VSITA, an Improved Approach of Target Amplification in the Identification of Viral Pathogens

Objective Unbiased next generation sequencing（NGS） is susceptible to interference from host or environmental sequences. Consequently, background depletion and virome enrichment techniques are usually needed for clinical samples where viral load is much lower than background sequences. Methods A viral Sequence Independent Targeted Amplification（VSITA） approach using a set of non-ribosomal and virus-enriched octamers（V8） was developed and compared with traditionally used random hexamers（N6）. Forty-five archived clinical samples of different types were used in parallel to compare the V8 and N6 enrichment performance of viral sequences and removal performance of ribosomal sequences in the step of reverse transcription followed by quantitative PCR（qP CR）. Ten sera samples from patients with fever of unknown origin and 10 feces samples from patients with diarrhea of unknown origin were used in comparison of V8 and N6 enrichment performance following NGS analysis. Results A minimum 30 hexamers matching to viral reference sequences（sense and antisense） were selected from a dataset of random 4,096（4~6） hexamers（N6）. Two random nucleotides were added to the 5＇ end of the selected hexamers, and 480（30 × 4~2） octamers（V8） were obtained. In general, VSITA approach showed higher enrichment of virus-targeted c DNA and enhanced ability to remove unwanted ribosomal sequences in the majorities of 45 predefined clinical samples. Moreover, VSITA combined with NGS enabled to detect not only more viruses but also achieve more viral reads hit and higher viral genome coverage in 20 clinical samples with diarrhea or fever of unknown origin. Conclusion The VSITA approach designed in this study is demonstrated to possess higher sensitivity and broader genome coverage than traditionally used random hexamers in the NGS-based identification of viral pathogens directly from clinical samples.

Co-infection of Chlamydia psittaci and Tropheryma whipplei: A case report

BACKGROUND The co-infection of Chlamydia psittaci(C.psittaci)and Tropheryma whipplei(T.whipplei)is unusual,and the detection of pathogenic microorganisms is particularly important for patients with severe diseases or poor experience in treatment.Early identification of pathogens can significantly improve the prognosis of the patients.Targeted next-generation sequencing(tNGS)is currently widely used in clinical practice for various infectious diseases,including respiratory infections,to achieve early,accurate,and rapid microbial diagnosis.CASE SUMMARY We report a case of a 40-year-old female patient with a history of contact with parrots who was diagnosed with C.psittaci and T.whipplei infection through bronchial lavage fluid targeted next generation sequencing.After moxifloxacin treatment,the patient's symptoms improved significantly,and the imaging changes were obviously resolved.CONCLUSION Coinfection with C.psittaci and T.whipplei is not common.In this case,timely and accurate identification of both pathogens was achieved using tNGS.Moreover,the efficacy of monotherapy with moxifloxacin was confirmed.

The clinical and genetic characteristics in children with mitochondrial disease in China

Mitochondrial disease was a clinically and genetically heterogeneous group of diseases, thus the diagnosis was very difficult to clinicians. Our objective was to analyze clinical and genetic characteristics of children with mitochondrial disease in China. We tested 141 candidate patients who have been suspected of mitochondrial disorders by using targeted next-generation sequencing(NGS), and summarized the clinical and genetic data of gene confirmed cases from Neurology Department, Beijing Children's Hospital, Capital Medical University from October 2012 to January 2015. In our study, 40 cases of gene confirmed mitochondrial disease including eight kinds of mitochondrial disease, among which Leigh syndrome was identified to be the most common type, followed by mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes(MELAS). The age-of-onset varies among mitochondrial disease, but early onset was common. All of 40 cases were gene confirmed, among which 25 cases(62.5%)with mitochondrial DNA(mtDNA) mutation, and 15 cases(37.5%) with nuclear DNA(nDNA) mutation. M.3243A>G(n=7)accounts for a large proportion of mtDNA mutation. The nDNA mutations include SURF1(n=7),PDHA1(n=2),and NDUFV1,NDUFAF6, SUCLA2, SUCLG1, RRM2 B, and C12orf65, respectively.