Bioluminescent assay for measurement of bacterial attachment to polyethylene

Abstract

A bioluminescent method for measuring the number of bacteria attached to synthetic polymers was developed with strains of S. epidermidis and S. aureus. The method was optimized with respect to extraction of bacterial ATP and time of incubation of synthetic polymer with bacterial strains. The attachment to polyethylene was a rapid process and a measurable amount of attached bacteria was obtained within 5 min but a standard assay required 1 h incubation to reach a constant amount of attached cells. Longer incubation did not result in an increase in the number of adhering organisms. At <10 10 CFU/ml the number of attached bacteria increased with the concentration of bacteria, while at ⩾10 10 CFU/ml the number of attached bacteria became independent of the concentration. The maximum number of attached bacteria was 2.5 × 10 7 cells/cm 2 of polyethylene. The bioluminescent method for measuring bacterial attachment correlated well with the widely used microscopic technique. Furthermore, this method was rapid, simple, time saving and more convenient than the microscopic technique and suitable for automation. In contrast to the microscopic technique a bioluminescent method for determining bacterial attachment can also be applied to a great variety of materials having irregular surfaces such as catheters and wound dressings.