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

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).

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.

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.

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.