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Abstract
AIMS
1. To establish the patient demographics, risk factors, causative organisms, levels of antibiotic resistance, clinical presentations and treatment patterns of keratitis at a tertiary referral hospital in Australia.
2. To establish any change in these factors over 5 years.
3. Establish the factors associated with poor outcomes.
METHODS: A retrospective audit of all patients who had a corneal culture in 5 years was conducted. Patients' clinical information was gathered from medical records and smear, culture and antibiotic resistance results were gathered from the local microbiology database. Associations between risk factors for keratitis and patient variables were analysed statistically. Outcome of a patient's episode of keratitis was classified as poor using final criteria. Trends over time in variables were analysed using linear regression.
RESULTS: Two hundred and fifty-three (253) corneal cultures of 231 patients were included. Sixty percent (60%) of patients were male and there was a bimodal distribution in the age of presentation. Common risk factors for keratitis were contact lens wear (22%), ocular surface disease (18%), ocular trauma (16%) and prior ocular surgery (11 %). Corneal cultures were positive in 65% of cases and Pseudomonas aeruginosa (27%), coagulase-negative staphylococci (13%), Staphylococcus aureus (12%) and fungi (7%) were recovered. There was significant variation in the monthly recovery of P. aeruginosa (p=0.04) and fungi (p=0.02) which were more frequent in summer months, while Streptococcus pneumonia (p=0.04) was more common in winter months. Antibiotic resistance of cultured bacteria to cephalothin increased significantly (2% to 12%; p=0.02). Final vision of 6/12 or better was found in 48% (100) of cases while a poor outcome was seen in 28% (58) of cases. Multivariate analysis showed that the relative risk of a patient having a poor outcome was 4.3x (confidence interval [Cl] 2.0 to 9.5) if they had severe keratitis, 4.1 x (Cl 1.8 to 9.5) if they had keratitis related to ocular surface disease and 3.8x (Cl 1.8 to 8.3) if they were over 50 years old.
CONCLUSIONS
1. In this series the most common risk factor for keratitis was contact lens wear and the most commonly isolated organism was P. aeruginosa which had seasonal variation in rate of recovery.
2. Keratitis related to contact lens wear became more frequent while keratitis related to prior ocular surgery became less frequent.
3. A poor outcome is more likely in patients with severe keratitis, keratitis related to prior ocular surface disease or older age.