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Streptococcus pneumoniae Eradicates Preformed Staphylococcus aureus Biofilms through a Mechanism Requiring Physical
Faidad Khan1, Xueqing Wu2, Gideon L Matzkin2
1Hubert Department of Global Health at the Rollins School of Public Health, Emory UniversityAtlanta, GA, USA; National Centre of Excellence in Molecular Biology, University of the PunjabLahore, Pakistan.
Abstract:
Staphylococcus aureus (Sau) strains are a main cause of disease, including nosocomial infections which have been linked to the production of biofilms and the propagation of antibiotic resistance strains such as methicillin-resistant Staphylococcus aureus (MRSA). A previous study found that Streptococcus pneumoniae (Spn) strains kill planktonic cultures of Sau strains. In this work, we have further evaluated in detail the eradication of Sau biofilms and investigated ultrastructural interactions of the biofilmicidal effect. Spn strain D39, which produces the competence stimulating peptide 1 (CSP1), reduced Sau biofilms within 8 h of inoculation, while TIGR4, producing CSP2, eradicated Sau biofilms and planktonic cells within 4 h. Differences were not attributed to pherotypes as other Spn strains producing different pheromones eradicated Sau within 4 h. Experiments using Transwell devices, which physically separated both species growing in the same well, demonstrated that direct contact between Spn and Sau was required to efficiently eradicate Sau biofilms and biofilm-released planktonic cells. Physical contact-mediated killing of Sau was not related to production of hydrogen peroxide as an isogenic TIGR4ΔspxB mutant eradicated Sau bacteria within 4 h. Confocal micrographs confirmed eradication of Sau biofilms by TIGR4 and allowed us to visualize ultrastructural point of contacts between Sau and Spn. A time-course study further demonstrated spatial colocalization of Spn chains and Sau tetrads as early as 30 min post-inoculation (Pearson's coefficient >0.72). Finally, precolonized biofilms produced by Sau strain Newman, or MRSA strain USA300, were eradicated by mid-log phase cultures of washed TIGR4 bacteria within 2 h post-inoculation. In conclusion, Spn strains rapidly eradicate pre-colonized Sau aureus biofilms, including those formed by MRSA strains, by a mechanism(s) requiring bacterium-bacterium contact, but independent from the production of hydrogen peroxide.
Insights
Streptococcus pneumoniae (Spn) rapidly eradicates Staphylococcus aureus (Sau) biofilms, including MRSA, through direct cell-to-cell contact. This mechanism is contact-dependent and does not involve hydrogen peroxide, offering a novel approach to combat persistent infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Interactions
Background:
- Staphylococcus aureus (Sau) causes significant disease, including hospital-acquired infections, due to biofilm formation and antibiotic resistance (e.g., MRSA).
- Previous research indicated Streptococcus pneumoniae (Spn) can kill planktonic Sau.
- The precise mechanism and efficacy of Spn against Sau biofilms remain underexplored.
Purpose of the Study:
- To investigate the detailed eradication of Sau biofilms by Spn.
- To elucidate the ultrastructural basis of Spn's biofilmicidal effect on Sau.
- To determine if Spn eradicates biofilms formed by antibiotic-resistant strains like MRSA.
Main Methods:
- Co-culture experiments with different Spn strains (D39, TIGR4) and Sau strains.
- Transwell assays to assess the necessity of direct contact.
- Confocal microscopy to visualize bacterial interactions and biofilm structure.
- Use of isogenic mutants (TIGR4ΔspxB) to investigate specific mechanisms (e.g., hydrogen peroxide production).
Main Results:
- Spn strain TIGR4 eradicated Sau biofilms and planktonic cells within 4 hours; strain D39 reduced biofilms within 8 hours.
- Direct physical contact between Spn and Sau was essential for efficient biofilm eradication.
- Eradication was independent of hydrogen peroxide production.
- Confocal microscopy confirmed biofilm eradication and revealed close spatial colocalization of Spn and Sau within 30 minutes.
- Pre-formed biofilms of Sau and MRSA were eradicated by Spn within 2 hours.
Conclusions:
- Streptococcus pneumoniae rapidly eradicates Staphylococcus aureus biofilms, including MRSA.
- The mechanism relies on direct bacterium-bacterium contact.
- This contact-dependent killing is independent of hydrogen peroxide production, suggesting a novel therapeutic avenue.
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