To ascertain the incidence of Acanthamoeba keratitis and the coexistence of Acanthamoeba and fungi in microbial keratitis.

Prospective cross-sectional study.

Patients presenting with stromal keratitis were additionally tested for Acanthamoeba irrespective of the clinical diagnosis. Culture positivity was the gold standard.

Of the 401 cases included in the study, 40 were positive for Acanthamoeba (10%); of these 40, 16 were positive for both Acanthamoeba and fungi (4.5% of the study group was Acanthamoeba and fungal keratitis positive); 5 were positive for Acanthamoeba and bacteria; and 2 had triple infection with Acanthamoeba, fungi, and bacteria. Ring infiltrates and stromal edema are frequently associated with Acanthamoeba keratitis, as well as in Acanthamoeba coinfections. Ring infiltrates in particular were more frequently seen in the Acanthamoeba and fungal keratitis group (8/16) and they were often yellowish with hyphate edges (vs ring infiltrates only, which are seen in the patients with Acanthamoeba alone). Only 2 patients were contact lens wearers: however, they presented with history of trauma.

Acanthamoeba coinfections are much more frequent and are not restricted to contact lens users. Anticipating coinfections is necessary for establishing a diagnosis as well as for appropriate and timely therapeutic interventions.