Common coinfections of Giardia intestinalis and Helicobacter pylori in non-symptomatic Ugandan children

Abstract

Background: The protozoan parasite Giardia intestinalis and the pathogenic bacterium Helicobacter pylori are well known for their high prevalences in human hosts worldwide. The prevalence of both organisms is known to peak in densely populated, low resource settings and children are infected early in life. Different Giardia genotypes/assemblages have been associated with different symptoms and H. pylori with induction of cancer. Despite this, not much data are available from sub-Saharan Africa with regards to the prevalence of different G. intestinalis assemblages and their potential association with H. pylori infections.

Methodology/principal findings: Fecal samples from 427 apparently healthy children, 0-12 years of age, living in urban Kampala, Uganda were analyzed for the presence of H. pylori and G. intestinalis. G. intestinalis was found in 86 (20.1%) out of the children and children age 1<5 years had the highest rates of colonization. H. pylori was found in 189 (44.3%) out of the 427 children and there was a 3-fold higher risk of concomitant G. intestinalis and H. pylori infections compared to non-concomitant G. intestinalis infection, OR = 2.9 (1.7-4.8). No significant association was found in the studied population with regard to the presence of Giardia and gender, type of toilet, source of drinking water or type of housing. A panel of 45 G. intestinalis positive samples was further analyzed using multi-locus genotyping (MLG) on three loci, combined with assemblage-specific analyses. Giardia MLG analysis yielded a total of five assemblage AII, 25 assemblage B, and four mixed assemblage infections. The assemblage B isolates were highly genetically variable but no significant association was found between Giardia assemblage type and H. pylori infection.

Conclusions/significance: This study shows that Giardia assemblage B dominates in children in Kampala, Uganda and that the presence of H. pylori is an associated risk factor for G. intestinalis infection.

Figure 1. Incidence of G. intestinalis and H. pylori infections in children of different ages.

Figure 2. Nucleotide maximum likelihood trees based on bg, gdh, and tpi gene sequences from assemblage B isolates.

Unambiguous sequences identified in this study were combined with isolates from our previous studies , . Phylogenetic trees of (A) bg, (B) gdh, and (C) tpi gene sequences. Sequences from this study are indicated in red. Only bootstrap support values >50% are shown.

Figure 3. Nucleotide maximum likelihood tree of the Chromosome 3 locus from the assemblage A isolates.

Phylogenetic relationship of the sequences listed in Supplementary Table S3. Dotted line indicates the branching position of three sequences with a very short branch length. Sequences in red and black differ by four SNPs in the chromosome 5 locus (Supplementary Table S4).