The use of a model system to compare the efficiency of ultrasound and agitation in the recovery of Bacillus subtilis spores from polymer surfaces.

The effectiveness of ultrasound and mechanical agitation for the recovery of Bacillus subtilis spores from pre-inoculated glass, polystyrene, polypropylene, polyethylene and polycarbonate surfaces was tested in the presence and absence of surfactant. Recovery from polymers was improved by the use of surfactant. Simple agitation, as frequently used in bioburden determination, is shown to be a poor method for the recovery of spores from hard surfaces. The use of ultrasound achieves recoveries over 90% only with glass, recoveries from polymers ranging from 40%-75%. Recoveries from polypropylene and polycarbonate showed poor reproducibilities. Agitation with Ballotini beads improved the reproducibility of recoveries from polymers and also in the majority of cases improved recovery levels.