Prevalence, molecular epidemiology, and clinical significance of heterogeneous glycopeptide-intermediate Staphylococcus aureus in liver transplant recipients

We investigated the prevalence, molecular epidemiology, and clinical significance of heterogeneous glycopeptide-intermediate Staphylococcus aureus (hGISA) isolates in 48 liver transplant recipients infected or colonized with methicillin-resistant S. aureus over a 5-year period. Strains were screened for hGISA on Mueller-Hinton agar containing 5 mg of teicoplanin per liter. Heterogeneous glycopeptide resistance was confirmed by the E-test method with a dense inoculum and a simplified method of population analysis. hGISA strains were found in 13 (27%) of the 48 patients studied. Eleven of the 13 strains shared a common multiresistant phenotype with homogeneous methicillin resistance and gentamicin resistance, and they were closely related according to the results of pulsed-field gel electrophoresis. Only 2 of the 13 patients infected or colonized with hGISA strains had previously received glycopeptide therapy. Most patients were successfully treated with vancomycin, but one patient who failed to respond to vancomycin subsequently died. These results suggest that the high prevalence of hGISA among our patients was due to the clonal spread of a multiresistant strain.