The influence of temperature on the adhesion of mixed cultures of Staphylococcus aureus and Escherichia coli to polypropylene

The adhesion of Staphylococcus aureus and Escherichia coli, in mixed cultures to polypropylene surfaces was evaluated at 12 degrees C and 30 degrees C. The micro-organisms were isolated from a chicken carcass and cultured in an aqueous extract, prepared from the same carcass, for the production of biofilms on poly-propylene coupons. Adhered cells were counted by epifluorescence microscopy with acridine orange staining. Escherichia coli adhered in greater numbers to the coupons than S. aureus at both temperatures. Staphylococcus aureus adhered better at 12 degrees C than at 30 degrees C, while the reverse was true for E. coli. At 30 degrees C, there was no increase in the number of adherent cells of S. aureus over 8 h, while E. coli increased from a median of 5.0-19.0 per microscope field At 12 degrees C, the major increase in adherent cell numbers for both species occurred between 2 and 4 h, so that leaving cleaning until 8 h, as is common, would not result in greatly increased biofilms, a-hourly cleansing is clearly unrealistic. However, total adherent cell numbers were the same at 12 degrees and 30 degrees C between 4 and 6 h incubation. Hence it seems that reduced temperature has little to offer for restricting biofilm formation on polypropylene work surfaces in a well-run food processing plant. (C) 2000 Academic Press.