Resistance of Bacteria toward 475 nm Blue Light Exposure and the Possible Role of the SOS Response

The increase in antibiotic resistance represents a major global challenge for our health systems and calls for alternative treatment options, such as antimicrobial light-based therapies. Blue light has shown promising results regarding the inactivation of a variety of microorganisms; however, most often, antimicrobial blue light (aBL) therapy is performed using wavelengths close to the UV range. Here we investigated whether inactivation was possible using blue light with a wavelength of 475 nm. Both Gram-positive and -negative bacterial strains were treated with blue light with fluences of 7.5–45 J/cm2. Interestingly, only some bacterial strains were susceptible to 475 nm blue light, which was associated with the lack of RecA, i.e., a fully functional DNA repair mechanism. We demonstrated that the insertion of the gene recA reduced the susceptibility of otherwise responsive bacterial strains, indicating a protective mechanism conveyed by the bacterial SOS response. However, mitigating this pathway via three known RecA inhibiting molecules (ZnAc, curcumin, and Fe(III)-PcTs) did not result in an increase in bactericidal action. Nonetheless, creating synergistic effects by combining a multitarget therapy, such as aBL, with an RecA targeting treatment could be a promising strategy to overcome the dilemma of antibiotic resistance in the future

Prospective Study on the Influence of Occupational Hand Protection Products on the Efficacy of Hand Disinfection

Abstract: To prevent occupational skin diseases, employees are instructed to periodically apply hand protection products as a barrier to protect their hands from water, cleaning agents or other irritants. The aim of this work was to investigate whether bacteria present on the skin at the time of protection product application are enclosed underneath this protective layer, if they can be transferred to other surfaces and if a standard isopropanol-based skin disinfectant can nonetheless reduce the bacterial burden.This prospective study was conducted in human volunteers based on the European Standard (EN 1500) to assess the burden of microorganisms before and after the application of various protection product formulations and subsequent hand disinfection.All protection products, with the exception of alcohol-based gels, enclosed bacteria underneath a lipid layer which could be transferred onto other surfaces. Still, the hand disinfectant efficiently reduced the bacteria burden.In occupations where proper hand hygiene is vital, alcohol-based gels might be the best option for the protection of the skin barrier as well as for reducing the contamination risk.An alcohol-based disinfection agent can dissolve the lipid film of protection products following the standard protocol for hygienic hand disinfection