In vitro evaluation of multiple antibacterial agents for the treatment of chronic staphylococcal anterior blepharitis

To evaluate the bactericidal efficacy of several compounds used in the treatment of chronic staphylococcal anterior blepharitis through an in vitro study.

Standard commercial strains of Staphylococcus aureus (SAu) (ATCC 25923 Culti-Loops) and coagulase-negative Staphylococcus (CoNS) (ATCC 12228 Culti-Loops) were cultured. Susceptibility tests were performed to vancomycin 30 μg, netilmicin 30 μg, hypochlorous acid (HOCl) 0.01% (Ocudox™, Brill®), Melaleuca alternifolia leaf oil (MeAl) (Navyblef® Daily Care, NOVAX®) and 1% chlorhexidine digluconate (DGCH) (Cristalmina™, Salvat®) using the agar disk diffusion method (Rosco Neo-Sensitabs®). After 24 h, the induced halos were measured with automatic calipers. The results were analyzed using the EUCAST- and CLSI potency Neo-Sensitabs® guidelines.

Vancomycin induced a halo of 22.37 mm and 21.81 mm in SAu and CoNS, respectively. Netilmicin produced halos of 24.45 mm in SAu and 32.49 mm in CoNS. MeAl induced halos of 12.65 mm in SAu and 15.83 mm in CoNS. A 12.11 mm halo was found in SAu and an 18.38 mm halo in CoNS using HOCl. DGCH produced halos of 26.55 mm and 23.12 mm in SAu and CoNS, respectively.

Netilmicin and vancomycin demonstrated antibiotic activity against both pathogens, so they can be alternative rescue therapies to treat chronic staphylococcal blepharitis. DGCH has efficacy against both comparable to antibiotics, while HOCl and MeAl show less efficacy.