1194. Identification and Characterization of Extracellular Inducers of Persistence in Staphylococcus epidermidis and Staphylococcus aureus

BACKGROUND: This study describes the identification and partial characterization of persistence inducing factors (PIF) from Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). Persistence is an epigenetic process that results in tolerance of bacterial cells to antibiotic treatment, which can result in chronic human infections. METHODS: Others have demonstrated a significant increase in persister numbers during mid-log phase. Inducers of this mid-log increase have yet to be identified in staphylococci. Optical density at 600 nm (OD(600)) was used instead of time to determine when persister numbers increased during logarithmic growth. Concentrated culture filtrates (CCF) from S. epidermidis RP62A and S. aureus SH1000 were obtained at various OD(600)’s and following incubation at 16 h. The CCF’s were used to develop a persistence inducing factor (PIF) assay. The PIF assay was used to partially characterize PIF from S. epidermidis RP62A and S. aureus SH1000 for relative molecular weight, temperature and protease sensitivity and inter-species communications. RESULTS: Optimal OD(600)’s for the S. epidermidis RP62A and S. aureus SH1000 PIF assays were 2.0 and 0.5, respectively. The highest PIF activity for both species was from CCF following incubation overnight (16 h). S. epidermidis RP62A’s PIF activity was decreased by storage at 4(o) C (2 weeks or longer) but not following incubation at 20(o) C (16 h), 37(o) C (1 h) or 100(o) C (15 min). S. aureus SH1000’s PIF activity was decreased following storage at 4(o) C (2 week or longer) and after boiling at 100(o)C for 5 min but not after incubation at 37(o) C (1 h). PIF activity from both species was less than 3,000 Mrr. Proteinase-K treatment of S. aureus SH1000 PIF decreased activity but did not decrease PIF activity of S. epidermidis RP62A. PIF from S. epidermidis RP62A did not increase persister numbers when used to treat S. aureus SH1000 cells nor did PIF from S. aureus SH1000 increase persister numbers in S. epidermidis RP62A cells. CONCLUSION: Previous attempts to discover PIF’s for staphylococcal species were unsuccessful due to the time-based means used to identify mid-log. Both staphylococcal species appear to produce unique, extracellular, low-molecular-weight inducers of persistence (PIF) when assayed using an OD(600)-based PIF assay. DISCLOSURES: All Authors: No reported disclosures