Introduction:

Skin ulcers are frequently colonized with pathogens, including multi-drug resistant bacteria (MDRB). This leads to chronic, non-healing wounds. The formation of biofilms protects bacteria against antibiotics and many disinfectants. A promising treatment option is pharmaceutical NaClO2 (sodium chlorosum). Sodium chlorosum generates reactive chlorine oxygen species (RClOS) and was previously shown to promote healing of diabetic, arterial, venous and Leishmania ulcers and to kill Leishmania pro- and amastigotes in vitro. Based on its clinical effects, we hypothesize that sodium chlorosum kills antibiotic-sensitive and -resistant bacteria and disrupts bacterial biofilms.

Methods:

We used Gram-positive and Gram-negative bacterial species including antibiotic-sensitive strains and MDRB. To analyze the bacteriostatic effect, bacteria ± sodium chlorosum were incubated for 6 h. Optical density was measured hourly as a marker for bacterial growth. Bactericidal effects were determined by incubating bacteria for 4 h with sodium chlorosum. The samples were plated on agar plates and the number of colony-forming units (CFU) was determined. Biofilms were grown by incubating bacterial samples for 24 h in a 96-well plate. Sodium chlorosum was added, and samples were incubated again for 24 h. Biofilm viability and mass were determined with a resazurin-based stain and crystal violet, respectively.

Results:

Concentrations <500µM of sodium chlorosum inhibited the growth of most of the bacteria tested (e.g. S. aureus, P. mirabilis, E. coli) except for few species (e.g., E. faecium). Concentrations above 1000µM exhibited bactericidal effects in most bacterial species tested. While methicillin-resistant S. aureus (MRSA) was susceptible to low concentrations of sodium chlorosum, vancomycin-resistant E. faecium (VRE) was resistant. Biofilm viability and mass decreased in the presence of higher concentrations of sodium chlorosum in all tested bacterial strains.

Conclusion:

Sodium chlorosum exhibits bactericidal and bacteriostatic effects and reduces biofilm viability and mass of various bacteria. Effects on MDRB are variable and depend on the bacterial species.