Biofilm formation by Staphylococcus aureus from food contact surfaces in a meat-based broth and sensitivity to sanitizers

Abstract

This study assessed the capacity of adhesion, the detachment kinetic and the biofilm formation by Staphylococcus aureus isolated from food services on stainless steel and polypropylene surfaces (2 × 2 cm) when cultivated in a meat-based broth at 28 and 7 °C. It was also to study the efficacy of the sanitizers sodium hypochlorite (250 mg/L) and peracetic acid (30 mg/L) in inactivating the bacterial cells in the preformed biofilm. S. aureus strains adhered in high numbers regardless the assayed surface kind and incubation temperature over 72 h. Cells detachment of surfaces revealed high persistence over the incubation period. Number of cells needed for biofilm formation was noted at all experimental systems already after 3 days. Peracetic acid and sodium hypochlorite were not efficient in completely removing the cells of S. aureus adhered on polypropylene and stainless steel surfaces. From these results, the assayed strains revealed high capacity to adhere and form biofilm on polypropylene and stainless steel surfaces under different growth conditions. Moreover, the cells in biofilm matrix were resistant for total removal when submitted to the exposure to sanitizers.

Keywords: Staphylococcus aureus; biofilm; cross-contamination; food processing environment; sanitizers.

Figure 1

Kinetics of adhesion of S. aureus S3, S28 and S5 cells to polypropylene and stainless steel surfaces in meat-based broth at 7 °C and 28 °C.

Figure 2

Kinetics of separation of S. aureus S3, S28 and S5 cells after 24, 48 and 72 hours of polypropylene and stainless steel surfaces in meat-based broth at 7 °C and 28 °C.

Figure 3

Biofilm formation by S. aureus S3 cells on polypropylene and stainless steel surfaces in meat-based broth at 7 °C and 28 °C over 15 days of incubation. Dotted line means the lower bacterial count (cfu/cm²) needed for biofilm formation according to Ronner et al. (1993) and Wirtanen et al. (1995).

Figure 4

Scanning electronic microphotography of S. aureus S3 cells adhered on polypropylene (A, B, C) and stainless steel (D, E, F) when incubated in meat-based broth at 28 °C for 15 days, after the application of water (A, D - control), peracetic acid (B,E) and sodium hypochlorite (C, F). Different magnifications were used for better visualization.