Abstract
Purpose To investigate microbiological and clinical characteristics of recurrent S. aureus keratitis.
Methods Patients with S. aureus keratitis were included. For a subgroup, samples were collected from affected and unaffected corneas and contiguous sites (conjunctiva, lids, nose) at presentation and on days 3, 7 and 28. Samples were cultured, amplified and analysed using metagenomics (Illumina and Nanopore sequencing followed by hybrid assembly and annotation). Comparisons were undertaken of clonal type and presence of virulence genes in S. aureus between patients with and without recurrent disease. Patients were grouped according to presence of risk factors: group 1 (contact lens), group 2 (corneal disease), group 3 (systemic disease), group 4 (ocular surface disease) and group 5 (previous keratitis).
Results Twenty-five patients with recurrent disease and 60 without were included (age 69.20 SD 14.50). Mean healing time was 25.55 days (SD 14.74) and ulcer size 1.99 x 1.31 mm. There was no difference in clonal type, but 3 virulence genes (p=0.03, p=0.01 and p=0.009) were significantly more likely to be present in S. aureus from patients with recurrent disease. Bar one patient with recurrent disease, the same strain of S. aureus isolated from cornea at initial and recurrent episodes. S. aureus persisted at contiguous sites in both recurrent and non-recurrent disease and was isolated more frequently from conjunctiva and nose compared to controls (p=0.03).
Conclusions Treatment of S. aureus keratitis only with topical antimicrobials is insufficient to remove S. aureus from contiguous sites and patients remain at risk of further keratitis.
