A longitudinal study of trends in keratitis in Australia

To analyze the changes in risk factors, corneal culture results, antibiotic resistance, treatment, and clinical outcomes of patients with keratitis presenting to a major public hospital in Australia over a 5-year period.

A retrospective audit of all patients who had a corneal scraping between October 1999 and September 2004 at the Princess Alexandra Hospital. Clinical information was gathered from medical records and smear and culture results from the local microbiology database. The trends over time in patient demographics, keratitis risk factors, corneal culture results, antibiotic resistance, treatment, and clinical outcomes were analyzed by using linear regression. By using a moving average, we analyzed differences in the rate of culture of each causative organism for each month of the year with linear regression from the month of highest presentation. The mean of maximum temperatures on the days of presentation between different groups of organisms was compared.

The proportion of patients presenting with keratitis related to contact lens wear increased significantly (12%-29%; P = 0.04) and with keratitis related to ocular surgery decreased significantly (18%-8%; P = 0.009) through the study. Antibiotic resistance of cultured bacteria to cephalothin increased significantly (2%-12%; P = 0.02), whereas resistance to ciprofloxacin and gentamicin remained at a low level throughout the study. There was significant variation in the monthly recovery of Pseudomonas aeruginosa (P = 0.04) and fungi (P = 0.02), which were cultured more frequently in summer months, whereas Streptococcus pneumoniae (P = 0.04) was more common in winter months than in other times of the year. Treatment with fluoroquinolones increased significantly (14%-40%; P = 0.002) through the study, and the rate of good outcomes also increased significantly (42%-72%; P = 0.02).

In this series, keratitis related to contact lens wear became more frequent, whereas keratitis related to prior ocular surgery became less frequent. Different organism groups showed significant seasonal variations in their presentation, and bacterial resistance to cephalothin increased significantly.