Rapid combined characterization of microorganism and host genotypes using a single technology.

BACKGROUND: Genetic information is becoming increasingly important in diagnosis and prognosis of infectious diseases. In this study we investigated the possibility of using a single technology, the Pyrosequencing trade mark technology (Biotage AB, Uppsala, Sweden), to gather several kinds of important genetic information from the human pathogen Helicobacter pylori, as well as from the carrier of the H. pylori infection. MATERIALS AND METHODS: DNA from 87 clinical isolates of H. pylori, 50 isolates from H. pylori-infected transgenic mice and nine gastric biopsies from H. pylori-infected patients was analyzed for targets in the 16S rRNA, 23S rRNA and cytotoxin associated gene A (cagA) genes to determine species identity, clarithromycin susceptibility and virulence level, respectively. In addition, three single nucleotide polymorphisms in the human interleukin-1B (IL-1B) gene, reported to affect the risk of developing gastric cancer, were analyzed in the gastric biopsy samples. RESULTS: All DNA targets were processed and analyzed in parallel, enabling convenient genetic characterization of both pathogen and host. All genotypes were easily and accurately assigned. In the 16S rRNA analysis, 99.83% of the bases were correctly called. CONCLUSIONS: We conclude that genetic analysis using Pyrosequencing trade mark technology was nonlaborious, and gave highly accurate data for different kinds of target. We therefore believe that this technology has the potential to complement or in the future substitute the time-consuming traditional microbial identification and typing methods, as well as enabling rapid typing of relevant host genetic markers.

Microarrays for genotyping human group a rotavirus by multiplex capture and type-specific primer extension.

Human group A rotavirus (HRV) is the major cause of severe gastroenteritis in infants worldwide. HRV shares the feature of a high degree of genetic diversity with many other RNA viruses, and therefore, genotyping of this organism is more complicated than genotyping of more stable DNA viruses. We describe a novel microarray-based method that allows high-throughput genotyping of RNA viruses with a high degree of polymorphism by multiplex capture and type-specific extension on microarrays. Denatured reverse transcription (RT)-PCR products derived from two outer capsid genes of clinical isolates of HRV were hybridized to immobilized capture oligonucleotides representing the most commonly occurring P and G genotypes on a microarray. Specific primer extension of the type-specific capture oligonucleotides was applied to incorporate the fluorescent nucleotide analogue cyanine 5-labeled dUTP as a detectable label. Laser scanning and fluorescence detection of the microarrays was followed by visual or computer-assisted interpretation of the fluorescence patterns generated on the microarrays. Initially, the method detected HRV in all 40 samples and correctly determined both the G and the P genotypes of 35 of the 40 strains analyzed. After modification by inclusion of additional capture oligonucleotides specific for the initially unassigned genotypes, all genotypes could be correctly defined. The results of genotyping with the microarray fully agreed with the results obtained by nucleotide sequence analysis and sequence-specific multiplex RT-PCR. Owing to its robustness, simplicity, and general utility, the microarray-based method may gain wide applicability for the genotyping of microorganisms, including highly variable RNA and DNA viruses.