Fusidic Acid Resistance Determinants in Methicillin-Resistant Staphylococcus aureus Isolated in Kuwait Hospitals

Abstract

<b><i>Objective:</i></b> The aim of this study was to investigate the genetic determinants of fusidic acid (FA) resistance in MRSA isolated from patients in Kuwait hospitals. <b><i>Methods:</i></b> The minimum inhibitory concentration (MIC) of FA was tested with <i>E</i>-test strips. Genetic determinants of FA were determined by PCR and DNA microarray. Staphylococcal protein A gene (<i>spa</i>) typing and DNA microarray analysis were used to study their genetic backgrounds. <b><i>Results:</i></b> The FA MIC ranged from 2 mg/L to &#x3e;256 mg/L. Of the 97 isolates, 79 (81.4%) harbored <i>fusC</i>, 14 isolates harbored <i>fusA</i> mutations (<i>fusA</i>), and 4 isolates harbored <i>fusB.</i> Isolates with <i>fusA</i> mutations expressed high FA MIC (MIC &#x3e;256 mg/L), whereas those with <i>fusC</i> and <i>fusB</i> expressed low FA MIC (MIC 2–16 mg/L). The isolates belonged to 23 <i>spa</i> types and 12 clonal complexes (CCs). The major <i>spa</i> types were t688 (<i>n</i> = 25), t311 (<i>n</i> = 14), t860 (<i>n</i> = 8), and t127 (<i>n</i> = 6) which constituted 54.6% of the isolates. The 12 CCs were CC1, CC5, CC8, CC15, CC22, CC80, CC88, and CC97 with CC5 (45.6%) and CC97 (13.2%) as the dominant CCs. <b><i>Conclusions:</i></b> The MRSA isolates belonged to diverse genetic backgrounds with the majority carrying the <i>fusC</i> resistance determinants. The high prevalence of FA resistance belonging to diverse genetic backgrounds warrants a review of FA usage in the country to preserve its therapeutic benefits.