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Microbial species behave without antagonism, apparent synergism inside biofilms
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Within the microbial populations attached to a substrate and surrounded by a self-derived extracellular matrix known as biofilms, Candida albicans, methicillin-susceptible Staphylococcus aureus, and MRSA can coexist without antagonism, according to research published in the American Journal of Clinical Pathology.
Inside these environments, which are estimated to lead to more than half of hospital infections, the species may even behave synergistically with bacteria demonstrating preferences to C. albicans, according to researchers.
“Mono or polymicrobial infections are complex processes regulated by a dynamic equilibrium among the host immune defense, microorganisms’ interaction and their virulence factors,” the researchers wrote. “This study demonstrated that C. albicans, MSSA, and MRSA can co-exist in a biofilm mode of growth, in an apparent synergistic effect, with bacteria cells preferentially associated to hyphal forms.”
Chaiene Evelin Zago, a PhD student at São Paulo State University, Brazil, with Carlos Eduardo Vergani, PhD, and colleagues studied the interaction between C. albicans, methicillin-susceptible S. aureus (MSSA) and MRSA in single- and dual-species biofilms.
The investigators evaluated species adhesion over 90 minutes, as well as biofilms over 12, 24 and 48 hours using counting colony-forming units, XTT-reduction and crystal violet staining. Fluorimetric kits were used to assess secretion of hydrolytic enzymes among 48 hour biofilms, and scanning electron microscopy to assess biofilm structure.
The researchers compared results from quantification assays using two-way ANOVAs with Tukey post-hoc tests and analyzed data from enzymatic activities using one-way Welch-ANOVA with Games-Howell post hoc test.
In single and mixed cultures, C. albicans, MSSA and MRSA were able to adhere and form biofilm. All microorganisms in both growth conditions showed a steady increase over time in cell number and metabolic activity; peak values were observed between 12 and 48 hours (P < .05).
Total biomass values were significantly higher (P < .05) among C. albicans single- and dual-species biofilms vs. single biofilms of bacteria.
All microorganisms in both growth conditions secreted proteinase and phospholipase-C, except for single MRSA biofilms. Scanning electron microscopy revealed extensive adherence of bacteria to hyphal elements of C. albicans.
“This study contributed to the understanding of the complex interactions between microbial species, which would provide a new perspective for developing new strategies for the prevention, control and treatment of polymicrobial infections,” the researchers wrote. – by Allegra Tiver
Disclosure: The researchers report no relevant financial disclosures.
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