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Updated: Oct 22, 2025
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Published on: June 8, 2022
Free-Floating Aggregate and Single-Cell-Initiated Biofilms of Staphylococcus aureus
Tripti Thapa Gupta1, Niraj K Gupta1, Peter Burback2
1Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA.
Abstract:
Periprosthetic joint infection (PJI) occurring after artificial joint replacement is a major clinical issue requiring multiple surgeries and antibiotic interventions. Staphylococcus aureus is the common bacteria responsible for PJI. Recent in vitro research has shown that staphylococcal strains rapidly form free-floating aggregates in the presence of synovial fluid (SF) with biofilm-like resistance to antimicrobial agents. However, the development of biofilms formed from these aggregates under shear have not been widely investigated. Thus, in this study, we examined the progression of attached biofilms from free-floating aggregates. Biofilms were grown for 24 h in flow cells on titanium discs after inoculation with either pre-aggregated or single planktonic cells. Image analysis showed no significant difference between the biofilm formed from aggregates vs. the planktonic cells in terms of biomass, surface area, and thickness. Regarding antibiotic susceptibility, there were 1 and 2 log reductions in biofilms formed from single cells and aggregates, respectively, when treated with vancomycin for 24 h. Thus, this study demonstrates the formation of biofilm from free-floating aggregates and follows a similar developmental time period and shows similar antibiotic tolerance to more traditionally inoculated in vitro flow cell biofilms.
Insights
Staphylococcus aureus forms aggregates in synovial fluid, leading to biofilms that resist antibiotics. This study shows these biofilms develop similarly to planktonic cell biofilms, offering insights into periprosthetic joint infection treatment.
Area of Science:
- Microbiology
- Biomedical Engineering
- Infectious Diseases
Background:
- Periprosthetic joint infection (PJI) is a significant complication of artificial joint replacement.
- Staphylococcus aureus is a primary pathogen in PJI, forming biofilms that resist antimicrobial treatments.
- The development of biofilms from staphylococcal aggregates in synovial fluid under shear stress is not well understood.
Purpose of the Study:
- To investigate the progression of biofilms formed from Staphylococcus aureus aggregates under shear conditions.
- To compare the characteristics and antibiotic susceptibility of biofilms derived from aggregates versus planktonic cells.
Main Methods:
- Biofilms were cultivated in flow cells on titanium discs for 24 hours.
- Inoculation was performed using either pre-aggregated or single planktonic Staphylococcus aureus cells.
- Biofilm biomass, surface area, thickness, and antibiotic susceptibility (vancomycin) were analyzed.
Main Results:
- No significant differences were observed in biofilm biomass, surface area, or thickness between biofilms formed from aggregates and single cells.
- Biofilms formed from aggregates showed a slightly greater reduction in viable cells (2 log) compared to single-cell biofilms (1 log) after vancomycin treatment.
Conclusions:
- Staphylococcus aureus aggregates in synovial fluid can initiate biofilm formation with characteristics similar to those from planktonic cells.
- These biofilms exhibit comparable antibiotic tolerance, highlighting potential challenges in treating PJI caused by aggregated bacteria.
