title: Reduced ability to detect surface-related biofilm bacteria after antibiotic exposure under in vitro conditions.
abstract: Background and purpose - Antibiotic treatment of patients before specimen collection reduces the ability to detect organisms by culture. We investigated the suppressive effect of antibiotics on the growth of non-adherent, planktonic, and surface-related biofilm bacteria in vitro by using sonication and microcalorimetry methods. Patients and methods - Biofilms of Staphylococcus aureus, S. epidermidis, Escherichia coli, and Propionibacterium acnes were formed on porous glass beads and exposed for 24 h to antibiotic concentrations from 1 to 1,024 times the minimal inhibitory concentration (MIC) of vancomycin, daptomycin, rifampin, flucloxacillin, or ciprofloxacin. The beads were then sonicated to dislodge biofilm, followed by culture and measurement of growth-related heat flow by microcalorimetry of the resulting sonication fluid. Results - Vancomycin did not inhibit the heat flow of staphylococci and P. acnes at concentrations ≤1,024 μg/mL, whereas flucloxacillin at >128 μg/mL inhibited S. aureus. Daptomycin inhibited heat flow of S. aureus, S. epidermidis, and P. acnes at lower concentrations (32-128 times MIC, p < 0.001). Rifampin showed inconsistent results in staphylococci due to random emergence of resistance, which was observed at concentrations ≤1,024 times MIC (i.e. 8 μg/mL). Ciprofloxacin inhibited heat flow of E. coli at ≥4 times MIC (i.e. ≥ 0.06 μg/mL). Interpretation - Whereas time-dependent antibiotics (i.e. vancomycin and flucloxacillin) showed only weak growth suppression, concentration-dependent drugs (i.e. daptomycin and ciprofloxacin) had a strong suppressive effect on bacterial growth and reduced the ability to detect planktonic and biofilm bacteria. Exposure to rifampin rapidly caused emergence of resistance. Our findings indicate that preoperative administration of antibiotics may have heterogeneous effects on the ability to detect biofilm bacteria.
authors: a Department of Orthopaedic Surgery and Traumatology , Odense University Hospital.|b Institute of Clinical Research, University of Southern Denmark , Odense , Denmark.
authors: Christen
authors: C
authors: Ravn
authors: c Septic Surgical Unit.
authors: Ulrika
authors: U
authors: Furustrand Tafin
authors: d Infectious Diseases Service, Department of Medicine , Lausanne University Hospital , Lausanne , Switzerland.
authors: Bertrand
authors: B
authors: Bétrisey
authors: a Department of Orthopaedic Surgery and Traumatology , Odense University Hospital.|b Institute of Clinical Research, University of Southern Denmark , Odense , Denmark.
authors: Søren
authors: S
authors: Overgaard
authors: e Center for Musculoskeletal Surgery , Charité - University Medicine Berlin , Berlin , Germany.
authors: Andrej
authors: A
authors: Trampuz
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D001419:Bacteria / Q000187:drug effects*; D018441:Biofilms / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008826:Microbial Sensitivity Tests; D016459:Prosthesis-Related Infections / Q000188:drug therapy* / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents