CRISPR-like sequences in Helicobacter pylori and application in genotyping

Background: Many bacteria and archaea possess a defense system called clustered regularly interspaced short palindromic repeats (CRISPR) associated proteins (CRISPR-Cas system) against invaders such as phages or plasmids. This system has not been demonstrated in Helicobacter pylori. The numbers of spacer in CRISPR array differ among bacterial strains and can be used as a genetic marker for bacterial typing. Results: A total of 36 H. pylori isolates were collected from patients in three hospitals located in the central (PBH) and southern (SKH) regions of Thailand. It is of interest that CRISPR-like sequences of this bacterium were detected in vlpC encoded for VacA-like protein C. Virulence genes were investigated and the most pathogenic genotype (cagA vacA s1m1) was detected in 17 out of 29 (58.6%) isolates from PBH and 5 out of 7 (71.4%) from SKH. vapD gene was identified in each one isolate from PBH and SKH. CRISPR-like sequences and virulence genes of 20 isolates of H. pylori obtained in this study were analyzed and CRISPR-virulence typing was constructed and compared to profiles obtained by the random amplification of polymorphic DNA (RAPD) technique. The discriminatory power (DI) of CRISPR-virulence typing was not different from RAPD typing. Conclusion: CRISPR-virulence typing in H. pylori is easy and reliable for epidemiology and can be used for inter-laboratory interpretation