Isolation of Acanthamoeba genotype T4 from a non-contact lens wearer from the Philippines

Abstract

We report a case of a 76-year old Filipino male from the province of Porac, Pampanga who presented with pain, redness, and blurring of vision of the right eye (oculus dexter, OD) on 25 February 2009. One and a half weeks prior to consultation, patient complained of right eye discharge and lid swelling. The patient consulted an ophthalmologist and was given unrecalled topical eye medications. There was no improvement from the symptoms and patient complained of worsening pain and redness in the right eye. The patient was a non-contact lens wearer and he denied any trauma to the right eye. However, he admitted to washing both eyes with tap water. Visual acuity in the right eye was counting fingers at 3 feet. Slit lamp examination showed diffuse conjunctival injection. There was note of a ring-like infiltrate in the cornea almost extending to the limbus. There was also note of significant anterior chamber cells reaction and hypopyon. Primary working impression was Acanthamoeba keratitis (AK), OD. Corneal scraping was done and sent to the St. Luke's Research and Biotechnology for detection and identification of the infectious agent. Morphological detection was done by allowing the organism from the scraping to grow in 1.5% non-nutrient agar plate with heat-killed E. coli. Trophozoites with acanthopodia and double-walled cysts characteristic of Acanthamoeba were observed within the first and second week of observations, respectively. Molecular identification of the amoebae at the genus level based on the presence of Acanthamoeba-specific amplimer S1, ASA. S1 (a partial 18S ribosomal DNA gene) confirmed the morphological identification (band at 461-bp). Genotyping through sequence revealed that the organism belonged to T4, which is the genotype commonly present from the eye of keratitis patients.