Genotypic Resistance Testing Creates New Treatment Challenges: Two Cases of Oxacillin-Susceptible Methicillin-Resistant Staphylococcus aureus

Oxacillin-susceptible, mecA-positive Staphylococcus aureus isolates create a treatment challenge for the clinician. In this article, we describe two cases of bacteremia from isolates that carried the mecA gene but were susceptible to oxacillin (oxacillin-susceptible methicillin-resistant S. aureus [OS-MRSA]). DNA microarray analysis was used to characterize these isolates as a mecA-positive, clonal complex 5, pediatric strain and a mecA-positive, clonal complex 8, USA300 strain.