In vitro determination of the antibiotic susceptibility of biofilm-forming Pseudomonas aeruginosa and Staphylococcus aureus: possible role of proteolytic activity and membrane lipopolysaccharide

Abstract

We carried out a comprehensive overview of inhibitory effects of selected antibiotics on planktonic and biofilm cells of Staphylococcus aureus (ATCC 29213) and Pseudomonas aeruginosa (ATCC 27853) strains. The possible involvement of protease activity and the lipopolysaccharide (LPS) profile of P. aeruginosa were also analyzed. Biofilm cells of both strains were more resistant to antibiotics than their planktonic counterparts. Protease activity was increased in both strains in the biofilm forms. Challenge with sublethal doses of antibiotics also increased proteolytic activity of biofilm cells. Additionally, the LPS profile of P. aeruginosa showed pattern alterations of the biofilm that can contribute to biofilm resistance and survival. These observations provide evidence for the involvement of bacterial proteolytic activity and LPS profile in the resistance of biofilm bacteria to antibiotics compared to their planktonic counterparts.

Keywords:

• biofilm
• Pseudomonas aeruginosa
• Staphylococcus aureus
• proteolytic activity
• lipopolysaccharide

Supplementary tables

Table S1 Minimum inhibitory concentration values of Staphylococcus aureus planktonic and biofilm cells

Table S2 Minimum inhibitory concentration values of Pseudomonas aeruginosa planktonic and biofilm cells

Acknowledgment

This project was supported by a grant (No 37/2010) from the Deanship of Research at the Jordan University of Science and Technology.

Disclosure

The authors report no conflicts of interest in this work.