Risk for culture positive bacterial keratitis (BK) is elevated among individuals who either wear contact lenses, have an ocular surface disease  or have systemic immunosuppression, according to a retrospective study published in Frontiers in Medicine.

Researchers from University of Nottingham sourced data from the Queen’s Medical Center in the United Kingdom. Patients (N=283) who had suspected BK between 2015 and 2019 were assessed for bacterial cultures, comorbidities, treatments, and visual outcomes.

Patients had a  mean age of 54.4±21.0 years, 50.9% were men, and 96.5% had  at least 1 risk factor for BK.


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The most frequently observed risk factor was ocular surface diseases (47.3%). The investigators also noted additional risk factors such as contact lens wear (35.3%), and systemic immunosuppression (18.4%). Stratified by age, older patients (>50 years) were more likely to have systemic immunosuppression (P <.001) and younger patients were more likely to wear contact lenses (P <.001).

Bacterial cultures were positive for 45.2% and 7.8% of positive cases had ≥2 causative bacteria. The most frequently observed causative organisms included Pseudomonas (31.9%) and Staphylococci (26.1%). Stratified by risk factors, patients who wore contact lenses were less likely to be positive for Gram-positive bacteria compared with other risk groups (P =.017).

Compared with negative cultures, positive BK was associated with poorer corrected-distance-visual-acuity (CDVA; P <.001), large epithelial defect or infiltrate (P <.001), hypopyon (P <.001), admission to the hospital (P <.001), central or paracentral ulcer (P =.002), older age (P =.004), use of topical corticosteroids (P =.008), and prior corneal surgery (P =.011).

Most eyes (83.7%) were successfully treated medicinally and 16.3% required surgical intervention. Complete corneal healing was achieved by 98.2% (n=278).

Following BK treatment, CDVA improved from 1.17±1.03 to 0.80±1.00 logMAR (P <.001). Poor visual outcomes (CDVA <0.6 logMAR) associated with baseline CDVA <0.6 logMAR (odds ratio [OR], 29.70; 95% CI, 10.47-84.18; P <.001), infiltrate size >3 mm (OR, 4.07; 95% CI, 1.21-13.73; P =.024), age >50 years (OR, 2.61; 95% CI, 1.24-5.47; P =.011), and central ulcer (OR, 2.13; 95% CI, 1.01-4.51; P =.047).

The investigators reported adverse events of raised intraocular pressure (11.3%), infection recurrence (9.9%), corneal perforation (8.8%), vision loss (3.9%), eye loss (1.4%), and phthisis bulbi (0.4%).

This study may have been biased by including both culture negative and culture positive cases in their analyses.

Although most patients were treated successfully, patients who were older, those who had poor vision at baseline, and patients with more aggressive forms of BK were at increased risk for poor visual outcomes.

Reference

Ting DSJ, Cairns J, Gopal BP, et al. Risk factors, clinical outcomes, and prognostic factors of bacterial keratitis: The Nottingham Infectious Keratitis Study. Front. Med. Published online August 11, 2021. doi:10.3389/fmed.2021.715118