Inhibition of Staphylococcus aureus by antimicrobial biofilms formed by competitive exclusion microorganisms on stainless steel

• Antimicrobial activity of CE biofilms on stainless steel to S. aureus was determined.
• Three CE microorganisms inhibitory to S. aureus were isolated and identified.
• CE microorganisms formed biofilms on stainless steel surfaces at 25 °C within 24 h.
• Resistance of CE microorganisms to desiccation was enhanced after biofilm formation.
• Antimicrobial activity of CE microorganisms was maintained after biofilm formation.

The goal of this study was to develop a desiccation resistant antimicrobial surface using biofilm of competitive exclusion (CE) microorganism inhibitory to Staphylococcus aureus. We isolated 161 microorganisms from soils, foods, and food-contact surfaces that are inhibitory to S. aureus. Among them, three CE microorganisms (Streptomyces spororaveus strain Gaeunsan-18, Bacillus safensis strain Chamnamu-sup 5–25, and Pseudomonas azotoformans strain Lettuce-9) exhibiting strong antibacterial activity and high growth rates were selected for evaluation. These isolates formed biofilms within 24 h on stainless steel coupons (SSCs) immersed in Bennet's broth and tryptic soy broth at 25 °C. Cells in these biofilms showed significantly (P ≤ 0.05) enhanced resistance to a desiccation (43% relative humidity [RH]) compared to those attached to SSCs but not in biofilms. The antimicrobial activities of biofilms formed by these isolates on SSCs against S. aureus at 25 °C and 43% RH were determined. Compared to SSCs lacking biofilms formed by CE microorganisms, populations of S. aureus on SSCs harboring CE biofilms were significantly lower (P ≤ 0.05). Results indicate that persistent antimicrobial activity against S. aureus on stainless steel surfaces can be achieved by the presence of biofilms of CE microorganisms. This information will be useful when developing strategies to improve the microbiological safety of foods during storage, processing, and distribution by facilitating the development of effective antimicrobial food-contact surfaces.