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Streptococcus pneumoniae Eradicates Preformed Staphylococcus aureus Biofilms through a Mechanism Requiring Physical Contact

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus

Spn TIGR4 eradicates Sau biofilms produced by strain Newman and MRSA USA300. Sau strain Newman (A,B) or USA300 (C,D) was inoculated alone or with Spn strain TIGR4 and plates were incubated for 4 h at 37°C. Planktonic cells or biofilms were harvested, serially diluted and plated onto salt mannitol agar plates to obtain Sau counts or blood agar plates with gentamicin to obtain TIGR4 counts. Error bars represent the standard errors of the means calculated using data from at least three independent experiments. The median (cfu/ml) is shown inside the bars. *statistical significance (p < 0.05) in comparison to wells inoculated only with Sau.
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Figure 2: Spn TIGR4 eradicates Sau biofilms produced by strain Newman and MRSA USA300. Sau strain Newman (A,B) or USA300 (C,D) was inoculated alone or with Spn strain TIGR4 and plates were incubated for 4 h at 37°C. Planktonic cells or biofilms were harvested, serially diluted and plated onto salt mannitol agar plates to obtain Sau counts or blood agar plates with gentamicin to obtain TIGR4 counts. Error bars represent the standard errors of the means calculated using data from at least three independent experiments. The median (cfu/ml) is shown inside the bars. *statistical significance (p < 0.05) in comparison to wells inoculated only with Sau.

Mentions: Experiments with another Spn reference strain TIGR4, and Sau strain Newman, were also conducted. Whereas, Sau planktonic cells and biofilms reached, 4 h post-inoculation, a bacterial density of ~4.6 × 107 cfu/ml and ~9.8 × 106 cfu/ml, respectively, Sau planktonic cells and biofilms were eradicated (<50 cfu/ml) when they were incubated with strain TIGR4 for 4 h (Figure 2A). TIGR4 planktonic cells, or biofilms, remained unchanged whether incubated alone or with Sau for 4 h (Figure 2B). MRSA strain USA300, Sau ATCC 25923, SAJV01, were also challenged with TIGR4 for 4 h and eradication of both planktonic and biofilms was similarly observed (Figures 2C,D and not shown).


Streptococcus pneumoniae Eradicates Preformed Staphylococcus aureus Biofilms through a Mechanism Requiring Physical Contact
Spn TIGR4 eradicates Sau biofilms produced by strain Newman and MRSA USA300. Sau strain Newman (A,B) or USA300 (C,D) was inoculated alone or with Spn strain TIGR4 and plates were incubated for 4 h at 37°C. Planktonic cells or biofilms were harvested, serially diluted and plated onto salt mannitol agar plates to obtain Sau counts or blood agar plates with gentamicin to obtain TIGR4 counts. Error bars represent the standard errors of the means calculated using data from at least three independent experiments. The median (cfu/ml) is shown inside the bars. *statistical significance (p < 0.05) in comparison to wells inoculated only with Sau.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037180&req=5

Figure 2: Spn TIGR4 eradicates Sau biofilms produced by strain Newman and MRSA USA300. Sau strain Newman (A,B) or USA300 (C,D) was inoculated alone or with Spn strain TIGR4 and plates were incubated for 4 h at 37°C. Planktonic cells or biofilms were harvested, serially diluted and plated onto salt mannitol agar plates to obtain Sau counts or blood agar plates with gentamicin to obtain TIGR4 counts. Error bars represent the standard errors of the means calculated using data from at least three independent experiments. The median (cfu/ml) is shown inside the bars. *statistical significance (p < 0.05) in comparison to wells inoculated only with Sau.
Mentions: Experiments with another Spn reference strain TIGR4, and Sau strain Newman, were also conducted. Whereas, Sau planktonic cells and biofilms reached, 4 h post-inoculation, a bacterial density of ~4.6 × 107 cfu/ml and ~9.8 × 106 cfu/ml, respectively, Sau planktonic cells and biofilms were eradicated (<50 cfu/ml) when they were incubated with strain TIGR4 for 4 h (Figure 2A). TIGR4 planktonic cells, or biofilms, remained unchanged whether incubated alone or with Sau for 4 h (Figure 2B). MRSA strain USA300, Sau ATCC 25923, SAJV01, were also challenged with TIGR4 for 4 h and eradication of both planktonic and biofilms was similarly observed (Figures 2C,D and not shown).

View Article: PubMed Central - PubMed

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 TIGR4&Delta;spxB 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 &gt;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.

No MeSH data available.


Related in: MedlinePlus