Ion Torrent PGMTM Platform Research Articles

Determinants of resistance in Bacteroides fragilis strain BFR_KZ01 isolated from a patient with peritonitis in Kazakhstan

ObjectivesBacteroides fragilis is one of the most important human anaerobic pathogens often found in various clinical infections. The purpose of this study was to determine the susceptibility of a B. fragilis clinical strain (BFR_KZ01) from Kazakhstan to the most commonly used anti-anaerobic drugs at the local level and to detect genes associated with resistance to these antibiotics. MethodsSpecies identification of the bacterial isolate was performed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS) and 16S rRNA gene sequencing. Susceptibility to broad-spectrum antibiotics (metronidazole, meropenem, ciprofloxacin, clindamycin and tetracycline) most commonly used for the treatment of intra-abdominal infections (IAIs) was determined. Mass spectra groups essential for identifying cfiA-positive strains among clinical isolates were studied using ClinProTools 3.0.22 software. An Ion Torrent PGM™ platform was used for whole-genome sequencing (WGS) of the studied isolate. ResultsThe resulting WGS data of strain BFR_KZ01 was submitted to GenBank. In total, 5300 coding sequences (CDSs) and 69 RNA genes were determined. Analysis of the whole-genome data revealed that the studied strain harbours cfiA, nimB, tetQ and gyrA genes conferring resistance to key drugs used in treatment of the IAIs. MALDI-TOF/MS analysis assigned strain BFR_KZ01 to Group II (cfiA-positive); however, BFR_KZ01 was phenotypically sensitive to meropenem (mean MIC, 1.3 mg/L). ConclusionDeterminants of drug resistance in strain BFR_KZ01 were identified. It was revealed that B. fragilis strain BFR_KZ01 from Kazakhstan is multidrug-resistant since it carries nimB, tetQ and gyrA genes conferring resistance to metronidazole, tetracycline and ciprofloxacin.

Phenylketonuria Diagnosis by Massive Parallel Sequencing and Genotype-Phenotype Association in Brazilian Patients.

Phenylketonuria (PKU) is a common inborn error of amino acid metabolism in which the enzyme phenylalanine hydroxylase, which converts phenylalanine to tyrosine, is functionally impaired due to pathogenic variants in the PAH gene. Thirty-four Brazilian patients with a biochemical diagnosis of PKU, from 33 unrelated families, were analyzed through next-generation sequencing in the Ion Torrent PGM™ platform. Phenotype–genotype correlations were made based on the BioPKU database. Three patients required additional Sanger sequencing analyses. Twenty-six different pathogenic variants were identified. The most frequent variants were c.1315+1G>A (n = 8/66), c.473G>A (n = 6/66), and c.1162G>A (n = 6/66). One novel variant, c.524C>G (p.Pro175Arg), was found in one allele and was predicted as likely pathogenic by the American College of Medical Genetics and Genomics (ACMG) criteria. The molecular modeling of p.Pro175Arg indicated that this substitution can affect monomers binding in the PAH tetramer, which could lead to a change in the stability and activity of this enzyme. Next-generation sequencing was a fast and effective method for diagnosing PKU and is useful for patient phenotype prediction and genetic counseling.

Identification and characterization of SNPs in released, landrace and wild accessions of mungbean (Vigna radiata (L.) Wilczek) using whole genome re-sequencing

Mungbean [Vigna radiata (L.) R. Wilczek var. radiata] is vital grain legume having nutritional and socio-economic importance, especially in the developing countries. We performed whole-genome re-sequencing of three accessions representing the wild progenitor species, released and landrace of mungbean to identify SNPs with relevance to genetic relationships analysis. Approximately 9.3 million raw reads were obtained using Ion Torrent PGM™ platform and more than 92% of the reads were mapped to the reference mungbean genome. We identified a total of 233,799 single-nucleotide polymorphisms in relation to the reference genome (SNPs: 103,341 in wild, 93,078 in released and 37,380 in landrace accessions) and 9544 insertions and deletions (InDels: 4742 in wild, 3608 in released and 1194 in landrace accessions) in the coding and non-coding regions. In all accessions, genomic variants were unevenly distributed within and across the mungbean chromosomes. Among these 5339, 4739 and 1795 SNPs were non-synonymous in 815, 790 and 317 genes of wild, released and landrace accessions, respectively. These polymorphisms might contribute to the variation in important pathways of genes for abiotic and biotic stress tolerance and important agronomic traits, such as seed dormancy, flowering time and seed size in mungbean. Among the randomly selected SNPs, a selected subset was validated using Sanger sequencing technique. The genomic variations among mungbean wild, released and landrace accessions constitute a powerful tool to support genetic research and molecular breeding of mungbean.

A case study of salivary microbiome in smokers and non-smokers in Hungary: analysis by shotgun metagenome sequencing

ABSTRACT Objective To investigate the role of cigarette smoking in disease-development through altering the composition of the oral microbial community. Periodontitis and oral cancer are highly prevalent in Hungary; therefore, the salivary microbiome of smoker and non-smoker Hungarian adults was characterized. Methods Shotgun metagenome sequencing of salivary DNA samples from 22 individuals (11 non-smokers and 11 current smokers) was performed using the Ion Torrent PGMTM platform. Quality-filtered reads were analysed by both alignment-based sequence similarity searches and genome-centric binning. Results Prevotella, Veillonella and Streptococcus were the predominant genera in the saliva of both groups. Although the overall composition and diversity of the microbiota were similar, Prevotella was significantly more abundant in salivary samples of current smokers compared to non-smokers. Members of the genus Prevotella were implicated in the development of inflammatory diseases and oral cancer. The abundance of the genus Megasphaera also increased in current smokers, whereas the genera Neisseria, Oribacterium, Capnocytophaga and Porphyromonas were significantly reduced. The data generated by read-based taxonomic classification and genome-centric binning mutually validated the two distinct metagenomic approaches. Conclusion Smoking-associated dysbiosis of the salivary microbiome in current cigarette smokers, especially increased abundance of Prevotella and Megasphaera genera, may facilitate disease development.

Analysis of CSF1PO and D18S51 Loci Based on Ion Torrent PGM™ Platform.

To analyse and detect CSF1PO and D18S51 loci by next generation sequencing （NGS） technology for the study on their sequence polymorphism. The peripheral blood samples were collected from 165 unrelated individuals of Chinese Han population. DNA samples were obtained by QIAamp DNA Mini kit. The library was constructed by Ion Plus Fragment Library. DNA sequencing analysis was performed on Ion Torrent PGM™ Platform. The newfound alleles were verified by Sanger sequencing. Data were analysed by Torrent Suite™ v5.0.2 and Integrative Genomics Viewer for the genotype identification and frequency count. The data were analysed statistically by PowerState v12. The length and sequence polymorphisms of CSF1PO and D18S51 loci were simultaneously obtained by NGS technology. A new genotype was found on CSF1PO locus, and two new genotypes on D18S51 locus. Sanger sequencing was used to verify the newfound alleles found by NGS technology, and the results of verification showed consistency. The structure of core repeats on CSF1PO and D18S51 loci was detected by NGS in this study for the improvement of the identifying performance of locus.

Frequencies of the precision ID ancestry panel markers in Basques using the Ion Torrent PGMTM platform

The Precision ID Ancestry Panel for the Ion Torrent PGM™ platform is able to genotype 165 autosomal SNPs by massively parallel sequencing (MPS). In the present study, we evaluated the depth of coverage, the locus strand balance and the heterozygote balance of the above panel. The SNPs rs1569175, rs2306040, rs9845457, rs1407434, and rs10007810 showed a low performance, due either to a low coverage, locus strand imbalance or heterozygote imbalance. To further to assess this panel, we analyzed 108 Basques. All loci proved to be in Hardy-Weinberg equilibrium and we did not detect any association between them with the exception of the pair rs3916235-rs4891825 in chromosome 18. The forensic parameters combined match probability and combined power of exclusion were estimated to be 3.13×10−35 and 99.9972%, respectively. In conclusion, the Precision ID Ancestry panel along with this new MPS technology constitute a very promising tool for human identification and biogeographical ancestry inference in routine casework in the forensic field.

Whole Genome Sequencing of Human mtDNA Based on Ion Torrent PGM™ Platform

To analyze and detect the whole genome sequence of human mitochondrial DNA （mtDNA） by Ion Torrent PGM™ platform and to study the differences of mtDNA sequence in different tissues. Samples were collected from 6 unrelated individuals by forensic postmortem examination, including chest blood, hair, costicartilage, nail, skeletal muscle and oral epithelium. Amplification of whole genome sequence of mtDNA was performed by 4 pairs of primer. Libraries were constructed with Ion Shear™ Plus Reagents kit and Ion Plus Fragment Library kit. Whole genome sequencing of mtDNA was performed using Ion Torrent PGM™ platform. Sanger sequencing was used to determine the heteroplasmy positions and the mutation positions on HVⅠ region. The whole genome sequence of mtDNA from all samples were amplified successfully. Six unrelated individuals belonged to 6 different haplotypes. Different tissues in one individual had heteroplasmy difference. The heteroplasmy positions and the mutation positions on HVⅠ region were verified by Sanger sequencing. After a consistency check by the Kappa method, it was found that the results of mtDNA sequence had a high consistency in different tissues. The testing method used in present study for sequencing the whole genome sequence of human mtDNA can detect the heteroplasmy difference in different tissues, which have good consistency. The results provide guidance for the further applications of mtDNA in forensic science.

Allele frequencies and other forensic parameters of the HID-Ion AmpliSeq™ Identity Panel markers in Basques using the Ion Torrent PGM™ platform

The HID-Ion AmpliSeq™ Identity Panel amplifies 90 autosomal SNPs and 34 Y- SNPs with massively parallel sequencing (MPS) using the Ion Torrent PGM™ platform. In the present study, 105 Basques were analyzed to assess this panel. All loci were in Hardy-Weinberg equilibrium and no association between them was detected. Forensic parameters were calculated as 5.74×10−36 for combined match probability and 99.99998% for combined power of exclusion. In conclusion, the HID Identity panel and the use of this new MPS technology are very promising tools for paternity testing and human identification in routine casework in the forensic field.

Transcriptome sequencing and development of novel genic SSR markers for Dendrobium officinale

Dendrobium officinale is a critically endangered and valuable medicinal herb. In this study, two transcriptome libraries were constructed from 2-year-old stems of two cultivated varieties and sequenced with the Ion Torrent PGM™ platform. A total of 51,683 all-transcripts with average length of 505 bp, and 40,405 all-unigenes with N50 of 644 bp were achieved. Totally, 8527 potential genic simple sequence repeats (SSRs) were identified from 7332 (18.15%) unigene sequences, of which 1023 (2.53%) unigenes contained more than one SSR. Finally, 68 locus-specific primer pairs were designed, and 17 of them produced polymorphic products in D. officinale individuals. The number of alleles per locus ranged from 2 to 15, the observed and expected heterozygosity estimates ranged from 0.194 to 0.903 and from 0.360 to 0.893, respectively. These loci were further tested for cross-species transferability to D. huoshanense. All the 17 primer pairs were successfully amplified to yield locus-specific PCR products in D. huoshanense. Due to their high level of polymorphism and transferability, these genic SSR markers are valuable tools not only for germplasm conservation of this species but also for phylogenetic studies of Dendrobium.

Mutation spectrum of NF1 gene in Italian patients with neurofibromatosis type 1 using Ion Torrent PGM™ platform

Neurofibromatosis type 1 (NF1) is caused by mutations of the NF1 gene and is one of the most common human autosomal dominant disorders. The patient shows different signs on the skin and other organs from early childhood. The best known are six or more café au lait spots, axillary or inguinal freckling, increased risk of developing benign nerve sheath tumours and plexiform neurofibromas. Mutation detection is complex, due to the large gene size, the large variety of mutations and the presence of pseudogenes. Using Ion Torrent PGM™ Platform, 73 mutations were identified in 79 NF1 Italian patients, 51% of which turned out to be novel mutations. Pathogenic status of each variant was classified using “American College of Medical Genetics and Genomics” guidelines criteria, thus enabling the classification of 96% of the variants identified as being pathogenic. The use of Next Generation Sequencing has proven to be effective as for costs, and time for analysis, and it allowed us to identify a patient with NF1 mosaicism. Furthermore, we designed a new approach aimed to quantify the mosaicism percentage using electropherogram of capillary electrophoresis performed on Sanger method.

Next generation sequencing of SNPs using the HID-Ion AmpliSeq™ Identity Panel on the Ion Torrent PGM™ platform

The HID-Ion AmpliSeq™ Identity Panel (the HID Identity Panel) is designed to detect 124-plex single nucleotide polymorphisms (SNPs) with next generation sequencing (NGS) technology on the Ion Torrent PGM™ platform, including 90 individual identification SNPs (IISNPs) on autosomal chromosomes and 34 lineage informative SNPs (LISNPs) on Y chromosome. In this study, we evaluated performance for the HID Identity Panel to provide a reference for NGS-SNP application, focusing on locus strand balance, locus coverage balance, heterozygote balance, and background signals. Besides, several experiments were carried out to find out improvements and limitations of this panel, including studies of species specificity, repeatability and concordance, sensitivity, mixtures, case-type samples and degraded samples, population genetics and pedigrees following the Scientific Working Group on DNA Analysis Methods (SWGDAM) guidelines. In addition, Southern and Northern Chinese Han were investigated to assess applicability of this panel. Results showed this panel led to cross-reactivity with primates to some extent but rarely with non-primate animals. Repeatable and concordant genotypes could be obtained in triplicate with one exception at rs7520386. Full profiles could be obtained from 100pg input DNA, but the optimal input DNA would be 1ng–200pg with 21 initial PCR cycles. A sample with ≥20% minor contributor could be considered as a mixture by the number of homozygotes, and full profiles belonging to minor contributors could be detected between 9:1 and 1:9 mixtures with known reference profiles. Also, this assay could be used for case-type samples and degraded samples. For autosomal SNPs (A-SNPs), FST across all 90loci was not significantly different between Southern and Northern Chinese Han or between male and female samples. All A-SNP loci were independent in Chinese Han population. Except for 18loci with He <0.4, most of the A-SNPs in the HID Identity Panel presented high polymorphisms. Forensic parameters were calculated as >99.999% for combined discrimination power (CDP), 0.999999724 for combined power of exclusion (CPE), 1.390×1011 for combined likelihood ratio (CLR) of trios, and 2.361×106 for CLR of motherless duos. For Y-SNPs, a total of 8 haplotypes were observed with the value of 0.684 for haplotype diversity. As a whole, the HID Identity Panel is a well-performed, robust, reliable and high informative NGS-SNP assay and it can fully meet requirements for individual identification and paternity testing in forensic science.

Evaluation of the Early Access STR Kit v1 on the Ion Torrent PGM™ platform

The Early Access STR Kit v1 is designed to detect 25-plex loci with next generation sequencing (NGS) technology on the Ion Torrent PGM™ platform, including 16 of 20 expanded Combined DNA Index System (CODIS) core loci (CSF1PO, D1S1656, D2S1338, D2S441, D3S1358, D5S818, D7S820, D8S1179, D10S1248, D13S317, D16S539, D19S433, D21S11, TH01, TPOX and vWA), 8 non-CODIS core loci (D1S1677, D2S1776, D4S2408, D5S2500.AC008791, D6S1043, D6S474, D9S2157 and D14S1434) and Amelogenin. In this study, we compared the Early Access STR Kit v1 with the Ion Torrent™ HID STR 10-plex to find out its improvements and explored an appropriate analytical threshold to enhance the performance. In addition, seven experiments were conducted to evaluate the Early Access STR Kit v1 such as studies of repeatability, concordance, sensitivity, mixtures, degraded samples, case-type samples and pedigrees. Other than a little discordance (0.95%) with CE-STR results observed at D21S11, NGS-STR results correctly reflected the sample being tested. Repeatable results were obtained from both initial PCRs and emPCRs aside from a few variations of allele coverage. Full profiles could be obtained from 100pg input DNA and >48.84% profiles from 10pg input DNA. Mixtures were easily detected at 9:1 and 1:9 ratios. This system could be adapted to case-type samples and degraded samples. As a whole, the Early Access STR Kit v1 is a robust, reliable and reproducible assay for NGS-STR typing and a potential tool for human identification.

Strategies for complete mitochondrial genome sequencing on Ion Torrent PGM™ platform in forensic sciences

Next generation sequencing (NGS) is a time saving and cost-efficient method to detect the complete mitochondrial genome (mtGenome) compared to Sanger sequencing. In this study we focused on developing strategies for mtGenome sequencing on the Ion Torrent PGM™ platform and NGS data analysis. With our experience, 4, 15 and 30 samples could be loaded onto Ion 314™, Ion 316™ and Ion 318™ chips respectively at a pooling concentration of 26pM, achieving to sufficient average coverage of ≥1500×and well strand balance of 1.05. Data processing software is essential to NGS mega data analysis. The in-house Perl scripts were developed for primary data analysis to screen out uncertain positions and samples from variant call format (VCF) reports and for pedigree study to perform pairwise comparisons. The Integrative Genomic Viewer (IGV) and the NextGENe software were introduced to secondary data analysis. The mthap and EMMA were employed for haplogroup assignment. The dataset was reviewed and approved by the EMPOP as the final version, which showed 2.66% error rate generated from the Torrent Variant Caller (TVC). Across the mtGenome, 4022 variants were found at 725 nucleotide positions, where ratio of transitions to transversions was estimated at 20.89:1 and 22.18% of variants was concentrated at hypervariable segments I and II (HVS-I and HVS-II). Totally, 107 complete mtGenome haplotypes were observed from 107 Northern Chinese Han and assigned to 88 haplogroups. The random match probability (RMP) of complete mtGenome was calculated as 0.009345794, decreasing 26.19% by comparison to that of HVS-I only, and the haplotype diversity (HD) was evaluated as 1, increasing 0.33% by comparison to that of HVS-I only. Principal component analysis (PCA) showed that our population was clustered to East and Southeast Asians. The strategies in this study are suitable for complete mtGenome sequencing on Ion Torrent PGM™ platform and Northern Chinese Han (EMP00670) is the first complete mtGenome dataset contributed to the EMPOP from East Asian.

Next-Generation Sequencing Workflow for NSCLC Critical Samples Using a Targeted Sequencing Approach by Ion Torrent PGM™ Platform.

Next-generation sequencing (NGS) is a cost-effective technology capable of screening several genes simultaneously; however, its application in a clinical context requires an established workflow to acquire reliable sequencing results. Here, we report an optimized NGS workflow analyzing 22 lung cancer-related genes to sequence critical samples such as DNA from formalin-fixed paraffin-embedded (FFPE) blocks and circulating free DNA (cfDNA). Snap frozen and matched FFPE gDNA from 12 non-small cell lung cancer (NSCLC) patients, whose gDNA fragmentation status was previously evaluated using a multiplex PCR-based quality control, were successfully sequenced with Ion Torrent PGM™. The robust bioinformatic pipeline allowed us to correctly call both Single Nucleotide Variants (SNVs) and indels with a detection limit of 5%, achieving 100% specificity and 96% sensitivity. This workflow was also validated in 13 FFPE NSCLC biopsies. Furthermore, a specific protocol for low input gDNA capable of producing good sequencing data with high coverage, high uniformity, and a low error rate was also optimized. In conclusion, we demonstrate the feasibility of obtaining gDNA from FFPE samples suitable for NGS by performing appropriate quality controls. The optimized workflow, capable of screening low input gDNA, highlights NGS as a potential tool in the detection, disease monitoring, and treatment of NSCLC.

Differences in the faecal microbiome of non-diarrhoeic clinically healthy dogs and cats associated with Giardia duodenalis infection: impact of hookworms and coccidia

The protozoan parasite Giardia duodenalis causes a waterborne diarrhoeal disease in animals and humans, yet many Giardia-infected hosts remain asymptomatic. Mixed parasite infections are common in both animals and humans with unknown consequences for Giardia or other parasites. We compared the composition and diversity of bacterial communities from 40 dogs, including free-roaming dogs, and 21 surrendered cats from Australia. The dog cohort included 17 (42.5%) dogs positive for Giardia and 13 (32.5%) dogs positive for dog hookworm (Ancylostoma caninum). The cat samples included eight positive for Giardia and eight positive for Cystoisospora. The V4 region of 16S rRNA was sequenced at an average of 36,383 high quality sequences (>200bp) per sample using the Ion Torrent PGM™ platform. In dogs we found significant (P<0.05, AnoSim) difference between the Giardia-positive and -negative groups when evaluating bacterial genera. No such difference was demonstrated between Ancylostoma-positive and -negative dogs. However, there was a modest but not significant separation of the Giardia-negative and -positive dogs (P=0.09, UniFrac) using principal coordinate analysis. Removal of dogs with hookworms further separated Giardia-positive and -negative groupings (P=0.06, UniFrac). In cats, the presence of Giardia was not associated with a significant difference based on bacterial genera (P>0.05, AnoSim). Cystoisospora-positive cats, however, exhibited significantly different profiles from Cystoisospora-negative cats (P=0.02, AnoSim) and UniFrac showed significant separation of Cystoisospora-positive and -negative samples (P<0.01). The results suggest that in clinically heathy dogs and cats, helminths and protozoa are associated with different microbiomes and possibly variable gut microbiota functions. Understanding the association of parasites and microbiomes has important consequences for the administration of antiparasitic drugs in animals and humans.

Abstract 3580: Hotspot mutation and fusion transcript detection from the same non-small lung adenocarcinoma sample

Abstract The presence of certain chromosomal rearrangements and the subsequent fusion gene derived from translocations has been implicated in a number of cancers. Hundreds of translocations have been described in the literature recently but the need to efficiently detect and further characterize these chromosomal translocations is growing exponentially. The two main methods to identify and monitor translocations, fluorescent in situ hybridization (FISH) and comparative genomic hybridization (CGH) are challenging, labor intensive, the information obtained is limited, and sensitivity is rather low. Common sample types for these analyses are biopsies or small tumors, which are very limited in material making the downstream measurement of more than one analyte rather difficult; obtaining another biopsy, using a different section or splitting the sample can raise issues of tumor heterogeneity. The ability to study mutation status as well as measuring fusion transcript expression from the same sample is powerful because you're maximizing the information obtained from a single precious sample and eliminating any sample to sample variation. Here we describe the efficient isolation of two valuable analytes, RNA and DNA, from the same starting sample without splitting, followed by versatile and informative downstream analysis. This methodology was applied to FFPE and degraded samples as well as fresh tissues and cells. DNA and RNA were recovered from the same non-small lung adenocarcinoma sample and both mutation analysis, as well as fusion transcript detection was performed using the Ion Torrent PGM™ platform on the same Ion 318™ chip. Using 10ng of DNA and 10ng of RNA input, we applied the Ion AmpliSeq™ Colon and Lung Cancer panel to analyze over 500 COSMIC mutations in 22 genes and the Ion AmpliSeq™ RNA Lung Fusion panel to detect 40 different fusion transcripts. Citation Format: Angie Cheng, Varun Bagai, Joey Cienfuegos, Natalie Hernandez, Mu Li, Jeff Schageman, Richard Fekete, Rosella Petraroli, Alexander Vlassov, Susan Magdaleno. Hotspot mutation and fusion transcript detection from the same non-small lung adenocarcinoma sample. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3580. doi:10.1158/1538-7445.AM2014-3580