Adhesion and detachment kinetics of several strains of Staphylococcus aureus subsp. aureus under three different...

The kinetics of adhesion of five Staphylococcus aureus subsp. aureus strains (CECT 976, 4459, 4465, 4466 and 5191) to polypropylene at 25 degrees C in the absence of nutrients (PBS medium) were initially compared. Those strains with the highest (CECT 4459) and the lowest (CECT 976) adhesion levels were selected for further studying the effects of a nutrient-rich adhesion-promoting medium (TSB plus 1% glucose-TSBG) as well as of a conditioning film consisting of dried mussel cooking juices (MCJ) on adhesion to and detachment from polypropylene surfaces. Adhesion kinetics were properly described by an empirical model in the absence of conditioning film. The maximum adhesion level was much higher in the presence of TSBG than in PBS, decreasing sharply in both cases after 10-15 h. In contrast, adhesion increased exponentially during 25 h in the presence of dried MCJ. Clear differences were thus found in different media, and it suggests that cleaning strategies should vary under different conditions. The comparison of the adhesion strengths under the different experimental conditions showed that the persistence was highest when biofilms were formed on MCJ, which indicates that cells would remain longer as a source of cross-contamination. Some biofilms were examined by electronic microscopy, and different structures were observed under the different experimental conditions. It is concluded that the study of biofilm formation by S. aureus is necessary to establish efficient control systems in the food industry.