Antibacterial Effect of Low-Level Laser (Diode 405 nm) on Antibiotic-Resistant Enterococci Clinical Isolates (In Vitro)

Enterococcus is a part of normal gastrointestinal flora in human body. Nevertheless, antibiotic-resistant Enterococcus (ARE) is considered a key factor in nosocomial infections which result in a considerable increase in the rate of patient death due to referring of numerous patients to health centers annually, or lead to extended disease convalescence.

This study aimed to evaluate the bactericidal effect at 405nm diode at a laser power of 30 mW on ARE viability of clinical infections.

In the present study, 30 isolates underwent antibiotic susceptibility test (AST) in which sensitivity to piperacillin (100 µg), rifampin (5 µg), and oxacillin (1 µg) were measured based on the Clinical and Laboratory Standards Institute (CLSI) guidelines. Afterwards, ten most resistant isolates were selected and irradiated by a 405 nm diode laser at a power of 30 mW for 180 and 240 seconds. The data were reported statistically as mean ± standard deviation, and the analysis of the data on varied bacteria was performed using ANOVA. The result was evaluated by SPSS software and P value ≤0.05 was interpreted to be significant.

Bacterial viability decreased unsteadily to 10 resistant isolates. Moreover, enhancing irradiation time caused a lower viability rate in such a way that the viability of isolate 9 having the lowest viability rate was reduced from 2.94% in 180 seconds to 0.58% in 240 seconds. The result was evaluated by SPSS software and P value was determined to be significant, and P≤0.05 was laser irradiation for either 180 s or 240 s.

Following the study results, 405 nm diode laser could be applied as a tool for eliminating clinical ARE, and it was useful for preventing hospital-acquired infections.