Acanthamoeba often goes hand-in-hand with other ocular infections, and these co-conditions aren’t just limited to contact lens wear, a study in the American Journal of Ophthalmology reports.

In an effort to find the incidence of Acanthamoeba keratitis and the coexistence of Acanthamoeba and fungi in microbial keratitis, researchers from India conducted a prospective cross-sectional study in which they tested for Acanthamoeba in patients who presented with stromal keratitis.

Out of 401 cases, the study found 40 patients—or 10%—were positive for Acanthamoeba, and 16 of the 40 tested positive for both Acanthamoeba and fungi (4.5%). Additionally, five out of the 40 subjects tested positive for Acanthamoeba and bacteria and two out of the 40 had a triple infection consisting of Acanthamoeba, fungi and bacteria.

Researchers also looked for ring infiltrates and stromal edema, since both are frequently associated with Acanthamoeba keratitis and Acanthamoeba coinfections. Investigators found ring infiltrates were more frequent in the Acanthamoeba keratitis-fungal keratitis group (eight out of 16). Additionally, they were often yellowish with hyphate edges vs. ring infiltrates only, which were seen in patients with AK alone.

Of note, only two patients were contact lens wearers, and these subjects presented with a history of trauma.

Acanthamoeba coinfections “are much more frequent and not restricted to contact lens users,” the researchers noted in their paper. “Anticipating coinfections is necessary both for establishing a diagnosis as well as for appropriate and timely therapeutic interventions,” they concluded.

Raghavan A, Baidwal S, Venkatapathy N, et al. The Acanthamoeba-fungal keratitis study. Am J Ophthalmol. February 2, 2019 [Epub ahead of print].