Antimicrobial Blue Light: An Alternative Therapeutic for Multidrug-Resistant Gonococcal Infections?

Gonorrhea is the second most prevalent sexually transmitted infection globally. Neisseria gonorrhoeae, the etiological agent of gonorrhea, is evolving into a superbug and may become untreatable due to its resistance to almost all the antibiotics available. There is a critical need for the development of alternative therapeutics. This pilot study aimed to investigate the potential of an innovative non-antibiotic approach, antimicrobial blue light (aBL), as an alternative therapeutic for gonococcal infections. We studied one ATCC strain (ATCC 700825) and one multidrug-resistant clinical strain of N. gonorrhoeae. The results demonstrated that both the strains are highly susceptible to aBL at 405nm. In planktonic suspensions, an exposure of 45 J/cm2 aBL reduced the survival fraction of colony-forming units (CFU) by 7.16-log10 for ATCC 700825 and 2.48-log10 for the clinical strain. When the aBL exposure was further increased to 54 J/cm2, a complete eradication of CFU (over 8-log10 CFU reduction) was achieved for ATCC 700825 and a reduction of 5.43-log10 CFU was obtained for the clinical strain. In addition, we observed that singlet oxygen plays a vital role in the antimicrobial effect of aBL on N. gonorrhoeae. In conclusion, the results of this pilot study suggest that aBL is a promising approach to combat gonococcal infections. Further studies are warranted in the analysis of the endogenous photosensitizers in N. gonorrhoeae cells, evaluation of the aBL efficacy against gonococcal infections in animal models, and investigation of the mechanism of action of aBL.