Spectrum of Microbial Keratitis Encountered in the Tropics

PURPOSE: To report the predisposing factors, microorganisms, antibiotic sensitivity associated with bacterial keratitis, and treatment outcomes in Miri, Borneo which has a tropical climate.

METHODS: This is a retrospective study on patients presenting with microbial keratitis in Miri, Sarawak, Borneo over a 7-year period from January 1, 2010 until December 31, 2016. Demographic data, predisposing factors, culture and sensitivity results together with treatment outcomes were studied.

RESULTS: There were a total of 221 cases treated as microbial keratitis with a peak age group of 21 to 30 years. The predisposing factors were trauma (49.3%), improper contact lens usage (29.1%), ocular surface diseases (5.9%), ocular surgeries (0.9%), drugs (1.8%), and other factors (19.0%). Occupational injuries among oil palm plantation workers was the leading cause within the trauma cohort (28.8%). Corneal scraping was performed in 189 cases, 61.4% of them yielded positive cultures. The cultures demonstrated that 49.1% were of bacterial origin, 46.6% were fungal, and 4.3% showed mixed growth. The most common bacteria isolated was Pseudomonas aeruginosa, which was sensitive toward ceftazidime and gentamicin antibiotics. One hundred ninety-two cases (86.9%) were treated with purely topical medication, whereas 29 cases (13.1%) required further interventions.

CONCLUSION: The commonest predisposing factor for microbial keratitis was trauma. With the nearby oil palm industries, we report a corresponding increase of incidence in fungal keratitis at our center. Culture and sensitivity reports from corneal scrapings are essential in treatment guidance; however, more than a third of the microbial keratitis cases studied were culture-negative. The organisms cultured reflect the profile expected in tropical climates. Fortunately, there was no increase in resistance rates observed for the commonly used antibiotics.