Evaluation of the effectiveness of different doses from alexandrite laser on Staphylococcus aureus bacteria growth in vitro

By Elaf Ahmed Mustafa

2018

Summary
Background: Laser is a novel physical therapy technique used to treat a variety of conditions, including wound healing, inhibition of bacterial growth, and postoperative wounds. High-Power pulsed alexandrite laser therapy is one of the most prevalent forms of laser therapy, which is a noninvasive method for treating a variety of pathological conditions, thereby enhancing functional capacities and quality of life. It is a modern medical and physiotherapeutic technology. Generally, the Alexandrite laser emits infrared light with a wavelength of 755 nm, allowing it to propagate and penetrate tissues.
Objective: The study focused on the application of a high-power pulsed alexandrite laser in vitro to evaluation the effect of a pulsed alexandrite laser on antibiotic-resistant bacteria utilizing varying exposure times, pulse durations, and laser fluencies to determine which dose is more effective on Staphylococcus aureus bacteria>
Method: The laser system was fixed vertically on mechanical jack supported with height tuner screw on plane bench; so the laser beam can fall vertically on the test sample and the laser aperture was stick to the test sample. The alexandrite laser that was used in the study which was considered as pulsed laser and had the following
parameters: The wavelength was 755 nm, the beam diameter was (14 mm), the exposure times varied (30, 60, 90) seconds, the laser fluency (5, 10, 15 and 20 J.cm⁻²) and pulsed duration (5 , 10 , 20 ms ). The study was carried out after the bacteria were diagnosed as being resistant to antibiotics, they were exposed to different doses of Alexandrite laser. Three isolates of bacteria were exposed to laser beams for 30 seconds with a 5ms of pulse duration and with a laser fluency of 5J/cm2 and the process were repeated with laser fluencies of 10, 15, and 20. The procedure was repeated using exposure times of 60sec and 90sec. As well as, the process was repeated by expose with 30 sec, 60 sec and 90 sec exposure times, 10ms pulse duration and with laser fluencies 5, 10, 15 and 20J/cm², II separately. Also, the previous process was repeated by expose the bacteria with different exposure times (30 sec, 60 sec and 90 sec), 20ms pulse duration and with different laser fluencies (5, 10, 15 and 20J/cm²), separately. Results: At 30, 60 and 90 sec exposure times, there are significant reduction (p = <0.0001) in mean of the bacteria colonies was observed with the increase of laser fluency doses at the same pulse duration. As well as, a significant reduction (p = <0.0001) in mean of the bacteria colonies was observed with in comparison between two laser fluencies at the same pulse duration. However, there are no significant differences in mean values of colony count between control and 5 J.cm⁻² at 20ms pulse duration. At 5ms and 10ms pulse durations, there are highly significant reduction (p < 0.0001) in mean of the colonies was observed with the increase of laser fluency doses at the same pulse duration. As well as, a highly significant reduction (P < 0.0001) in mean of the bacteria colonies was observed with in comparison between two laser fluencies at the same exposure time. However, at 20ms, there is no significant differences (P > 0.05) were noticed in mean of the bacteria colonies between the exposure times at 30 sec and 60 sec with all of the laser fluencies were used in current study. As well as, there are no significant differences (P > 0.05) in mean of the colonies between exposure times at 60 sec and 90 sec when laser fluency was at 15 J.cm⁻² , whereas there is significant difference (p = <0.05) when laser fluencies were at 5, 10 and 20 J.cm⁻². A significant difference was (p < 0.05) noticed in mean of the bacteria colonies between exposure times (30 sec and 90 sec) at all of the laser fluencies were used in our study except at 15 J.cm⁻² laser fluency>
In conclusion the exposure times, pulse durations and laser fluencies of pulsed alexandrite laser shown effect on the mean of bacterial count of S. aureus bacteria and determine effective dose.

Еlеctromagnetic Radiation (ЕMR)
Laser Historical Overview
Laser
Principles of Laser
Basic Elements of Laser
Types of laser
Long-Pulse Alexandrite (755 nm)
Spontaneous Emission
Thе production of lasеr radiation
Charactеristics of lasеr bеam
Action of Laser Light with tissue
Absorption
Scattering
Transmission
Wavelength Dependent Interaction Mechanisms
Photochemical interaction
Photo thermal interaction
Medical applications
Lasеr safеty
General description of Staphylococcus spp
Classification of Staphylococeus aureus
Pathogenicity of Staphylococcus aureus
Antibiotic resistance
The Aim of the study
The biological part: Materials and Methods
Apparatus and Instruments
Chemicals and biological materials
Media Preparation
Mannitol-Salt agar medium
Reagents, stains and solutions
Collection of isolates
Identification and Antibiotic susceptibility test of Staphylococcaceae using VITEK® 2 System
Preservation technique of bacterial isolates
Experimental Setups
Statistical analysis
Isolation and Identifction of Bacteria
Effect of Puls Alexandrite Laser according to expouser time

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