Serratia marcescens keratitis after photorefractive keratectomy

Clinico-microbiological Features and Treatment Outcomes of Serratia Keratitis and Comparison with Pseudomonas aeruginosa Keratitis

PURPOSE

To describe clinico-microbiological features and outcomes of Serratia keratitis and to compare them with Pseudomonas aeruginosa keratitis.

METHODS

Cases of microbiologically proven Serratia keratitis and P. aeruginosa keratitis were reviewed. Data regarding demographic and clinical characteristics, and outcomes were recorded.

RESULTS

39 patients with pure Serratia keratitis were included. Median presenting vision was 1.8 logMAR (IQR, 0.8-2.4) and median infiltrate size was 5 mm (IQR 3-7.8 mm). An ocular risk factor was present in 35 (89.7%) cases. S. marcescens was the most common species (31/39, 79.5%). Medical resolution was observed in 36/39 (92.3%) cases, while three (7.7%) eyes needed penetrating keratoplasty. On comparing with P. aeruginosa keratitis (58 eyes), no difference in outcomes (p = .14) was noted.

CONCLUSION

Serratia keratitis usually occurs in eyes with a compromised surface and has good resolution with medical therapy. Both Serratia and P. aeruginosa keratitis have similar outcomes.

Microbial keratitis after corneal laser refractive surgery

Corneal laser refractive surgery is increasingly being performed on patients with the aim of improving unaided vision. Most candidates for surgery have excellent spectacle- or contact lens-corrected vision. Although microbial keratitis following refractive surgery is a rare complication, and usually has a good visual outcome, it can be sight-threatening. The spectrum of pathogens differs to other causes of microbial keratitis, such as contact lens-associated keratitis, and a different management approach is required. Postoperatively, patients are prescribed topical steroids and broad-spectrum topical antibiotics, typically fluoroquinolones. These do not cover unusual organisms, such as fungi, Nocardia, Acanthamoeba and some atypical mycobacteria. In post-laser-assisted in situ keratomileusis microbial keratitis, the lamellar flap should be lifted to acquire samples for specific microbiological examination, including these atypical organisms. Confocal microscopy is a noninvasive test that provides morphological information, and is operator dependent, but may assist in the rapid diagnosis of fungal, Acanthamoeba or Norcardia keratitis. PCR is not in widespread use, but has high sensitivity and specificity, and may facilitate early diagnosis and specific treatment of the causative organism, which is critical in obtaining the best clinical outcome.