Genotyping of Giardia duodenalis cysts by new real-time PCR assays for detection of mixed infections in human samples

Genotypes of Giardia intestinalis clinical isolates of gastrointestinal symptomatic and asymptomatic Saudi children

Giardiasis is the most worldwide parasitic disease with the major clinical impact on infant and children. Two genotypes were reported commonly among humans (assemblage A and B). In this study, genotypes of Giardia intestinalis clinical isolates obtaining from 24 gastrointestinal symptomatic Saudi primary school children and 16 asymptomatic ones were explored by real-time polymerase chain reaction using the high resolution melting curve analysis targeting intergenic spacer (IGS) region rDNA of G. intestinalis. Children having acute, intermittent, and chronic diarrhea were 14, 5, and 5, respectively. Among all the giardiasis subjects, assemblage B was 37.5% followed by both of assemblages AI and AII with 30% and 27.5%, respectively. Mixed infection with the three previous assemblages was present in 5% of cases. Among symptomatic children, the prevalence of assemblage B was 62.5% then followed by assemblage AI (16.7%) and assemblage AII with 12.5%. All of the children who harbored G. intestinalis assemblages B were symptomatic, while asymptomatic ones had only assemblage AI and AII with 50% each. The difference was statistically highly significant. In symptomatic patients having acute diarrhea, assemblage B was present in 71.5%, while assemblage AI and AII were equal with 7.1%. All of the patients (14.3%) with mixed infection had acute diarrhea. In intermittent diarrhea, assemblage AI and B were equally distributed with 40% each. In chronic diarrhea, assemblage AI and AII were equal with 20% each, while assemblage B was found in 60%. The difference was statistically not significant. In conclusion, assemblage B is the commonest, while assemblage A is a predominant in symptomatic and asymptomatic giardiasis Saudi children, respectively. So human transmission is the common risk factor among symptomatic, while zoonotic transmission is a common risk factor in asymptomatic ones. On the other hand, a strong correlation between assemblage B and symptoms and no relation between genotypes and types of diarrhea are found. Also, PCR with HRM in one-step closed-tube methods is able to genotype G. intestinalis IGS rDNA without using the sequencing methods or the electrophoresis.