Sir,

Acanthamoeba keratitis (AK) is a rare infection that is estimated to occur in between 1–100 cases per million contact lens wearers per year, suggesting that the simple probability of re-infection is low.1, 2 Although recrudescence has been reported, we report a patient with two genotypically, geographically and temporally distinct AK infections.

Case report

A 16-year-old male soft contact lens wearer (phemfilcon) using an unspecifed Renu branded solution and AMO Complete MoisturePlus (AMO-CMP) presented to the University of Illinois Eye and Ear Infirmary with keratitis refractory to topical and systemic antivirals. Visual acuity of the affected right eye was 20/70. Examination revealed an epitheliitis with radial keratoneuritis. Epithelial debridement was performed, followed by topical propamidine isethionate (Brolene, Sanofi-Aventis, Paris, France) and chlorhexidine gluconate 0.02% hourly, which was tapered over 4 months. The patient was refit with soft contact lenses (lotrafilcon B) using AMO-CMP by another practitioner after clinic discharge.

One year later, he again presented with a 2-week history of severe pain and decreased vision in the same eye without interim symptoms. He reported recently swimming in a lake with his contact lenses, near his new home, 900 miles away. Visual acuity was 20/40, with an anterior stromal keratitis and identical treatment initiated.

Confocal microscopy, smear, and culture were positive at each presentation. The final spectacle corrected vision was 20/20 after each treatment. Sequence analyses indicated genetically distinct isolates with 13/135 base pair differences of the 18S rRNA gene (Figure 1).

Figure 1
figure 1

DNA sequence analyses for isolate identification of the Acanthamoebae from the patient's first keratitis (UIC Presentation 1) and second keratitis after restarting contact lens wear (UIC Presentation 2). Shaded sites indicate locations where the bases differ between UIC Presentation 1 and 2. Empty sites indicate that all sequences are the same as sequence 1, A. sp V125 (Acanthamoeba species V125). UIC Presentation 1 and UIC Presentation 2 each individually resembles previously sequenced isolates A. sp V125 and A. quina, respectively.

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Comment

Recrudescent and bilateral AK are considered to be due to incomplete treatment and contemporaneous environmental exposure, respectively.3 While initial infection involving two or more strains is possible, an asymptomatic interval of greater than a year and isolation of two genetically distinct species suggest unique infections. A cornea compromised by past infection, poor hygiene, and solution use were likely contributing factors.4

Patients are often eager to return to contact lens wear, notwithstanding animal studies suggesting a lack of protection from prior infection and the possibility of differential individual susceptibility.5 Our case illustrates that, despite the rarity of AK, this can manifest in humans and, without any modification in risk factors, AK patients persisting with contact lens wear sustain demonstrable risk for re-infection.