Antimicrobial effects of probiotics against selected pathogenic and spoilage bacteria in cheese-based dips

Abstract

Spot-on lawn, spot and streak, co-culturing techniques and HPLC analysis were used
\nfor the detection and screening of inhibitory activity produced by probiotic bacteria against
\nspoilage and pathogenic bacteria. After incubation, plates were examined for either zones of
\ninhibition and for other effects of suppression around the wells/spots and streaks or cfu/g of
\ntarget bacteria. The spore-formers were inhibited by the probiotic organisms to a greater extent
\nthan the non-spore formers. The inhibitory effect of all probiotic bacteria was weakest against E.
\ncoli and strongest against B. cereus. S. aureus was inhibited to a greater extend by B. animalis
\nand by L. rhamnosus. The order of probiotic bacteria in terms of level of inhibition on agar plates
\n(and zone of inhibition in mm) was L. rhamnosus (21)> L. acidophilus (19) = L. casei (19) > L.
\nparacasei subsp. paracasei (18) > B. animalis (15) > P. freudenreichii subsp. shermanii (11).
\nThough co-culturing of target organisms with probiotic bacteria in reconstituted skim milk
\nshowed inhibitory effect against target organisms; however, in French onion dip, there was no
\nadditive effect in controlling the bacterial population except that for B. cereus. Varying
\nquantities of organic acids (acetic, lactic, formic, propionic, butyric, benzoic and phenyllactic)
\nthat were responsible for the inhibition were detected.