Fusidic Acid Resistance in Staphylococcus aureus Strains in an Interval of Ten Years (2001-2011)

Objective: Fusidic acid is a steroid-like antibiotic which is used alone or consecutively in combination with other antimicrobial drugs in the treatment of staphylococcal infections, including the strains resistant to methicillin. In this study, we aimed to compare fusidic acid resistance rates in Staphylococcus aureus [methicillin susceptible Staphylococcus aureus (MSSA) and methicillin resistant Staphylococcus aureus (MRSA)] strains isolated in our hospital's clinical microbiology laboratory at an interval of ten years. Material and Methods: Bacterial strains were identified by conventional methods and BD PhoenixTM Automated Microbiology System (BD Diagnostic Systems, Sparks, MD). Methicillin and fusidic acid susceptibilities of the identified S. aureus strains were determined according to Clinical and Laboratory Standards Institute (CLSI) criteria. In order to determine methicillin and fusidic acid susceptibilities, 1 mu g oxacillin and 10 mu g fusidic acid disks (Oxoid Ltd., Basingstoke, United Kingdom) were used. Oxacillin susceptibility was detected according to the criteria of CLSI, and inhibition zone of >= 13 mm was considered as sensitive, 11-12 mm as intermediate, <= 10 mm as resistant. Fusidic acid susceptibility was detected according to the criteria of Comite de L'antibiogramme de la Societe Francaise de Microbiologie, and inhibition zone of 22 mm was considered as sensitive, 16-21 mm as intermediate, <= 15 mm as resistant. Results: In a study carried out ten years ago, fusidic acid resistance rate in S. aureus strains was reported as 11.6%, whereas in our study it was found as 14.6%. There was not any significant difference between the two resistance rates (p=0.695). Fusidic acid resistance rates were found to be 4.2% and 5.7%, respectively in the years 2001 and 2011 for MSSA strains. In MRSA strains, however, the rates were found as 18.9% and 22.2%, respectively. No significant difference was noted between fusidic acid resistances of MSSA and MASA strains, studied at the two different periods (p=1.00, p=0.906). Conclusion: In the light of these findings, it has been concluded that fusidic acid is still a good alternative drug in the treatment of all staphylococcal infections, including methicillin resistant strains.