The Dissemination of Fusidic Acid Resistance Among Staphylococcus epidermidis Clinical Isolates in Wenzhou, China

PURPOSE: Fusidic acid (FA), a potent steroidal antibiotic, is used topically to treat skin and soft tissue infections (SSTIs) caused by Staphylococci. The aim of this study is to report the prevalence of fusidic acid resistance among Staphylococcus epidermidis clinical isolates from a tertiary hospital in Wenzhou, east China. METHODS: The antibiotic susceptibility of S. epidermidis isolates was determined by disc diffusion method and agar dilution method. Then, FA-resistant S. epidermidis isolates were characterized by multi-locus sequence typing, SCCmec typing and pulsed-field gel electrophoresis. RESULTS: In the present study, the 55 (7.7%) FA-resistant S. epidermidis among 711 S. epidermidis clinical isolates were isolated from different parts of 53 patients. Fifty-five FA-resistant S. epidermidis isolates with FA MIC values ranged from 4 to 32 μg/mL. Among them, 50 (90.9%) were identified as methicillin-resistant Staphylococcus epidermidis (MRSE), in which mecA were positive. Meanwhile, the positive rates of fusB and fusC genes among FA-resistant S. epidermidis isolates were 85.5% (47/55) and 7.3% (4/55), respectively. All 55 isolates mentioned above were susceptible to vancomycin. More than 50% of FA-resistant isolates were resistant to non-β-lactam antimicrobials including erythromycin (80.0%, 44/55), clindamycin (65.5%, 36/55), ciprofloxacin (63.6%, 35/55) and sulfamethoxazole (63.6%, 35/55). A total of 14 sequence types (STs) were identified among the 55 FA-resistant S. epidermidis isolates, of which, ST2 (24/55, 43.6%) was the most predominant type. And the eBURST analysis showed that CC2, CC5 and CC247 accounted for 43.6% (24/55), 27.3% (15/55) and 14.5% (5/55), respectively. Meanwhile, a total of four SCCmec types (I, III, IV, V) were identified among the 55 FA-resistant S. epidermidis. Furthermore, the pulsed field gel electrophoresis divided the 55 isolates into 20 types, namely A-T. Q-type strains were most prevalent, accounting for 30.9% (17/55). CONCLUSION: Taken together, the dissemination of S. epidermidis ST2 clone with FA resistance can cause trouble in controlling S. epidermidis infections.