S22: Impact of competition between Staphylococcus epidermidis and Staphylococcus aureus on biofilm formation of stainless steel surfaces

If hospital nurseries are found to support populations of virulent Staphylococcus aureus strains, resident infants may be intentionally infected with less virulent strains of Staphylococcus epidermidis. By occupying the same niche, S. epidermidis blocks S. aureus infections. The purpose of this research was to determine if the same competition occurs on stainless steel. To assess biofilm formation sterile stainless steel disks, suspended in nutrient broth, were separately exposed to pure cultures of S. epidermidis and to pure cultures of S. aureus. To determine competition disks initially exposed to S. epidermidis were incubated to establish biofilms then exposed to S. aureus. In all experiments the disks were aseptically retrieved and scraped to remove the organisms. The scrapings were serially diluted, plated on nutrient agar, and incubated. The distintive colonial characteristics of the two organisms allowed for differential plate counts which were statistically analyzed. Both organisms were found to be equally adept at biofilm formation. Previously formed S. epidermidis biofilms were found to significantly decrease the attachment of S. aureus.