Aug. 28, 2026
Can a 450 nm LED kill streptococcus? And what is its effective kill rate against streptococci?
The bactericidal effect of 450 nm LED light on streptococci varies from species to species — there is no single, uniform answer.
Current research shows that 450 nm blue light is effective against some streptococci but has very little effect on others. The specific kill rates are as follows:
Streptococcus salivarius: a kill rate of about 52%. The study used specific parameters (an intensity of 10 mW/cm² and a total dose of 75.6 J/cm²).
Streptococcus agalactiae (Group B streptococcus): essentially no effect. Even though this bacterium contains pigments that can absorb blue light, 450 nm light cannot kill it effectively.
Streptococcus mutans: research shows that 450 nm blue light on its own has a limited effect; it generally needs to be combined with a photosensitizer (such as curcumin) in antimicrobial photodynamic therapy (aPDT) to enhance the bactericidal effect.
