Microbial Keratitis in Southern Arizona

There is a paucity of data on microbial keratitis in the southwestern USA, specifically southern Arizona. Understanding demographic factors and causative organisms will help design future treatments and preventative measures.

A retrospective chart review was conducted on all cases (>17 years old) of microbial keratitis at Banner University Medical Center Tucson, Arizona, from September 1, 2017, to August 31, 2022. Frequencies of social, demographic, ocular factors, and isolated organisms were reported. We used Fisher's exact tests to compare findings with 2023 census data.

We identified 272 eyes in 268 patients. Compared with census data, demographic factors overrepresented in microbial keratitis were as follows: unemployment (50.4%) and homelessness (8.2%). Drug use was identified in 22.4% of patients. Associated factors were contact lens wear (33.1%) and preceding ocular trauma (14.7%). Among eyes associated with contact lens use, 49 (54.4%) were worn overnight. Of 203 eyes with culture results, 152 (74.9%) yielded a positive microbial culture; 96.5% were bacterial and 3.4% were fungal. Gram-positive bacteria were found in 54.7%, most commonly Staphylococcus epidermidis (16.7%). The most common gram-negative isolate was Pseudomonas aeruginosa (12.8%).

In southern Arizona, microbial keratitis is particularly associated with drug use, unemployment, and homelessness. Contact lens use and overnight wear were common, warranting education on safe practices. Positive fungal cultures were rare. Each factor deserves consideration for societal intervention, to reduce the burden of microbial keratitis in southern Arizona, and should be evaluated as potential risk factors in other communities. Overall culture results may influence choice of initial therapy.