The antibiotic resistance profiles of Staphylococcus in the Asia Cornea Society infectious keratitis study

Abstract

Purpose: To investigate the antibiotic susceptibility profiles of Staphylococcus species, specifically S. aureus and S. epidermidis, collected from the Asia Cornea Society Infectious Keratitis Study (ACSIKS). Methods: Isolates were re-identified in this laboratory study, and antibiotic susceptibility was determined by broth microdilution. A panel of 11 antibiotics from 7 classes were tested. The minimum inhibitory concentration was determined based on Clinical Laboratory Standard Institute guidelines, where available. Isolates were classified as susceptible, intermediate, or resistant, with methicillin-resistance determined by oxacillin susceptibility. Multidrug resistance (MDR) was defined as resistance to at least one agent in three or more antimicrobial categories. Results: A total of 490 staphylococci isolates were analyzed, with S. epidermidis (42%) and S. aureus (24.1%) the most prevalent. Vancomycin was universally effective against both species. However, resistance to the common fluoroquinolones was high in S. aureus (49.1%–51.6%) and S. epidermidis (36.9%–40.3%). Methicillin-resistance was present in 33.1% of S. aureus and 47.6% of S. epidermidis isolates. MDR was significantly associated with methicillin-resistance, with 85% of methicillin-resistant S. aureus and 66.3% of methicillin-resistant S. epidermidis exhibiting MDR. Conclusion: Antibiotic resistance is common in Staphylococcus species causing infectious keratitis in Asia. High rates of resistance to the commonly used fluoroquinolones and the prevalence of MDR in methicillin-resistant isolates pose a major challenge. The findings emphasize the need for local data to guide treatment decisions and to consider alternative antibiotics in cases with multidrug resistance.