Biofilm formation and presence of the intercellular adhesion locus ica among staphylococci from food and food processing environments

Summary

In clinical staphylococci presence of the ica genes and biofilm formation are considered important for virulence. Biofilm formation may also be of importance for survival and virulence in food related staphylococci. In the present work staphylococci from the food industry were found to vary widely in their ability to form biofilm on polystyrene. Seven and 21 of 144 food related strains were found to be strong and weak biofilm formers, respectively. Glucose and sodium chloride stimulated biofilm formation. The biofilm forming strains belonged to nine different coagulase negative species of Staphylococcus. The icaA gene of the intercellular adhesion locus was detected by Southern blotting and hybridization in 38 of 67 food related strains tested. The presence of icaA was positively correlated with strong biofilm formation. The icaA gene was partly sequenced for 22 food related strains from nine different species of Staphylococcus, and their icaA genes were found to have a DNA similarity of 69-100% to previously sequenced icaA genes. Northern blot analysis indicated that the expression of the ica genes was higher in strong biofilm formers compared to strains not forming biofilms. Biofilm formation on polystyrene was positively correlated with biofilm formation on stainless steel and with resistance to quaternary ammonium compounds, a group of disinfectants.