Comparison of gdh polymerase chain reaction-restriction fragment length polymorphism and tpi assemblage-specific primers for characterization of Giardia intestinalis in children.

Background: Giardia is a diarrheagenic eukaryotic parasite that consists of at least eight morphologically identical but genetically distinct genotypes. Human giardiasis is caused mainly by A and B assemblages.

Aim and objectives: The study aimed to compare the performance of gdh polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and tpi assemblage-specific primers in genotyping of G. intestinalis.

Materials and methods: Stool samples of 315 children were microscopically screened for G. intestinalis. Positive samples were genotyped using tpi assemblage-specific primers and gdh semi-nested PCR-RFLP techniques.

Results: The prevalence of Giardia was 18.1%. The detected genotypes using tpi and gdh approaches were assemblage A (15.8% vs. 12.7%) and assemblage B (36.8% vs. 74.5%) as single infections and mixed assemblages A and B (47.4% vs. 12.7%). The two approaches showed a moderate agreement (kappa index = 0.413, P < 0.001). PCR-RFLP of gdh gene revealed that sub-assemblages BIII and BIV were equally detected (30.9% each). The remaining samples were equally divided between sub-assemblage AII, mixed BIII and BIV, and mixed AII and BIII (12.7% each). A significant association was detected between the retrieved sub-assemblages and the presence of symptoms.

Conclusions: Although both approaches confirmed the predominance of assemblage B, the use of assemblage-specific primers is more effective in elucidating the true picture of mixed assemblage infection.