Impact of mixed Staphylococcus aureus-Pseudomonas aeruginosa biofilm on susceptibility to antimicrobial treatments in a 3D in vitro model

• Published in: Scientific reports Vol. 14; no. 1; pp. 27877 - 14
• Main Authors: Landa, Guillermo, Clarhaut, Jonathan, Buyck, Julien, Mendoza, Gracia, Arruebo, Manuel, Tewes, Frederic
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13-11-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 631/326; 631/80; Antimicrobial activity; Antimicrobial agents; Antiseptics; Bacteria; Biofilms; Chlorhexidine; Coexistence; Humanities and Social Sciences; Microenvironments; Monoculture; multidisciplinary; Polymicrobial biofilm; Pseudomonas aeruginosa; Science; Science (multidisciplinary); Staphylococcus aureus; Thymol; Chlorhexidine; Polymicrobial biofilm; Thymol; Antiseptics
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-024-79573-y

Staphylococcus aureus
and
Pseudomonas aeruginosa
are the most common bacteria co-isolated from chronic infected wounds. Their interactions remain unclear but this coexistence is beneficial for both bacteria and may lead to resistance to antimicrobial treatments. Besides, developing an in vitro model where this coexistence is recreated remains challenging, making difficult their study. The aim of this work was to develop a reliable polymicrobial in vitro model of both species to further understand their interrelationships and the effects of different antimicrobials in coculture. In this work, bioluminescent and fluorescent bacteria were used to evaluate the activity of two antiseptics (chlorhexidine and thymol) against these bacteria planktonically grown, or when forming single and mixed biofilms. At the doses tested (0.4-1,000 mg/L), thymol showed selective antimicrobial action against
S. aureus
in planktonic and biofilm states, in contrast with chlorhexidine which exerted antimicrobial effects against both bacteria. Furthermore, the initial conditions for both bacteria in the co-culture determined the antimicrobial outcome, showing that
P. aeruginosa
impaired the proliferation and metabolism of
S. aureus
. Moreover,
S. aureus
showed an increased tolerance against antiseptic treatments when co-cultured, attributed to the formation of a thicker mixed biofilm compared to those obtained when monocultured, and also, by the reduction of
S. aureus
metabolic activity induced by diffusible molecules produced by
P. aeruginosa.
This work underlines the relevance of polymicrobial populations and their crosstalk and microenvironment in the search of disruptive and effective treatments for polymicrobial biofilms.