Activity of Colloidal Silver Solution against Microorganisms Implicated in Ocular Infections

Abstract: Endophthalmitis most likely originates from both planktonic bacteria suspended in the tear film and bacteria adherent to the conjunctiva and the eyelid. This study aimed to expand the research on the effectiveness of a colloidal silver solution (Silverix®) against ocular microorganisms. The activity of Silverix® was evaluated against methicillin-resistant Staphylococcus aureus, S. epidermidis, ofloxacin-resistant Pseudomonas aeruginosa, and Candida albicans strains, previously characterized for their antibiotic resistance and biofilm-forming capabilities. The microbial killing was estimated at various times in the presence and absence of colloidal silver solution against planktonic and biofilmembedded cells. The results documented the efficacy of Silverix® on planktonic cells of S. aureus and S. epidermidis (2.49–2.87 Log CFU/mL reduction) and P. aeruginosa strains (3–4.35 Log CFU/mL reduction). On the contrary, C. albicans showed mild susceptibility. Regarding early biofilm, the ocular isolates were harder to kill (2–2.6 Log CFU/mL reduction) than the reference strains, whereas a similar decrease (3.1 Log CFU/mL reduction) was estimated for P. aeruginosa strains. The light microscope images of biofilms treated with colloidal solution confirmed the ability of Silverix® to destroy the biofilm.