Comparison Between Different Methods for Diagnosis of Acanthamoeba Infection and Isolation of Genotype T9 From a Contact Lens Cases

Abstract

Acanthamoeba genus is a medically important free living amoeba causing serious humans infections. Amoebic keratitis (AK) is a sight threatening infection of cornea caused by Acanthamoeba pathogenic genotypes, which prevalence remarkably increased in developed countries. The study compared different methods for diagnosing AK and identified Acanthamoeba genotypes by molecular examination in contact lens wearers (CLWs). Patients were 79 clinical corneal swaps (CS) and 15 samples from contact lens storage cases (CLSC). Clinical CSs were divided into four groups; GI: 20 patients suffering from chronic corneal ulcers, GII: 15 patients with traumatic ulcers, GIII: 24symptomatic CLWs and GIV: 20asymptomatic control individuals. CLSC were provided from apparently healthy asymptomatic CLWs (15). Swabs and solution samples were underwent microscopic and staining examination, cultivation on non-nutrient agar (NNA) plates and PCR molecular analysis. Sequencing and genotyping of PCR-positive samples were performed.The results showed that Acanthamoeba parasites were detected in 3.8% of CS and 6.7% of CLSC samples. The highest significantly positive results were by culture (3.8%) followed by Giemsa and trichrome stains (2.5%) and lastly direct microscopy (1.3%) of CS samples. Only one positive sample (6.7%) was detected in CLSC by all methods, but without statistical significance. Sensitivity of PCR compared to culture was 25%.Acanthamoeba parasites in CS were from subgroup II with 12.5% detection rate in CLWs, but the positive case from CLSC was from subgroup I with 6.7% detection rate. This study confirmed different risk factors in association with AK in CLWs. Genotype determination for Acanthamoeba positive case by PCR revealed homology with Acanthamoeba genotype T9 isolate ICS20.