseudomonas aeruginosa
[15]. A Pubmed search found no other data about biofilm formation induced by exposure to low power
laser at therapeutic fluencies associated with wound.
The variable characteristics and parameters
of light devices is one of the factors that complicate the interpretation of
research results about the effects of low power laser
on skin wounds. Low power laser inhibited bacterial growth
at high fluences and different wavelength, indicating a correlation between
bacterial species, fluences, and wavelength. However, some
protocols increased bacterial growth and induce adverse effects, hence, there
is a need to reinforce the importance of accurate dosimetry in therapeutic
protocols. In addition, it is necessary more studies about the effects of low power laser on polymicrobial communities, because microbial
communities can be highly spatially organized throughout the human body and
within sites of infection.