Microbial interactions and differential protein expression inStaphylococcus aureus–Candida albicansdual-species biofilms

Abstract

The fungal species Candida albicans and the bacterial species Staphylococcus aureus are responsible for a majority of hospital-acquired infections and often coinfect critically ill patients as complicating polymicrobial biofilms. To investigate biofilm structure during polymicrobial growth, dual-species biofilms were imaged with confocal scanning laser microscopy. Analyses revealed a unique biofilm architecture where S. aureus commonly associated with the hyphal elements of C. albicans. This physical interaction may provide staphylococci with an invasion strategy because candidal hyphae can penetrate through epithelial layers. To further understand the molecular mechanisms possibly responsible for previously demonstrated amplified virulence during coinfection, protein expression studies were undertaken. Differential in-gel electrophoresis identified a total of 27 proteins to be significantly differentially produced by these organisms during coculture biofilm growth. Among the upregulated staphylococcal proteins was l-lactate dehydrogenase 1, which confers resistance to host-derived oxidative stressors. Among the downregulated proteins was the global transcriptional repressor of virulence factors, CodY. These findings demonstrate that the hyphae-mediated enhanced pathogenesis of S. aureus may not only be due to physical interactions but can also be attributed to the differential regulation of specific virulence factors induced during polymicrobial growth. Further characterization of the intricate interaction between these pathogens at the molecular level is warranted, as it may aid in the design of novel therapeutic strategies aimed at combating fungal–bacterial polymicrobial infection.

Mixed biofilms formed by C. albicans and non-albicans species: a study of microbial interactions

“…16 Some microorganisms have evolved mutualistic or even synergistic interactions to facilitate cohabitation on epithelial surfaces and to utilize metabolic by-products efficiently, whereas others have developed competitive antagonistic approaches during colonization. 23 Species of the genus Candida are the most prevalent fungal pathogens in the oral cavity, and their ability to form biofilms is associated with their virulence.…”

“…15 Polymicrobial biofilms are found in nearly every niche in the human body. 16 These mixtures of species make the therapeutic management of infectious diseases extremely difficult. 12 The heterogeneity of species within mixed biofilms has made it difficult to assess the relevance and contribution of each individual species to pathogenesis and disease.…”

Pathogenesis of Polymicrobial Biofilms

“…A recent study examining the structure of biofilm formed by C. albicans and the bacterial pathogen Staphylococcus aureus as they coexist revealed a unique architecture where S. aureus associated with the hyphae of C. albicans. Further characterization of this seemingly synergistic type of interaction at the molecular level demonstrated significant level of differential protein expression the result of the mixed-species biofilm mode of growth [29]. Interestingly, a number of these proteins were identified to be virulence factors in S. aureus indicating a process whereby C. albicans may enhance S. aureus pathogenesis [29].…”

“…Further characterization of this seemingly synergistic type of interaction at the molecular level demonstrated significant level of differential protein expression the result of the mixed-species biofilm mode of growth [29]. Interestingly, a number of these proteins were identified to be virulence factors in S. aureus indicating a process whereby C. albicans may enhance S. aureus pathogenesis [29]. These findings are of great significance as these two species are currently ranked as the second and third most commonly isolated bloodstream pathogens in hospitalized patients [24].…”

Evaluation of a Rapid Oral Bacteria Quantification System Using Dielectrophoresis and the Impedance Measurement

“…Staphylococci and Candida species are drawing new attention because these microorganisms affect the emergence and establishment of antimicrobial resistance because of the high involvement of biofilms in chronic and systemic infections Peters et al, 2010 . P. aeruginosa and S. aureus are opportunistic pathogens and frequently co-infect the lungs of cystic fibrosis patients Folescu et al, 2012 .…”