Interplay of antibiotics and bacterial inoculum on suture-associated biofilms

• Published in: The Journal of surgical research 2012-10, Vol.177 (2), p.334-340
• Main Authors: Hess, Donavon J., MD, PhD, Henry-Stanley, Michelle J., PhD, Wells, Carol L., PhD
• Format: Article
• Language: English
• Subjects: Ampicillin; Ampicillin - pharmacology; Ampicillin - therapeutic use; Anti-Bacterial Agents - pharmacology; Anti-Bacterial Agents - therapeutic use; Antibiotics; Biofilm; Biofilms - drug effects; Biomass; Confocal microscopy; Microbial Sensitivity Tests; Microscopy, Confocal; Oxacillin; Oxacillin - pharmacology; Oxacillin - therapeutic use; Staphylococcal Infections - prevention & control; Staphylococcus aureus; Staphylococcus aureus - drug effects; Surgery; Surgical Wound Infection - prevention & control; Suture; Sutures - microbiology; Vancomycin; Vancomycin - pharmacology; Vancomycin - therapeutic use
• ISSN: 0022-4804; 1095-8673
• DOI: 10.1016/j.jss.2012.04.040

Abstract Background Biofilms are often antibiotic resistant, and it is unclear if prophylactic antibiotics can effectively prevent biofilm formation. Experiments were designed to test the ability of high (bactericidal) concentrations of ampicillin (AMP), vancomycin (VAN), and oxacillin (OXA) to prevent formation of suture-associated biofilms initiated with low (104 ) and high (107 ) numbers of Staphylococcus aureus. Materials and methods S. aureus biofilms were cultivated overnight on silk suture incubated in biofilm growth medium supplemented with bactericidal concentrations of AMP, VAN, or OXA. Standard microbiological methods were used to quantify total numbers of viable suture-associated S. aureus . Crystal violet staining followed by spectroscopy was used to quantify biofilm biomass, which includes bacterial cells plus matrix components. To observe the effects of antibiotics on the microscopic appearance of biofilm formation, biofilms were cultivated on glass slides, then stained with fluorescent dyes, and observed by confocal microscopy. Results In the presence of a relatively low inoculum (104 ) of S. aureus cells, bactericidal concentrations of AMP, VAN, or OXA were effective in preventing development of suture-associated biofilms. However, similar concentrations of these antibiotics were typically ineffective in preventing biofilm development on sutures inoculated with 107 S. aureus , a concentration relevant to contaminated skin. Confocal microscopy confirmed that bactericidal concentrations of AMP, VAN, or OXA inhibited, but did not prevent, development of S. aureus biofilms. Conclusion Bactericidal concentrations of AMP, VAN, or OXA inhibited formation of suture-associated biofilms initiated with low numbers (104 ), but not high numbers (107 ), of S. aureus cells.