Efficacy of silver-coated fabric to prevent bacterial colonization and subsequent device-based biofilm formation

Abstract

Efficacy of silver‐coated poly(ethylene terephthalate) to prevent bacterial attachment and subsequent infection was quantified in vitro, in both batch‐ and flowing‐fluid experiments. Kinetic analysis of batch suspended cell cultures of Staphylococcus epidermidis (SE), at various growth‐limiting nutrient concentrations, in the absence of any fabric, indicated a maximum culture growth rate constant μ_max = 0.78 ± 0.02 h⁻¹. Batch experiments for Control fabric samples indicated that SE cultures exhibited about the same suspended cell growth rate (0.72 ± 0.02 h⁻¹) as observed in batch suspended cultures without fabric. Suspended SE cultures in the presence of silver‐coated fabric grew at a considerably lower rate, 0.15 ± 0.01 h⁻¹, indicating the inhibitory effect of Ag⁺² ion released from the fabric. Growth rates of suspended SE cultures were 5–6 times higher in the fluid phase in contact with the Control fabric compared to cultures exposed to silver‐coated fabric. Maximum suspended cell concentrations attained at time = 24 h were 1–2 orders of magnitude higher for Control fabrics vs. silver‐coated fabric. In all batch colonization experiments, both live and dead SE bacterial cells accumulate on the surfaces of both silver‐coated and Control fabrics. Adherent viable SE cells accumulated to 1–2 orders of magnitude more (∼5 × 10⁺⁸ cells/cm²) on Control fabric than SE cells on the silver‐coated fabric (∼1.1 × 10⁺⁶ cells/cm²), respectively. Between 70–95% SE cells on the Control fabric were viable, while on the silver‐coated fabric samples, at 24 h, viable cells were less than 10% of the adherent community (i.e., greater than 90% nonviable cells). In flow cell colonization experiments, SE cells accumulated on Control fabric to a maximum adherent cell concentration of 6 × 10⁺⁷ − 8 × 10⁺⁷ cells/cm² by 24 h with the proportion of viable cells remaining relatively constant at 76% throughout an experiment. Both noninvasive microscopic enumeration and destructive assays gave the same results for adherent cell numbers. Using silver‐coated fabric, total cells numbers (live + dead) reached a level of ∼1.1 × 10⁺⁷ − 3.0 × 10⁺⁷ cells/cm² after about 6 h and remained constant. However, while the proportion of viable cells initially on the surface was 63–75%, this fraction dropped continuously during each experiment to less than 6% viable cells at 24 h. Regardless of the criteria, the number of viable or nonviable cells attached to silver‐coated fabric were significantly lower than on Control fabric. © 2000 John Wiley & Sons, Inc. Biomed Mater Res (Appl Biomater) 53: 621–631, 2000