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The attachment of Listeria monocytogenes isolates Scott A and Jalisco Cheese to stainless steel surfaces at 35", 21", and 10°C was investigated using scanning electron microscopy (SEM). Cells were found to adhere at all three temperatures, but cells with fibrils were observed only at 21°C. When grown at pH 8, the attachment matrix was more prevalent at 21°C than at 35°C and may also be related to the length of incubation time at 21°C. It appears that adherence may be related to the flagella and any exopolymer surrounding the cells.

Listeria monocytogenes serotype 3a and Pseudomonas fragi ATCC 4973 were examined for attachment capability and biofilm development on glass coverslips under flowing systems. Tryptic soy broth supplemented with yeast extract was the growth medium. A continuous flow slide chamber was developed for in situ observations using phase-contrast microscopy. Glass coverslips were examined by epifluorescent and scanning electron microscopy for biofilm formation. The ultrastructure of attached test organisms was examined for the presence of exopolymers using transmission electron microscopy. In pure cultures, attachment of L. monocytogenes to glass coverslips was sparse, while P. fragi accumulated on glass coverslips as a confluent layer of cells. When L. monocytogenes was grown in mixed culture with P. fragi, an exopolymer-producing microorganism, attachment and microcolony formation by L. monocytogenes was enhanced. Results suggest that under flowing conditions the presence of an exopolymer-producing microorganism may be more important than hydrophobicity, surface charge, or flagellar movement in attachment of L. monocytogenes to inert surfaces.