# Biocompatible Guanidine-Functionalized Compounds with Biofilm and Membrane Disruptive Activity Against MRSA

## TL;DR

This paper introduces new guanidine-based compounds that effectively combat MRSA by disrupting biofilms and bacterial membranes without causing toxicity.

## Contribution

The study presents novel guanidine-functionalized compounds with dual mechanisms against MRSA biofilms and membranes.

## Key findings

- The compounds showed bacteriostatic effects with MICs of 2.34–4.68 μg/mL against MRSA.
- They reduced biofilm biomass and metabolic activity, confirmed by SEM and fluorescence microscopy.
- The compounds exhibited synergistic effects with oxacillin and low resistance induction potential.

## Abstract

Three guanidine-functionalized 3,4-dihydropyrimidin-2­(1H)-imine compounds (5a, 5b, 5c) were synthesized from 3,5-diaryldiene-4-piperidone and
evaluated for antibacterial and antibiofilm activity against Staphylococcus aureus, CA-MRSA and HA-MRSA. The compounds
showed bacteriostatic effects (MICs: 2.34–4.68 μg/mL).
In vitro antibiofilm potential was demonstrated by significant reductions
in biomass and metabolic activity, and structural analyses via SEM
and fluorescence microscopy. Ex vivo antibiofilm activity was confirmed
in porcine skin model. RT-qPCR revealed downregulation of biofilm
associated virulence genes, indicating a multifactorial mechanism.
Confocal microscopy showed increased levels of extracellular DNA and
proteins, suggesting disruption of the biofilm matrix. Membrane interaction
assays demonstrated time- and dose-dependent effects, suggesting a
complementary mechanism of action. Compounds 5a and 5c exhibited synergistic and additive effects with oxacillin.
The compounds were stable intracellularly, and resistance studies
revealed low induction potential. Biocompatibility was confirmed by
lack of mutagenicity, hemolysis, or cytotoxicity. Moreover, in vivo
efficacy was demonstrated by survival of Tenebrio molitor larvae infected with S. aureus and
treated. These guanidine-based compounds are promising candidates
for new MRSA drug development.