Low-power lasers on bacteria: stimulation, inhibition, or effectless?

Area of Science:

• Biomedical Engineering
• Photomedicine
• Microbiology

Background:

• Low-power laser therapy (LPLT) is utilized for various clinical applications, including pain relief and wound healing.
• Concerns exist regarding potential adverse effects of LPLT on infected tissues.
• Existing research shows conflicting results on LPLT's impact on bacterial cultures, with effects ranging from stimulation to inhibition or no effect.

Purpose of the Study:

• To review existing studies on the effects of low-power lasers on bacteria.
• To propose a hypothesis explaining the variable effects of LPLT on bacterial growth.

Main Methods:

• A comprehensive literature search was conducted to identify relevant published reports.
• Analysis of experimental data focusing on physical laser parameters and biological factors.

Main Results:

• Experimental data indicate that the effects of low-power lasers on bacteria are contingent upon specific physical laser and biological parameters.
• The outcome on bacterial cells may depend on the degree of stimulation of endogenous photoacceptors or excitation of endogenous photosensitizers.

Conclusions:

• The observed variability in LPLT's effects on bacteria can be attributed to a complex interplay of specific laser and biological factors.
• A balance or dominance between stimulation of photoacceptors and excitation of photosensitizers likely dictates the final impact on bacterial cells.