Oral fusidic acid fails to eradicate methicillin-resistant Staphylococcus aureus colonization and results in emergence of fusidic acid-resistant strains

Carriers of methicillin-resistant Staphylococcus aureus (MRSA) in hospital constitute a reservoir of infections and increase the risk of bacteremia an d wound infection. In this prospective randomized trial, we tested the effe ctiveness of oral fusidic acid for eradication of MRSA colonization. From M arch 1997 through February 1998, patients with MRSA colonization in medical intensive care units in a large urban teaching hospital were randomly assi gned to receive fusidic acid 500 mg q8h orally for 7 days or no anti-staphy lococcal treatment. Twenty-three MRSA carriers were found during the study period and 16 were eligible for evaluation; six of them received fusidic ac id. MRSA colonization was cleared in only two of the six patients with fusi dic acid treatment, and later recurred in one of them. MRSA disappeared for 1, 2, 7, 7, and X weeks, respectively, in five of the 10 patients without treatment. MRSA persisted in the other five cases. Although all MRSA isolat es found in the initial surveillance culture were susceptible to fusidic ac id (MIC less than or equal to 2 mu g/mL), seven isolates from two patients after fusidic acid treatment demonstrated high fusidic acid resistance (MIC 64 to greater than or equal to 256 mL). Pulsed-field gel electrophoresis p attern analysis showed that the resistant strains were genetically identica l to the susceptible strains isolated from the same patient before fusidic acid treatment, in both cases. However, genetically distinct strains coloni zed in the same individual during follow-up were found in four out of 16 ca ses. We conclude that oral fusidic acid alone is not suitable for eradicati on of MRSA colonization, and may lead to the emergence of resistant strains . (C) 2000 Elsevier Science inc. All rights reserved.