Institute of Chemical Technology Prague Department of Food Preservation and Meat Technology Effect of physicochemical surface characteristics on bacterial attachment Petra Sedláčková

Bacterial adhesion x Biofilm formation effect of surface characteristic microorganism used for attachment – widely described in nature, isolated in food processing environments

Microorganisms Pseudomonas fluorescens (DBM 3113 BHA) gram-negative, aerobic bacterium, cat.+, ox.+ scanning electron micrographs of Pseudomonas biofilm formation

Escherichia coli (DBM 3125 BHA) gram-negative, cat.+, ox.- scanning electron micrograph of E. coli biofilm formation

Asaia bogorensis gram-negative, aerobic bacterium, cat.+, ox.- scanning electron micrographs of A. bogorensis biofilm formation

Tested surfaces stainless steel – AIS 304 40 x 40 mm, tested area 13 x 13 mm the slides were washed in sanitizers solution, rinsed by distilled water and autoclaved at 121 °C for 20 min

glass – for the microbial purpose 76 x 26 mm, tested area 13 x 13 mm the slides were washed for 30 min in sanitizers solution, rinsed by distilled water , were placed on aluminium foil, covered and autoclaved at 121 °C for 20 min

evaluation incubation (3,6,12,24 hr) rinsing by sterile nutrient broth + addition nutrient broth incubation (24 hr) 100 μl evaluation

bacteria were scraped from test surfaces with a cotton-wool swab transferred into test tube containing 10 ml physiological solution stirred for 1 min to release the cells into the solution agar agar Cultivation on agar: P. fluorescens: 25 °C, 24 hr, A. bogorensis 25 °C, 48 hr, E. coli 37 °C, 24 hr

Attachment of P. fluorescens, A. bogorensis, E Attachment of P. fluorescens, A. bogorensis, E. coli on stainless steel and glass Detection limit 2,9 * 10 -1 CFU * cm -2

a) 3, 6 ,12 ,24 attachment of Asaia bogorensis b) 3, 6 ,12 ,24 attachment of Pseudomonas fluorescens detection limit 2,9 * 10 -1 CFU * cm -2 c) 3, 6 ,12 ,24 attachment of Escherichia coli

attachment of all tested microorganisms on stainless steel x glass Detection limit 2,9 * 10 -1 CFU * cm -2

Conclusion P. fluorescens at 3 hr incubation had higher attachment values compared to other tested microorganisms. Cell numbers for 24 hr biofilms are significantly different between P. fluorescens and Escherichia coli. No significant effect of initial attachment on biofilm growth (for each microorganism) between stainless steel and glass was found.