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

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 c ultures of Staphylococcus epidermidis (SE), at various growth-limiting nutr ient concentrations, in the absence of any fabric, indicated a maximum cult ure growth rate constant mu (max) = 0.78 +/- 0.02 h(-1). Batch experiments for Control fabric samples indicated that SE cultures exhibited about the s ame suspended cell growth rate (0.72 +/- 0.02 h(-1)) as observed in batch s uspended 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. Gr owth rates of suspended SE cultures were 5-6 times higher in the fluid phas e 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-coate d fabric. In all batch colonization experiments, both live and dead SE bact erial cells accumulate on the surfaces of both silver-coated and Control fa brics. Adherent viable SE cells accumulated to 1-2 orders of magnitude more (similar to5 x 10(+8) cells/cm(2)) on Control fabric than SE cells on the silver-coated fabric (similar to1.1 x 10(+6) cells/cm(2)), respectively. Be tween 70-95% SE cells on the Control fabric were viable, while on the silve r-coated fabric samples, at 24 h, viable cells were less than 10% of the ad herent community (i.e., greater than 90% nonviable cells). In flow cell col onization experiments, SE cells accumulated on Control fabric to a maximum adherent cell concentration of 6 x 10(+7) - 8 x 10(+7) cells/cm(2) by 24 h with the proportion of viable cells remaining relatively constant at 76% th roughout an experiment. Both noninvasive microscopic enumeration and destru ctive assays gave the same results for adherent cell numbers. Using silver- coated fabric, total cells numbers (live + dead) reached a level of similar to1.1 x 10(+7) - 3.0 x 10(+7) cells/cm(2) after about 6 h and remained con stant. However, while the proportion of viable cells initially on the surfa ce 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 signific antly lower than on Control fabric. (C) 2000 John Wiley & Sons, Inc.