Effect of temperature and growth media on the attachment of Listeria monocytogenes to stainless steel.

Listeria monocytogenes ATCC 19111 cultivated in nutrient-rich medium (brain heart infusion, BHI) or starved in minimal medium (10% filter sterilized pond water and 90% sterilized distilled water) were investigated for their initial attachment to austenitic stainless steel No. 4 with satin finish at 4 degrees C, 20 degrees C, 30 degrees C, 37 degrees C, or 42 degrees C. A droplet (10 microl) containing approximately 10(7) CFU/ml of L. monocytogenes suspended in BHI or minimal medium was placed on the stainless steel surface. After holding in saturated humidity for 3 h at the desired temperature the surface was washed and prepared for scanning electron microscopy (SEM). Using SEM, attachment of L. monocytogenes was determined by counting cells remaining on the surface. When L. monocytogenes cultivated in BHI were used, with the exception of the number of attached cells being lower at 42 degrees C than at 37 degrees C and 30 degrees C, the number of attached cells increased with increasing temperature (P<0.05). When L. monocytogenes starved in minimal medium were used, the number of attached cells also increased with increasing attachment temperature (P<0.05), but the number of attached cells at 42 degrees C was lower than that at the other temperatures. The attachment of L. monocytogenes to stainless steel surface was greater when cultivated in rich medium of BHI vs starved in the minimal medium.