Abstract
Purpose :
Staphylococcus aureus (SA) is among the most frequent bacterial pathogens recovered from ocular surface infections. Disease progression and immune evasion is impacted by a variety of virulence factors, including surface capsular polysaccharide (CP) type. In the US, the majority of SA isolates are either CP5 or CP8 genotype. We tested the hypothesis that the predominant ocular Staphylococcus aureus capsular genotype would coincide with CP8, typically of community origin.
Methods :
We selected and characterized 201 current and archived SA isolates recovered from four ocular surface niches: cornea (n=93), conjunctiva (n=45), lids (n=33), and lacrimal (n=30) during 2022-2023. Individual PCR schemes were utilized to determine prevalence of CP5 vs CP8 genomic signatures, and presence of the PVL cytotoxin gene. SA isolate ID was confirmed by a combination of colony morphology, beta hemolysis, and coagulase reaction. Fluoroquinolone and methicillin resistance were determined using the Vitek-2 system. We evaluated the ability of MSSA (n=7) and MRSA (n=9) to grow among PBS, TSB, and serum tears liquid media.
Results :
CP genotypes were documented for 93.0% (187/201) of isolates with the remaining 14 (7%) documented as non-typeable. CP5 constituted 62% (116/187) of typable isolates vs 38% (71/187) for CP8. Niche prevalence for CP5 included cornea at 49.1%, conjunctiva at 22.4%, lacrimal at 16.4% and lids at 12.1%. Niche distribution for CP8 included cornea at 39.4%, conjunctiva at 22.5%, lids at 22.5% and lacrimal at 15.5%. PVL positivity-rate was 22.4% (45/201). Fifty (26.9%) of the 186 evaluated isolates were moxifloxacin resistant (26.9%). Methicillin resistance among this group was 38.3% (77/201); predominantly CP5 50.6% (39/77) and most frequently recovered from cornea 37.7% (29/77). Both CP5 and CP8 MSSA and MRSA isolates demonstrated depressed growth in 20% and 50% serum tears.
Conclusions :
CP5, commonly associated with healthcare exposure and antibiotic resistance, was the dominant capsular genotype recovered from ocular surface niches. This was contrary to our hypothesis and has important implications for antibiotic therapy and patient management.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.