Pyrosequencing of a short hypervariable 16S rDNA fragment for the identification of nontuberculous mycobacteria--a comparison with conventional 16S rDNA sequencing and phenotyping

Direct identification of mycobacteria from liquid media using a triplex real-time PCR coupled with pyrosequencing method

Culture in enriched broth, as well as on a solid medium, is recommended for primary isolation of mycobacteria. With the introduction of liquid mycobacterial culture methods, a substantial workload regarding the identification of culture-recovered mycobacterial species, particularly Mycobacterium tuberculosis complex (MTC), has been imposed on our laboratory. We thus developed a triplex, real-time PCR coupled with pyrosequencing assay that can directly identify mycobacterial species from liquid media, which can reduce the workload. In this assay, real-time PCR simultaneously detects MTC and Mycobacterium xenopi, and amplifies the region of 16S rRNA gene containing hypervariable region A for pyrosequencing analysis; subsequent, pyrosequencing identifies many other nontuberculous mycobacteria. The assay was evaluated using 333 DNA samples directly prepared from liquid media, including 24 reference strains and 309 clinical isolates. Three hundred and twenty-eight (98.5%) of the 333 samples were correctly identified. The remaining five were determined as indeterminate. In conclusion, this coupled assay would be an alternative method for rapid identification of mycobacteria directly from liquid media in a clinical laboratory with a high workload in regions where tuberculosis is endemic.

Rapid identification of strains belonging to the Mycobacterium abscessus group through erm(41) gene pyrosequencing

Mycobacterium abscessus and Mycobacterium massiliense lung infections have different clarithromycin susceptibilities, making proper identification important; however, standard multi-gene sequencing in clinical laboratories is laborious and time consuming. We developed a pyrosequencing-based method for rapid identification of strains belonging to the M. abscessus group by targeting erm(41). We examined 55 isolates from new pulmonary M. abscessus infections and identified 28 M. abscessus, 25 M. massiliense, and 2 Mycobacterium bolletii isolates. Multi-gene sequencing of 16S rRNA, hsp65, rpoB, and the 16S-23S ITS region was concordant with the results of erm(41) pyrosequencing; thus, the M. abscessus group can be identified by single-nucleotide polymorphisms in erm(41). The method also enables rapid identification of polymorphic, inducible clarithromycin-resistant sequevars (T28 or C28). Pyrosequencing of erm(41) is a rapid, reliable, high-throughput alternative method for identifying and characterizing M. abscessus species. Further testing of a diverse collection of isolates is necessary to demonstrate the discriminatory power of erm(41) sequencing to differentiating species with this highly divergent group.

Laboratory diagnosis of tuberculosis in resource-poor countries: challenges and opportunities

With an estimated 9.4 million new cases globally, tuberculosis (TB) continues to be a major public health concern. Eighty percent of all cases worldwide occur in 22 high-burden, mainly resource-poor settings. This devastating impact of tuberculosis on vulnerable populations is also driven by its deadly synergy with HIV. Therefore, building capacity and enhancing universal access to rapid and accurate laboratory diagnostics are necessary to control TB and HIV-TB coinfections in resource-limited countries. The present review describes several new and established methods as well as the issues and challenges associated with implementing quality tuberculosis laboratory services in such countries. Recently, the WHO has endorsed some of these novel methods, and they have been made available at discounted prices for procurement by the public health sector of high-burden countries. In addition, international and national laboratory partners and donors are currently evaluating other new diagnostics that will allow further and more rapid testing in point-of-care settings. While some techniques are simple, others have complex requirements, and therefore, it is important to carefully determine how to link these new tests and incorporate them within a country's national diagnostic algorithm. Finally, the successful implementation of these methods is dependent on key partnerships in the international laboratory community and ensuring that adequate quality assurance programs are inherent in each country's laboratory network.

Pyrosequencing identification of Mycobacterium tuberculosis W-Beijing

Background

The worldwide expanding Mycobacterium tuberculosis W-Beijing family is associated with treatment failure and relapse. Its identification currently relies on spoligotyping and conventional sequencing. We developed pyrosequencing as an alternative method for its identification.

Findings

Pyrosequencing found a G/A substitution in the Rv0927c-pstS3 intergenic spacer and a RD105 deletion, identifying 8/104 M. tuberculosis isolates as W-Beijing isolates. In addition, pyrosequencing found a previously unreported TGC deletion in the Rv0927c gene of W-Beijing isolates. Total concordance was found between the pyrosequencing data and conventional sequencing, as well as reference molecular identification. Multispacer Sequence Typing assigned the W-Beijing isolates to the Asian lineage and the 96 non-W-Beijing isolates to the Euro-American lineage (P < 10^-5). The W-Beijing isolates were all susceptible to streptomycin, rifampin, isoniazid, ethambutol, and pyrazinamide; no resistance-associated mutations were detected in these eight W-Beijing isolates. There were no statistically significant differences in the antibiotic susceptibility of W-Beijing and non-W-Beijing isolates (p = 0.2, X² test). Pyrosequencing correctly identified M. tuberculosis organisms in 26/26 sputum specimens exhibiting acid-fast bacilli. Pyrosequencing results were obtained within four hours, incurring an estimated cost of 1.86 €/test.

Conclusion

Pyrosequencing of the Rv0927c gene and adjacent intergenic spacer is an efficient, low-cost technique for the rapid identification of W-Beijing isolates.

Evaluation of the bacterial diversity in the feces of cattle using 16S rDNA bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP)

BACKGROUND

The microbiota of an animal's intestinal tract plays important roles in the animal's overall health, productivity and well-being. There is still a scarcity of information on the microbial diversity in the gut of livestock species such as cattle. The primary reason for this lack of data relates to the expense of methods needed to generate such data. Here we have utilized a bacterial tag-encoded FLX 16s rDNA amplicon pyrosequencing (bTEFAP) approach that is able to perform diversity analyses of gastrointestinal populations. bTEFAP is relatively inexpensive in terms of both time and labor due to the implementation of a novel tag priming method and an efficient bioinformatics pipeline. We have evaluated the microbiome from the feces of 20 commercial, lactating dairy cows.

RESULTS

Ubiquitous bacteria detected from the cattle feces included Clostridium, Bacteroides, Porpyhyromonas, Ruminococcus, Alistipes, Lachnospiraceae, Prevotella, Lachnospira, Enterococcus, Oscillospira, Cytophage, Anaerotruncus, and Acidaminococcus spp. Foodborne pathogenic bacteria were detected in several of the cattle, a total of 4 cows were found to be positive for Salmonella spp (tentative enterica) and 6 cows were positive for Campylobacter spp. (tentative lanienae).

CONCLUSION

Using bTEFAP we have examined the microbiota in the feces of cattle. As these methods continue to mature we will better understand the ecology of the major populations of bacteria the lower intestinal tract. This in turn will allow for a better understanding of ways in which the intestinal microbiome contributes to animal health, productivity and wellbeing.