S. aureus modulates P. aeruginosa small-colony variants formation

Abstract

Some studies reported that, in polymicrobial consortia, some P. a eruginosa exoproducts suppresses the growth of S.aureus and provokes the emergence of SCV, associated with antimicrobial resistance, altered metabolism and reduced immunogenicity. However, the role of S.aureus in P.aerugionsa behavior has still not been deciphered. This work aimed to deeply investigate the phenotypic changes undergone by P. aeruginosa and S.aureus in a co-infection scenario. The cells recovered from 24 -h-old single and dual-species biofilms were inspected regarding their colony morphology differentiation, antibiotic susceptibility profiles and expression of virulence factors. The population analysis profiles showed the existence of two P.aeruginosa SCV resulting only from the dual-species biofilms. These SCV exhibited impressive ability to form biofilm, impaired swimming, twitching and swarming abilities, in comparison with the wild -type morphotype. Their morphologies remained unchangeable over 10 passages onto solid media, which may mean these phenotypic alterations were not adaptive. Yet, the two SCV were susceptible to the action of several classes of antibiotics. In conclusion, the presence of S.aureus in biofilms seemed to modulate some phenotypic alterations in P.aeruginosa that may be clinically relevant as two SCV were detected. As t he role of S. aureus over P. aeruginosa stills not full clear, some tests are being run to more comprehensively know how these P. aeruginosa SCV modulate the dual -species community response to in - use antimicrobials.