Efficacy of antiseptics containing povidone-iodine, octenidine dihydrochloride and ethacridine lactate against biofilm formed by Pseudomonas aeruginosa and Staphylococcus aureus measured with the novel biofilm-oriented antiseptics test

Abstract

Increasing data suggesting that microorganisms in the biofilm form are among the leading agents of persistent infections of chronic wounds require the development of new approaches to treatment. The aim of this article was to compare the efficacy of three commonly used antiseptics using a biofilm-oriented approach. Biofilm-oriented antiseptics test (BOAT), the innovative method, allows to estimate, in a quick and reliable manner, the in vitro activity of working solutions of antiseptics in real contact times against bacteria in the biofilm form and to use the results in the selection of an appropriate antiseptic to treat local infections in the clinical practice.

Keywords: Antiseptics; Biofilm-oriented approach; P. aeruginosa; S. aureus.

Figure 1

Staphylococcal and pseudomonal biofilm formed on the polystyrene disc. Scanning electron microscopy micrographs of Pseudomonas aeruginosa 15445 (A) and Staphylococcus aureus ATTC 5638 (B) biofilms formed on the surface of polystyrene discs. The adhered cocci and pseudomonal cells, as well as the extracellular layers visualised at the micrograph, confirm the ability of the investigated strains to form biofilm on the polystyrene within 24 hours. Scanning electron microscope ZEISS EVO MA 25.

Figure 2

Sample biofilm‐oriented antiseptics test (BOAT). The bottoms of the indicated wells of the microtitre polystyrene assay plate are coated with bacterial biofilm. The dark red colour of the wells means that the bacteria in the biofilm form survived the treatment with the antiseptic within the contact time, whereas the lack of red colour is equivalent to a complete eradication of the bacteria forming biofilm in the well. Line 1 – positive control (biofilm untreated with antiseptic), confirming the ability of the tested strain 2034 to form biofilm at the bottom of the well; line 2 – negative control wells filled with the medium (no biofilm) confirming sterility of the assay performed; line 3: wells A, B, C – strain 2034 treated with octenidine for 1 minute; wells D, E, F – the same strain treated with PVP‐iodine; wells G, H, I – strain treated with ethacridine. Analogically, the biofilm from wells in lanes 4 and 5 was treated with the above‐mentioned antiseptics for 15 and 30 minutes, respectively.