In vivo development of heterogeneous glycopeptide-intermediate Staphylococcus aureus (hGISA), GISA and daptomycin resistance in a patient with meticillin-resistant S. aureus endocarditis

We report a patient who developed a meticillin-resistant Staphylococcus aureus (MRSA) central venous catheter infection complicated by infective endocarditis. The patient was initially treated with glycopeptides, which led to the development of heterogeneous glycopeptide resistance, the detection of which required the use of a macro Etest screening test. Subsequently, the causative strain, confirmed by PFGE as a UK epidemic MRSA-15, was treated with daptomycin, and again resistance developed in vivo. The development in vivo of resistance to both these agents suggests that the resistance mechanisms may be associated. We suggest that the clinician managing MRSA infection should anticipate daptomycin resistance when reduced glycopeptide susceptibility is detected.