Influence of Environmental Stress on the Kinetics and Strength of Attachment of Listeria monocytogenes Scott A to Buna-N Rubber and Stainless Steel

Abstract

Attachment and detachment of Listeria monocytogenes Scott A to Buna-N rubber and stainless Steel under varying conditions of temperature and pH were investigated using model systems. Numbers of attached cells increased with increasing attachment temperature (10 to 45°C) and time (up to 120 min) for both test surfaces. Compared to Buna-N rubber, the rate of attachment to stainless Steel was markedly more rapid for all temperature and pH conditions studied and could not be calculated. Rate of attachment to Buna-N rubber was found to be significantly lower when cells were attached at 10°C. Growth temperature did not significantly affect rates of adhesion to Buna-N rubber. Altering the medium pH during attachment between 4 and 9 demonstrated that rates of adhesion were slower under alkaline conditions. Growth pH was also found to significantly affect rates of attachment to Buna-N rubber. Detachment of cells adhered to Buna-N rubber was significantly affected by growth temperature but not growth pH. Significant differences in detachment were also found between Buna-N rubber and stainless Steel, inferring stronger attachment to Buna-N rubber. Cell surface hydrophobicity was found to be affected by both growth temperature and growth pH. However, changes in hydrophobicity could not be correlated to differences in rates of attachment. Addition of 0.01% trypsin to the attachment medium during cell exposure to either test surface resulted in a 99.9% reduction in the adhered cell population when compared to Controls. This would suggest that proteins play a role in the initial attachment process of L. monocytogenes.