Background: Genotypic variation of H. pylori is associated with the existence of virulence factors, while
different genotypes and subtypes of Cryptosporidium spp. are responsible for human cryptosporidiosis.
Objective: To investigate usefulness of multilocus sequence typing (MLST) to analyze the genetic diversity
of H. pylori and Cryptosporidium spp. co-infections in diarrheic immunocompetent Egyptian children. The
secondary objective is to determine the detection rate of each pathogen, and co-infection rate, as well as
its associated factors.
Subjects and Methods: This cross-sectional study included 305 immunocompetent diarrheic children.
Faecal samples were collected and processed using molecular screening techniques to detect and
differentiate Cryptosporidium spp. and H. pylori. Cryptosporidium spp. were genotyped by amplifying the
18S rRNA gene, and the gene encoding Cryptosporidium oocyst wall protein (COWP) using nested PCR
followed by restriction fragment length polymorphism (RFLP). Whereas H. pylori strains were identified
using PCR to detect genes encoding UreA and CagA. The study also analyzed sociodemographic and clinical
parameters to determine associated factors with Cryptosporidium-H. pylori co-infection.
Results: Out of the whole studied population, 12.1% had Cryptosporidium spp., predominantly C. hominis
(81.1%); while H. pylori DNA was found in 41.0%, with predominance of the CagA+ strain (40.8%). Among
the 37 Cryptosporidium-positive cases, 27 (73%) had a co-infection with H. pylori, and 14 (51.9%) were
identified with CagA+ strain. Significant associations were recorded between cryptosporidiosis and factors
such as age, gender, source of water and milk, and abdominal pain, while H. pylori infection correlated
significantly with age, vomiting, and abdominal pain. Co-infections were associated with vomiting and
fever, particularly noting that CagA+ H. pylori strain significantly correlated with more severe symptoms,
indicating its higher pathogenic potential.
Conclusion: This study accepted the complex interplay between H. pylori and Cryptosporidium spp.
in immunocompetent children in Egypt, emphasizing the role of genetic diversity and strain-specific
virulence in disease manifestation.