Novel antimicrobial efficacy on inert surfaces of chlorhexidine-silver nanoparticle veterinary formulation

Aim: This study aimed to establish the in vitro efficacy of chlorhexidine (CHX)-silver nanoparticles (AgNP) based preparation, against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) in planktonic cultures, biofilms, and on inert stainless-steel surfaces. Methods: The in vitro antimicrobial activity of the CHX-AgNP formulation (Dermosedan MRSA Nano AG®) was evaluated against reference and multidrug-resistant (MDR) strains of S. aureus and P. aeruginosa by determining the minimum inhibitory and bactericidal concentrations (MIC and MBC), as well as the minimum biofilm inhibitory and eradication concentrations (MBIC and MBEC). Also, the residual bactericidal activity on inert stainless-steel surfaces was evaluated. Results: MIC against methicillin-resistant S. aureus (MRSA) and MDR P. aeruginosa (MDR-PA) isolates ranged between 5/2.5–20/10 µg/mL, up to 8,000 times lower than the manufacturer’s recommended concentration, while MBC ranged from 500 to 2,000 times lower. MBIC matched the MBC, while higher concentrations were needed to eradicate preformed biofilms. On stainless-steel surfaces, high antimicrobial activity was observed for both pathogens. No bacterial survival was detected even after 6 hours at 4% CHX + 2% AgNP concentration. The CHX-AgNP combination demonstrated strong antimicrobial and antibiofilm activity against both S. aureus and P. aeruginosa. Conclusions: These results support the potential application of Dermosedan MRSA Nano AG® as a strategy for managing topical resistant infections and for environmental disinfection in both veterinary and clinical settings.