EFFECT OF ENVIRONMENTAL-STRESS ON THE ABILITY OF LISTERIA-MONOCYTOGENES SCOTT-A TO ATTACH TO FOOD CONTACT SURFACES

Attachment of Listeria monocytogenes Scott A to Buna-N rubber and stai nless steel under different temperature and pH conditions at the time of cell growth or at the time of attachment was investigated. All expe riments were conducted using sterile phosphate buffer to avoid cell gr owth during exposure to the test surfaces. Numbers of attached cells i ncreased with increasing attachment temperature (10 to 45 degrees C) a nd exposure time for both test surfaces. Maximum levels of attached ce lls were obtained when cell growth occurred at 30 degrees C. Downward, but not upward, shifts in the cell suspension holding temperature pri or to attachment to Buna-N rubber resulted in reduced adhered cell pop ulations. Maximum levels of adhered cells to Buna-N rubber were not af fected by adjustments of the attachment medium pH between 4 and 9. How ever, after short contact times (i.e., less than 30 min), levels of at tached cells were lower when attachment occurred under alkaline condit ions. Growth pH was also found to affect the levels of adhered cell po pulations to Buna-N rubber. L. monocytogenes Scott A attached to stain less steel at higher levels for all temperature and pH parameters eval uated in this study.