613. Suppression of Daptomycin Resistance Development in Staphylococcus aureus Is a Class Effect of β-Lactams and Is Independent of Daptomycin–β Lactam Synergy

Abstract

Abstract Background Previous studies demonstrate that adding oxacillin during daptomycin (DAP) exposure can prevent DAP resistance development in community-acquired (ST8/USA300) MRSA, presumably by preventing mprF mutation. Hospital-acquired strains, such as MRSA sequence types 5 and 239, typically have higher β-lactam (BL) minimum inhibitory concentrations (MICs) than their community-acquired counterparts and are often less toxigenic, more multidrug-resistant and more refractory to primary antistaphylococcal therapies. It is unknown whether DAP resistance prevention occurs in hospital-acquired MRSA lineages or if augmenting DAP therapy wit..