The effect of disinfectant formulation and organic soil on the efficacy of oxidising disinfectants against biofilms

BACKGROUND: Biofilms that develop on dry surfaces in the healthcare environment have increased tolerance to disinfectants. We compared the activity of formulated oxidizing disinfectants versus products containing only active ingredients against Staphylococcus aureus dry surface biofilm (DSB).
METHODS: DSB was grown in the CDC bioreactor with alternating cycles of hydration and dehydration. Disinfectant efficacy was tested before and after treatment with neutral detergent for 30 seconds and in the presence or absence of standardized soil. Biofilms were treated for 5 minutes with peracetic acid (Surfex and Proxitane), hydrogen peroxide (Oxivir and 6% H2O2 solution) and chlorine (Chlorclean and sodium dichloroisocyanurate [SDIC] tablets). Residual biofilm viability and mass were determined by plate culture and protein assay respectively.
FINDINGS: Biofilm viability was reduced by 2.8 Log10 for the chlorine-based products and by 2 Log10 for Proxitane but these products failed to kill any biofilm in the presence of the soil. In contrast, the formulated Surfex completely inactivated biofilm (6.3log10 reduction in titre) in the presence of soil. H2O2 products had little effect against DSB. Biofilm mass removed in the presence and absence of soil was <30% by chlorine and approximately 65% by Surfex. Detergent treatment prior to disinfection had no effect.
CONCLUSION: The additives in fully formulated disinfectants can act synergistically with active ingredients and thus increase biofilm killing whilst decreasing the adverse effect of soil. We suggest that purchasing officers seek efficacy testing results and consider whether efficacy testing has been conducted in the presence of biological soil and/or biofilm.
REFERENCE:
Chowdhury D, et al. The effect of disinfectant formulation and organic soil on the efficacy of oxidising disinfectants against biofilms. J Hosp Infect. 2018 Oct 26. pii: S0195-6701(18)30556-5. doi: 10.1016/j.jhin.2018.10.019.
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