Evidence of resistance development by Staphylococcus aureus to an in vitro, multiple stage application of 405 nm light from a supraluminous diode array.

OBJECTIVE

The aim of this study was to determine whether Staphylococcus aureus could develop a resistance to 405 nm light.

BACKGROUND DATA

Research indicates that certain wavelengths and treatment parameters of light promote growth of bacteria; however, our earlier work indicated that blue light effectively inactivates growth of S. aureus in vitro.

METHODS

S. aureus was tested because of its frequent isolation from skin infections and wounds. The organism was treated with 405 nm light from supraluminous diodes at a dose of 9 J/cm(2).

RESULTS

As anticipated, blue light produced a significant (p≤0.05) inactivation of S. aureus growth. Subsequent applications of blue light to subcultured generations of S. aureus were increasingly effective through four stages (generations). Beginning with stage five, a decrease in effectiveness (resistance) was observed.

CONCLUSIONS

Appropriate doses of 405-nm blue light inhibit the growth of S. aureus in vitro. This research does suggest that S. aureus may be capable of developing resistance to blue light irradiation.