Adherence of coagulase-negative staphylococci to plastic tissue culture plates: a quantitative model for the adherence of staphylococci to medical devices

Abstract

The adherence of coagulase-negative staphylococci to smooth surfaces was assayed by measuring the optical densities of stained bacterial films adherent to the floors of plastic tissue culture plates. The optical densities correlated with the weight of the adherent bacterial film (r = 0.906; P less than 0.01). The measurements also agreed with visual assessments of bacterial adherence to culture tubes, microtiter plates, and tissue culture plates. Selected clinical strains were passed through a mouse model for foreign body infections and a rat model for catheter-induced endocarditis. The adherence measurements of animal passed strains remained the same as those of the laboratory-maintained parent strain. Spectrophotometric classification of coagulase-negative staphylococci into nonadherent and adherent categories according to these measurements had a sensitivity, specificity, and accuracy of 90.6, 80.8, and 88.4%, respectively. We examined a previously described collection of 127 strains of coagulase-negative staphylococci isolated from an outbreak of intravascular catheter-associated sepsis; strains associated with sepsis were more adherent than blood culture contaminants and cutaneous strains (P less than 0.001). We also examined a collection of 84 strains isolated from pediatric patients with cerebrospinal fluid (CSF) shunts; once again, pathogenic strains were more adherent than were CSF contaminants (P less than 0.01). Finally, we measured the adherence of seven endocarditis strains. As opposed to strains associated with intravascular catheters and CSF shunts, endocarditis strains were less adherent than were saprophytic strains of coagulase-negative staphylococci. The optical densities of bacterial films adherent to plastic tissue culture plates serve as a quantitative model for the study of the adherence of coagulase-negative staphylococci to medical devices, a process which may be important in the pathogenesis of foreign body infections.

Growing and Analyzing Static Biofilms

“…This experimental system, whose most common format is often referred to as the 96-well plate assay, is a simple high-throughput method used to monitor microbial attachment to an abiotic surface. While popularized in the mid-to-late 1990s (Mack et al, 1994;O'Toole et al, 1999), the assay in its typically used form is derived from a protocol published by Christensen et al (1985). Examples of bacteria studied in this manner are listed in Table 1B.1.1, although in theory the protocol could be applied to any bacterial and fungal species amenable to growth in the prescribed format.…”

Tigecycline inhibition of a mature biofilm in clinical isolates ofStaphylococcus aureus: comparison with other drugs: Table 1

“…Each strain was grown in tryptone soy broth (Oxoid), with the addition of 0.25% glucose (TSBG). These assays were performed in microtitre plates as described previously (Christensen et al, 1985;Ziebuhr et al, 1999;Cafiso et al, 2007). Each reported value is the average of 12 measurements at 490 nm.…”

Assessment of ica operon carriage and biofilm production in Staphylococcus epidermidis isolates causing bacteraemia in bone marrow transplant recipients

“…Biofilm production was determined by the method of Christensen et al [9] with some modifications. Isolates were grown overnight in 10 mL of trypticase soy broth (TSB) containing glucose 2.5% w ⁄ v, then diluted 1:200 in fresh TSB.…”

“…Each isolate was tested in eight wells. The lower cut-off was chosen as described by Christensen et al [9], i.e., approximately three standard deviations above the mean of non-inoculated (blank) wells. In total, 112 S. epidermidis isolates were recovered from the blood of 79 patients, of whom 26 were allogeneic BMT recipients and 53 were autologous BMT recipients.…”