A Case-Control Study of Detection of the Potentially Pathogenic <i>Acanthamoeba</i> Strains From the Oral Cavity of Diabetic Patients, Cancer Patients, and Healthy Individuals in Iran

Background and aims: Acanthamoeba is a genus of free-living amoebae (FLA) that can cause granulomatous amoebic encephalitis and amoebic keratitis. This study aimed to identify Acanthamoeba strains among diabetic and cancer patients and healthy individuals. Methods: In this cross-sectional study, 324 sterile cotton swab samples were collected from the oral cavity of 108 diabetic patients, 106 cancer patients undergoing chemotherapy, and 110 healthy individuals from June to October 2018 in Shahrekord, Iran. Samples were cultured onto 1.5% non-nutrient agar, and the Acanthamoeba spp. were investigated with morphological, molecular (polymerase chain reaction targeting 18SrRNA), and pathogenicity assays. Results: FLA was found in 130/324 (40.1%) oral cavity samples of individuals. Microscopic results using Giemsa staining revealed that 14/37 (37.8%) and 31/93 (33.3%) FLA isolated from healthy individuals and immunocompromised patients were identified as Acanthamoeba spp. Moreover, the PCR confirmed the existence of Acanthamoeba spp. in 4.7% of patients and 3.6% of controls. In addition, the PCR demonstrated that Acanthamoeba spp. were isolated in 6.6%, 8.2%, and 6.3% of cancer patients, diabetic patients, and healthy individuals, respectively. According to the sequence analysis of PCR products of 18S rRNA, the T4 (10 isolates) and T5 (3 isolates) genotypes of Acanthamoeba were identified in two groups. Finally, nine isolates genotyped as T4 were positive for potential pathogenic assays. Conclusion: The presence of the potentially pathogenic Acanthamoeba T4 genotype in both immunocompromised patients and healthy individuals indicated that it may pose a risk factor for immunocompromised individuals.