ATTACHMENT AND BIOFILM FORMING ABILITIES OF PERSISTENT AND NON-PERSISTENT LISTERIA MONOCYTOGENES ISOLATES by ARPAN R. BHAGAT

NON-PERSISTENT LISTERIA MONOCYTOGENES ISOLATES by ARPAN R. BHAGAT (Under the Direction of JOSEPH F. FRANK) ABSTRACT Attachment and biofilm formation by 27 selected strains of Listeria monocytogenes that had been isolated from a chicken further processing plant were determined. One objective was to determine whether the persistent L. monocytogenes isolates demonstrated different attachment and biofilm formation than the non-persistent isolates. Second objective was to establish the microtiter plate assay as a rapid screening method for the attachment and biofilm forming ability. Persistent and non-persistent Listeria isolates showed similar attachment to the hydrophilic and hydrophobic microtiter plates as well as on stainless steel coupons (p<0.05). Only one persistent Listeria isolate exhibited significantly greater (p<0.05) biofilm formation than the non-persistent genotypes in both high and low nutrient media and on hydrophobic and hydrophilic surfaces. The results indicate that significant phenotypic variation occurs within persistent genotypes. Data obtained using the microtiter plate assay highly correlated (p<0.0001) with the data for the bacterial attachment and biofilm formation on stainless steel.