Abstract
BackgroundPolymicrobial infections are responsible for significant mortality and morbidity in adults and children. Staphylococcus epidermidis and Candida albicans are the most frequent combination of organisms isolated from polymicrobial infections. Vascular indwelling catheters are sites for mixed species biofilm formation and pose a significant risk for polymicrobial infections. We hypothesized that enhancement of biofilms in a mixed species environment increases patient mortality and morbidity.ResultsMixed species biofilms of S. epidermidis and C. albicans were evaluated in vitro and in a subcutaneous catheter infection model in vivo. Mixed species biofilms were enhanced compared to single species biofilms of either S. epidermidis or C. albicans. A mixed species environment increased catheter infection and increased dissemination of S. epidermidis in mice. Microarrays were used to explore differential gene expression of S. epidermidis in the mixed species biofilms. In mixed species biofilms, compared to single species S. epidermidis biofilms, 2.7% of S. epidermidis genes were upregulated and 6% were down regulated. Staphylococcal autolysis repressors lrgA and lrgB were down regulated 36-fold and 27-fold respectively. The role of biofilm extracellular DNA was investigated by quantitation and by evaluating the effects of DNAse in a concentration and time dependent manner. S. epidermidis specific eDNA was increased in mixed species biofilms and further confirmed by degradation with DNAse.ConclusionsMixed-species biofilms are enhanced and associated with increased S. epidermidis-specific eDNA in vitro and greater systemic dissemination of S. epidermidis in vivo. Down regulation of the lrg operon, a repressor of autolysis, associated with increased eDNA suggests a possible role for bacterial autolysis in mixed species biofilms. Enhancement and systemic dissemination of S. epidermidis may explain adverse outcomes after clinical polymicrobial infections of S. epidermidis and C. albicans.
Highlights
Polymicrobial infections are responsible for significant mortality and morbidity in adults and children
Mixed species biofilms are larger than single species biofilms of S. epidermidis and C. albicans Representative confocal images of S. epidermidis, C. albicans and mixed species biofilms grown in microwell petridishes for 24 hr, stained with LIVE/ DEAD, at 40× magnification, in the green, red and merged channels are presented in Figures 1A, 1B and 1C respectively
Biofilms are enhanced in a mixed-species environment of S. epidermidis and C. albicans both in vitro and in vivo
Summary
Polymicrobial infections are responsible for significant mortality and morbidity in adults and children. Vascular indwelling catheters are sites for mixed species biofilm formation and pose a significant risk for polymicrobial infections. We hypothesized that enhancement of biofilms in a mixed species environment increases patient mortality and morbidity. In vitro interactions of Candida albicans and S. epidermidis in mixed species biofilms and decreased antimicrobial susceptibility have been reported [16,17]. Interactions of S. epidermidis with Candida in mixed species infections may influence gene expression that may lead to enhanced virulence, biofilm formation, biofilm dispersal and tissue pathology have not been well studied. A significant risk factor for human polymicrobial infections is the presence of indwelling vascular catheters that are sites for mixed species biofilm formation [2]. Significant mixed species biofilms of the pathogens S. epidermidis and Candida and the specific role of eDNA in mixed species biofilms have not been investigated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
