87-5 |
Attachment and biofilm formation of Staphylococcus aureus on stainless steel surfaces in the presence of lactic acid bacteria |
R. DEWANTI-HARIYADI1, L. Nuraida1, P. Hariyadi1, and D. Kusumawardani. (1) Department of Food Technology and Human Nutrition, Bogor Agricultural University, P.O. Box 220, Bogor, 16002, Indonesia Attachment and subsequent biofilm formation by pathogen on food processing equipment surfaces could lead to contamination. In fermentation industry, lactic acid bacteria (LAB) are expected to reduce pathogen. It is not known whether LAB affect attachment or biofilm formation by pathogen. Our objective was to evaluate the effect of LAB on the attachment and biofilm formation of Staphylococcus aureus on stainless steel (SS) surfaces. Clinical isolates of Lactobacillus casei, L. casei subsp. rhamnosus and L. acidophilus and food isolates of L. acidophilus, L. bulgaricus, L casei subsp. rhamnosus were used . Individual culture or combination of LAB and staphylococci were allowed to attach for 1 hour and the attached bacteria were enumerated using epifluorescence microscopy. Biofilms were developed in GYE medium for up to 96 hour and enumerated on MRS and BP agar. The number of attached LAB was 3.8 to 4.1 (log CFU/cm2). Clinical isolates of LAB attached better, while S. aureus alone attached best (4.4 log CFU/cm2). When LAB and staphylococci coexisted, decrease in the number of attached cells were observed in all isolates except clinical isolates L. acidophilus and L. casei subsp. rhamnosus . Presence of L. casei inhibited staphylococcal growth resulting in lower density of biofilm. At 96 h, the number of planktonic cells of S. aureus and L. casei were 4.85 and 7.55 log CFU/ml, respectively, while the biofilms were 2.0 and 4.7 log CFU/cm2, respectively. S. aureus was not affected by L. acidophilus . At 96 h, S. aureus and L. acidophilus growth reached 7.8 and 7.7 log CFU/ml, respectively, while the biofilm densities were 4.8 and 4.7 log CFU/cm2, respectively. The results suggest that LABs decrease S. aureus attachment on SS but not necessarily affect biofilm formation. L. casei , but not L. acidophilus inhibited growth and biofilm formation of S. aureus .
Session 87, Food Microbiology: General
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