Fractional inhibitory concentration of bio-actives from agricultural waste disassembles biofilms and quenches virulence of nosocomial pathogens

<b>Introduction.</b> The contact surfaces in hospitals serve as reservoirs for pathogens and account for 20-40% of hospital-acquired infections. This resistance is mainly attributed to the biofilm-forming ability of the microbes. These biofilms restrict the entry of the antibiotics to penetrate them, thus giving rise to drug resistance. Hence, there is a renewed interest in formulating an environmentally friendly, non-allergic, quick mode of action, broad-spectrum disinfectant.<b>Hypothesis.</b> We hypothesize that the pure compounds present in the pyrolysis aqueous phase could act as an anti-infective and anti-biofilm agent.<b>Aim.</b> The present work investigates the effectiveness of furfuryl alcohol, 2-methyl-2-cyclopentenone and guaiacol as effective anti-infective agent followed by testing its biofilm eradication potential against the mixed species of multidrug-resistant pathogens such as <i>Acinetobacter baumannii</i>, methicillin-resistant <i>Staphylococcus aureus</i> and <i>Candida auris</i>.<b>Methodology.</b> The MIC and fractional inhibitory concentrations (FIC) of the pure compounds were determined using checkerboard assay for two-compound and three-compound combinations. The biofilm eradication concentration was performed on stainless coupons, followed by RNA isolation and quantitative PCR (qPCR) analysis to elucidate virulence gene downregulation.<b>Results.</b> The individual MICs of furfuryl alcohol, 2-methyl-2-cyclopentenone and guaiacol were found to be 8%, 9% and 2% (v/v), respectively. The two-compound combination FIC index of 0.75 showed partial synergy between the compounds, while the three-compound combination showed an additive effect with a FIC index of 0.87. Further, at ½ FIC (biofilm inhibitory concentration), the compounds showed 52% eradication of preformed biofilms on the hospital contact surfaces (stainless steel). The growth and time-to-kill curve showed that the compounds were not lethal to planktonic cells at BIC. Finally, the qPCR analysis showed a reduction in the expression levels of biofilm and adhesion genes, while the Quorum sensing (QS) genes were affected much more, elucidating a possible eradication mechanism.<b>Conclusion.</b> From this study, we have found a new class of compounds that have potential disinfecting ability. With the current knowledge, the future lead would be to effectively use them in disinfectant formulations.