CHANGES IN THE STRENGTH OF ATTACHMENT OF MICROORGANISMS TO SURFACES FOLLOWING TREATMENT WITH DISINFECTANTS AND CLEANSING AGENTS

Suspensions of Pseudomonas aeruginosa and Staphylococcus epidermidis, and biofilms established (16 h) on submerged glass and stainless steel (216 2B) coupons, were exposed to sodium hypochlorite (0.02% or 0.015 % w/v),-Dodigen (0.0015% w/v or 0.0006% w/v), sodium dodecylsulphate ( 6% w/v or 0.1% w/v) and Tween-80 (6% w/v) for 5 min at 20 degrees C. S urvival was assessed by viable counts and blot succession. Biofilm bac teria were significantly less susceptible to these biocides than were planktonic cells, but their attachment to the surfaces was loosened by such treatments. Treatment with the non-ionic surfactant, Tween-80, h owever, strengthened the attachment of Staph. epidermidis to stainless steel. Such effects on attachment strength, which are species and sur face dependent, have profound implications on post-treatment cleansing and possible re-contamination of product in clean-in-place (CIP) syst ems.