Round Of Polymerase Chain Reaction Research Articles

Single-round QuikChange PCR for engineering multiple site-directed mutations in plasmid DNA

Mutational study is a cornerstone methodology in biochemistry and genetics, and many mutagenesis strategies have been invented to promote the efficiency of gene engineering. In this study, we developed a simple and timesaving approach to integrate simultaneous mutagenesis at discrete sites. By using plasmid as a template and compatible oligonucleotide primers per the QuikChange strategy, our method was able to introduce multiple nucleotide insertions, deletions and replacements in one round of polymerase chain reaction. The longest insertion and deletion were achieved with 28 bp and 16 bp mismatch respectively. For minor nucleotide replacements (mismatch no more than 4 bp), mutations were achieved at up to 4 discrete locations. Usually, a successful clone with all desired mutations was found by screening 5 colonies. Clones with a subset of mutations may be stocked into the library of mutants or used as templates in the next rounds of mutagenic PCR to accomplish the entire construction project. This method can be applied to build up a combinatory library of mutants through saturation mutagenesis at multiple sites. It is promising to facilitate the research of protein biochemistry, forward genetics and synthetic biology.

Boron nitride nanoplate-based improvement of the specificity and sensitivity in loop-mediated isothermal amplification for Vibrio parahaemolyticus detection

BackgroundNucleic acid testing based on DNA amplification is gradually entering people's modern life for clinical diagnosis, food safety monitoring and infectious disease prevention. Polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP) are the most powerful techniques that have been the gold standard for quantitative nucleic acid analysis. However, the high nonspecific amplification rate caused by the formation of primer dimers, hairpin structures and mismatched hybridization severely restricts their real-world applications. It is highly desirable to explore a way for improving the specificity and sensitivity of PCR and LAMP assays. ResultsIn this work, we demonstrated that a nanomaterial boron nitride nanoplate (BNNP), due to its unique surface properties, can interact with the main components of the amplification reaction, such as single stranded primers and Bst DNA polymerase, and increase the thermal conductivity of the solution. As a result, the presence of BNNPs dramatically improved the specificity of PCR and LAMP. And BNNPs maintained the specificity even after five rounds of PCR. Moreover, the sensitivity of LAMP was also enhanced by BNNPs, and the detection limit of BNNP-based LAMP was two orders of magnitude lower than that of classical LAMP. Then the BNNP-based LAMP was applied to detect Vibrio parahaemolyticus in contaminated seafood samples with high specificity and a 10-fold increase in sensitivity. SignificanceThis is the first systematic demonstration of BNNPs as a promising additive to enhance the efficiency and fidelity of PCR and LAMP amplification reactions, thereby greatly expanding the application of nucleic acid detection in a wide range of laboratory and clinical settings.

Hepatitis C subtyping assay failure in UK patients born in sub-Saharan Africa: Implications for global treatment and elimination.

HCV serum derived from 146 individuals, whose likely source of infection was from sub-Saharan Africa (SSA) was investigated with a novel panel of single round polymerase chain reaction(PCR) assays targeting NS5B and NS5A genomic regions. Virus subtype assignments were determined by pairwise-distance analysis and compared to both diagnostic laboratory assignments and free-to-use online typing tools. Partial NS5A and NS5B sequences were respectively obtained from 131 to 135 HCV-positive patients born in 19 different countries from SSA but attending clinics in the UK. We determined that routine clinical diagnostic methods incorrectly subtyped 59.0% of samples, with a further 6.8% incorrectly genotyped. Of five commonly used online tools, Geno2Pheno performed most effectively in determining a subtype in agreement with pairwise distance analysis. This study provides a simple low-cost pathway to accurately subtype in SSA, guide regional therapeutic choice and assist global surveillance and elimination initiatives.

E6-E7 based nested multiplex PCR assay for genital HPV detection and simultaneous typing of 15 high and low-risk HPV types

PurposeDue to a wide range of Human Papillomavirus (HPV) types associated with genital cancers; HPV genotyping remains important for the introduction of an appropriate vaccine, disease diagnosis, follow-up and epidemiological surveys. Currently, available molecular genotyping assays are not only expensive but also requires dedicated and expensive equipment which is not feasible in the majority of low-and-middle-socioeconomic countries. The purpose of the study was to develop and evaluated a cost-effective nested-multiplex polymerase chain reaction (NM-PCR) assay for HPV genotyping. MethodsHPV-DNA containing plasmids and cervical scrapings from histologically confirmed cervical cancer cases were used to evaluate the NM-PCR. In the first round PCR, a set of consensus primers were used to amplify 38 mucosal HPV types. HPV Type-specific primers were used in the second-round polymerase chain reaction (PCR) to amplify 15 HPV types in three multiplex cocktails. The assay sensitivity was determined with the control panel containing one to 1010genome equivalents (GE). DNA sequencing was done to confirm the PCR results. ResultsThe assay was able to amplify all HPV types and detected as few as 50GE per reaction. A total of 23 endo-cervical samples obtained from healthy, HPV negative subjects and 52 histologically confirmed cervical scrapings were processed for HPV genotyping by NM-PCR. HPV DNA was detected in all histologically confirmed samples. DNA sequencing results showed complete concordance with PCR results. ConclusionsThe designed nested PCR based assay had good concordance with clinical histology and sequencing results and appears to be a promising tool for HPV genotyping especially in resource-constrained settings.

DNA diagnostics for reliable and universal identification of Helicobacter pylori.

Reliable diagnostics are a major challenge for the detection and treatment of Helicobacter pylori (H. pylori) infection. Currently at the forefront are non-invasive urea breath test (UBT) and stool antigen test (SAT). Polymerase chain reaction (PCR) is not endorsed due to nonspecific primers and the threat of false-positives. The specificity of DNA amplification can be achieved by nested PCR (NPCR), which involves two rounds of PCR. If the primers are properly designed for the variable regions of the 16S rRNA gene, it is not difficult to develop an NPCR assay for the unambiguous identification of H. pylori. Elaborate NPCR for a 454 bp amplicon was validated on 81 clinical biopsy, stool, and saliva samples, each from the same individuals, and compared with available H. pylori assays, namely histology, rapid urease test, SAT, and 13C-UBT. The assay was much more sensitive than simple PCR, and it was equally sensitive in biopsy samples as the 13C-UBT test, which is considered the gold standard. In addition, it is sufficiently specific because sequencing of the PCR products exclusively confirmed the presence of H. pylori-specific DNA. However, due to the threshold and lower abundance, the sensitivity was much lower in amplifications from stool or saliva. Reliable detection in saliva also complicates the ability of H. pylori to survive in the oral cavity aside from and independent of the stomach. The reason for the lower sensitivity in stool is DNA degradation; therefore, a new NPCR assay was developed to obtain a shorter 148 bp 16S rRNA amplicon. The assay was validated on stool samples from 208 gastroenterological patients and compared to SAT results. Surprisingly, this NPCR revealed the presence of H. pylori in twice the number of samples as SAT, indicating that many patients are misdiagnosed, not treated by antibiotics, and their problems are interpreted as chronic. Thus, it is unclear how to properly diagnose H. pylori in practice. In the first approach, SAT or UBT is sufficient. If samples are negative, the 148 bp amplicon NPCR assay should be performed. If problems persist, patients should not be considered negative, but due to threshold H. pylori abundance, they should be periodically tested. The advantage of NPCR over UBT is that it can be used universally, including questionable samples taken from patients with achlorhydria, receiving proton pump inhibitors, antibiotics, bismuth compound, intestinal metaplasia, or gastric ulcer bleeding.

Validation of Next Generation Sequencing-Based Clonality Assays for Diagnosis and Minimal Residual Disease Tracking in Lymphoid Malignancies

Introduction:B or T cell receptor (BCR/TCR) clonal rearrangements have served as important diagnostic markers and minimal residual disease (MRD) tracking markers to guide treatment decisions in lymphoid malignancies. Next generation sequencing (NGS)-based BCR/TCR clonality assessment allows easier sample preparation, higher sensitivity and simpler standardization than flow cytometry and polymerase chain reaction (PCR)-based assays. Here, we developed NGS-based BCR/TCR clonality assays to identify and track disease-associated clonotypes of IGH, IGK, IGL, TCRB and TCRG rearrangements and BCL1/2-IGH translocations in lymphoid malignant cells. Our studies validated the analytical performance of the assays using genomic DNA (gDNA) from cell lines and patient samples diagnosed with acute lymphoblastic leukemia (ALL), multiple myeloma (MM), chronic lymphocytic leukemia (CLL), lymphoma and lymphoid blast phase chronic myeloid leukemia (BP-CML), as well as peripheral blood gDNA and circulating tumor DNA (ctDNA) from lymphoma patients.Methods:Our BCR/TCR clonality assays were based on two rounds of multiplex PCR followed by NGS. In the first-round PCR, the sequences of complementary determining region 3 (CDR3) in rearranged immune receptor genes were amplified by multiplex primers, and sample-specific index and NGS adapters were then added in the second-round PCR. Sequencing was performed on NovaSeq 6000 System and processed with customized bioinformatics pipelines. BCR clonality assays could identify IGH (V H-D H-J H or D H-J H), IGK (V κ-J κ, V κ-Kde and intronRSS-Kde) and IGL (V λ-J λ) rearrangements, as well as BCL1-IGH and BCL2-IGH translocations. TCR clonality assays could detect TCRB (V β-D β-J β) and TCRG (V γ-J γ) rearrangements. To evaluate the performance of our assays, we detected BCR or TCR clonality in gDNA from 4 cell lines and 40 clinical samples with ALL, MM, CLL and lymphoma, as well as paired chronic- and blast-phase samples of CML. Limit-of-detection (LOD) was estimated by clinical samples and cell lines with a background of peripheral blood gDNA from healthy donors. Linearity of detection was established with gDNA of cell lines spiked into normal gDNA to generate across orders of magnitude of clonal frequencies. To ensure consistent performance of the assays, we tested separate reactions and a single mixed reaction for IGH VDJ, IGH DJ, IGK and IGL. In addition, peripheral blood gDNA matching aforementioned lymphoma cases and ctDNA samples were also tested by our assays.Results:Both BCR clonality of B-cell lymphoid malignancies (B-ALL, MM, CLL and lymphoma) and TCR clonality of T-cell lymphoid malignancies (T-ALL and lymphoma) showed above 90% positive detection rate and mostly positive in more than one receptor gene. Chronic and blast phase samples from the same CML patient showed an identical dominant clonotype. The assays had high sensitivity, with LoD defined between 1 to 2 malignant cells in both BCR and TCR clonality assessment. Linearity was observed with clonal frequencies from 1 to 10 -6, which indicated consistence between observed and expected frequencies. The sequencing results with a single adjusted mixed reaction for IGH VDJ, IGH DJ, IGK and IGL were comparable to that with separate reactions, suitable for both diagnosed samples and MRD samples, suggesting the robustness of the assays. Our testing results also showed that peripheral blood gDNA of lymphoma patients carried identical clonotypes found in malignant tissues and ctDNA.Conclusion:We characterized and validated the performance of our NGS -based BCR/TCR clonality assays. We also demonstrated its potential application as a highly sensitive tool for diagnosis and MRD tracking for lymphoid malignancies, including ALL, MM, CLL, lymphoma and even CML at risk of lymphoid blast transformation. DisclosuresNo relevant conflicts of interest to declare.

Development and evaluation of a ligation-free sequence-independent, single-primer amplification (LF-SISPA) assay for whole genome characterization of viruses

Molecular identification and characterization of novel or re-emerging infectious pathogens is critical for disease surveillance and outbreak investigations. Next generation sequencing (NGS) using Sequence-Independent, Single-Primer Amplification (SISPA) is being used extensively in sequencing of viral genomes but it requires an expensive library preparation step. We developed a simple, low-cost method that enriches nucleic acids followed by a ligation-free (LF) 2-step Polymerase Chain Reaction (PCR) procedure for library preparation. A pan-chimeric universal primer (JS15N14) containing 15 nucleotides with a random tetradecamer (14N) attached to the 3′-end was designed. The complimentary primer (JS15) was used for nucleic acid enrichment in a first round PCR. A second PCR was designed to create Illumina sequencer-compatible sequencing-ready libraries for NGS. The new LF-SISPA protocol was tested using six RNA and DNA viral genomes (10.8–229.4 kilobases, kb) from an ATCC virome nucleic acid mix (ATCC® MSA-1008™) followed by analysis using One Codex, an online identification tool. In addition, a human stool sample known to be positive for norovirus GII was sequenced, and de novo assembly was performed using the Genome Detective Virus Tool allowing for near complete genome identification in less than 24 h. The LF-SISPA method does not require prior knowledge of target sequences and does not require an expensive enzymatic library preparation kit, thereby providing a simple, fast, low-cost alternative for the identification of unknown viral pathogens.

SARS-CoV-2 Screening Test for Japanese Returnees From Wuhan, China, January 2020.

BackgroundSevere acute respiratory syndrome–related coronavirus 2 (SARS-CoV-2) was found to be the causative microorganism of coronavirus disease 2019 (COVID-19), which started to spread in Wuhan, China. This study was to evaluate the effectiveness of questionnaire, symptoms-based screening, and polymerase chain reaction (PCR) screening of returnees from COVID-19-endemic areas on a chartered flight, to examine the proportion of infected persons and the proportion of asymptomatic persons among infected persons who returned from Wuhan.MethodsA retrospective cohort study was done in 7 tertiary medical institutions in Japan. A total of 566 Japanese who returned from Wuhan participated in the study.ResultsOverall, 11 of the 566 passengers had a positive SARS-CoV-2 PCR result for pharyngeal swabs and 6 were asymptomatic. Only fever differed between SARS-CoV-2-positive and -negative individuals (P < .043). Six of the 11 PCR-positive individuals were asymptomatic; 4 remained positive on day 10, and 1 asymptomatic person tested positive up to day 27. Two of the 11 were negative on the first PCR test and positive on the second.ConclusionsOur results will be important insights on screening returnees from locked-down cities, as well as providing important data on the proportion of asymptomatic individuals infected with SARS-CoV-2. A 13-day observation period and a second round of PCR may be effective to screen patients, including asymptomatic infections.

Low Cassette Variability in Class 2 and Class 1 Integrons of Aeromonas spp. Isolated from Environmental Samples

Integrons are prokaryotic genetic elements known to carry and exchange antibiotic resistance gene cassettes through a site-specific recombinase called integrase. In this work, 107 Aeromonas isolates from environmental origin, including fish, water, and sediments, were investigated for the presence of integrons. Using specific primers for Class 1, 2 and 3 integrases, only Class 1 and Class 2 integrons were detected. Detection of Class 2 integrases and their associated variable regions required two rounds of polymerase chain reaction (PCR). Sequencing of the intI2 amplicons confirmed them as integrase-derived products. Class 1 integrons were detected in 26 out of 107 isolates. PCR amplification of the variable regions associated to these integrons revealed an outstanding homogeneity, 25 of them having variable regions with an identical dfrA12-orfF-aadA2 cassette array and one integron carrying only the dfrA16 cassette. To assess clone diversity, chromosomal DNA from isolates was subjected to enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR), which discarded clonality in all instances. Class 2 integrons were surprisingly more prevalent than Class1 integrons, being detected in 60 out of 107 isolates. Forty-six of them showed a unique ERIC profile, while the remaining 14 strains displayed profiles that could be grouped in five different patterns. Cassette arrangements of all Class 2 variable regions were those described as the most prevalent (dfrA1-sat2-aadA1). A rather startling result of this work is the sensitivity to trimethoprim, streptomycin, and streptothricin of most strains, despite the presence of the cognate resistance genes. To know the integron distribution in environmental Aeromonas species, a phylogenetic reconstruction was done using rpoD/gyrB or rpoD/gyrA gene sequences. Isolates bearing these elements corresponded to Aeromonas hydrophila, Aeromonas veronii, Aeromonas salmonicida, Aeromonas dhakensis, Aeromonas sanarellii, Aeromonas taiwanensis, Aeromonas media, Aeromonas caviae, Aeromonas jandaei, and Aeromonas sp. This work revealed an unusual high incidence of Class 2 integrons and a low variability of cassette arrangements in environmental Aeromonas species.

Multisite-Directed Mutagenesis.

This protocol, suitable for both general and close-proximity mutagenesis, includes a simple and rapid procedure that combines polymerase chain reaction (PCR), DpnI digestion, and overlap extension. The key point of this approach is the use of overlap extension to form a circular DNA plasmid with mutations without the need for phosphorylated primers or ligase reactions. Essentially, during the first round of PCR, the new DNA is synthesized with nicks between the 3' ends of the synthesized DNA and the 5' ends of the first pair of primers. During successive rounds of PCR, a new pair of mutagenic oligonucleotides leads to the synthesis of two DNA segments that anneal together with the overlap sequence inside the two primers. This new mutated molecule also contains nicks but at different positions compared with those formed in the first round of PCR that had been "repaired" by overlap extension. Mutations can be introduced successfully by this method. Finally, the circular DNA is transformed into E. coli cells, where the nicks are ligated into a circular plasmid. One important requirement is that the parental plasmid carrying the target gene needs to be methylated by Dam methyltransferase or purified from Dam+ E. coli (i.e., DH5a).

Emergence of Dengue Virus 4 as the Predominant Serotype during the Outbreak of 2017 in South India

AbstractContext: Dengue virus (DENV) causes acute febrile illness in tropical and subtropical countries. In India there is a steady increase in incidence since 1950s which could be attributed to emergence of new serotype or lineage\\clade shifts in circulating DENV. Aims: We aimed to perform molecular characterisation and phylogenetic analysis on samples from the recent outbreak (August–October 2017). Settings and Design: Retrospective epidemiological analysis of dengue outbreak. Subjects and Methods: Samples positive for non-steroidal 1 antigen by enzyme-linked immunosorbent assay (n = 147) were included. The study was approved by our institute ethics committee (JIP/IEC/2018/496). Five hundred and eleven base pair of capsid and pre-membrane encoding genes (CprM) region was amplified using Lanciotti primers, followed by second round of polymerase chain reaction using serotype specific primers. Samples which were positive by second round (n = 68) were sequenced and genotyped using Basic Local Alignment Search Tool analysis and phylogenetic tree was constructed by MEGA7 software. Results: Phylogenetic analysis of CprM sequences identified all 4 serotypes in circulation during this outbreak. We observed both single (n = 50) and concurrent infections (n = 18), with DENV4 as the major contributor (64%). Within Genotype I of DENV4 we observed a distinct new clade (Clade E) which was 2.6% ± 0.9%–5.5% ± 1.1% divergent from the other clades. Among the concurrent infection, DENV 4 and DENV 2 combination was observed to form the majority (77.8%). Conclusions: Overall this study documents the emergence of DENV4 as the major serotype in circulation, replacing DENV1, 2 and 3 which had been previously reported from Tamil Nadu and Puducherry. This substantiates the need for continuous monitoring in endemic countries like India, where such data may impact the formulation of vaccine policy for dengue.

Megaprimer Polymerase Chain Reaction (PCR)-Based Mutagenesis

The megaprimer method is a simple and versatile approach that can be adopted to create a single mutation in a specific target region as well as to create site-specific insertions, deletions, and gene fusions. This method uses three oligonucleotide primers, two rounds of polymerase chain reaction (PCR), and a DNA template containing the gene to be mutated. The first round of PCR generates a fragment with the desired mutation introduced by using one of the flanking primers and the mutant primer. This amplified fragment-the megaprimer-is used in the second PCR along with the remaining external primer to amplify a longer region of the template DNA. The final product is purified and can be cloned into an appropriate vector. By designing flanking primers with universal restriction site sequences, compatible with the vector of choice, it is possible to create different mutant clones by changing only the mutant primer. Recently, this approach has been improved by the use of forward and reverse flanking primers with significantly different melting temperatures. This allows researchers to perform both PCR steps in a single tube. This protocol has been successfully applied on templates with either low or high G + C content to amplify megaprimers 71-800 bp in length and final products ranging from 400 to 2500 bp.

Rapid Amplification of Sequences from the 3′ Ends of mRNAs: 3′-RACE

cDNAs whose first-strand synthesis has been primed by oligo(dT) generally contain the 3' sequences of the RNA. However, cDNAs generated by internal gene-specific primers will usually lack one or both terminal regions of the parental mRNA. And alternate splicing or the presence of an internal A-rich tract can generate cDNA clones that lack 3' sequences. These sequences can be recovered using 3'-RACE (rapid amplification of cDNA ends), which can also be used to map the 3' termini of families of mRNAs with alternative polyadenylation sites. Briefly, a population of mRNAs is transcribed into cDNA using an adaptor-primer with a poly(T) at its 3' end and 30-40 nt containing the recognition sites for two or three restriction enzymes at its 5' end. Reverse transcription is usually followed by two successive rounds of polymerase chain reaction (PCR). The first is primed by a gene-specific sense oligonucleotide and the antisense (dT) adaptor-primer. The products of the first PCR can be used as templates for a second, nested PCR, which is primed by a gene-specific sense oligonucleotide internal to the first, and a second antisense oligonucleotide whose sequence is identical to the central region of the (dT) adaptor-primer. The products amplified in the second PCR are isolated, cleaved with a suitable restriction enzyme, cloned, and characterized.

Detecting the Lyme Disease Spirochete, Borrelia Burgdorferi, in Ticks Using Nested PCR.

Lyme disease is a serious vector-borne infection that is caused by the Borrelia burgdorferi sensu lato family of spirochetes, which are transmitted to humans through the bite of infected Ixodes ticks. The primary etiological agent in North America is Borrelia burgdorferi sensu stricto. As geographic risk regions expand, it is prudent to support robust surveillance programs that can measure tick infection rates, and communicate findings to clinicians, veterinarians, and the general public. The molecular technique of nested polymerase chain reaction (nPCR) has long been used for this purpose, and it remains a central, inexpensive, and robust approach in the detection of Borrelia in both ticks and wildlife. This article demonstrates the application of nPCR to tick DNA extracts to identify infected specimens. Two independent B. burgdorferi targets, genes encoding Flagellin B (FlaB) and Outer surface protein A (OspA), have been used extensively with this technique. The protocol involves tick collection, DNA extraction, and then an initial round of PCR to detect each of the two Borrelia-specific loci. Subsequent polymerase chain reaction (PCR) uses the product of the first reaction as a new template to generate smaller, internal amplification fragments. The nested approach improves upon both the specificity and sensitivity of conventional PCR. A tick is considered positive for the pathogen when inner amplicons from both Borrelia genes can be detected by agarose gel electrophoresis.

Detecting the Lyme Disease Spirochete, &lt;em&gt;Borrelia Burgdorferi&lt;/em&gt;, in Ticks Using Nested PCR

Lyme disease is a serious vector-borne infection that is caused by the Borrelia burgdorferi sensu lato family of spirochetes, which are transmitted to humans through the bite of infected Ixodes ticks. The primary etiological agent in North America is Borrelia burgdorferi sensu stricto. As geographic risk regions expand, it is prudent to support robust surveillance programs that can measure tick infection rates, and communicate findings to clinicians, veterinarians, and the general public. The molecular technique of nested polymerase chain reaction (nPCR) has long been used for this purpose, and it remains a central, inexpensive, and robust approach in the detection of Borrelia in both ticks and wildlife. This article demonstrates the application of nPCR to tick DNA extracts to identify infected specimens. Two independent B. burgdorferi targets, genes encoding Flagellin B (FlaB) and Outer surface protein A (OspA), have been used extensively with this technique. The protocol involves tick collection, DNA extraction, and then an initial round of PCR to detect each of the two Borrelia-specific loci. Subsequent polymerase chain reaction (PCR) uses the product of the first reaction as a new template to generate smaller, internal amplification fragments. The nested approach improves upon both the specificity and sensitivity of conventional PCR. A tick is considered positive for the pathogen when inner amplicons from both Borrelia genes can be detected by agarose gel electrophoresis.

English

Malaria is still a public health problem in the world. It accounted for an estimated 214 million cases and 438,000 deaths in the year 2015. During the dry season, most people are likely to be asymptomatic and therefore fail to be diagnosed with malaria. This study established the proportion of people who came to health facility, escorting sick relatives and had detectable malaria parasites. This was a cross sectional study. All relatives who escorted sick patients to Karume Health Centre between August and December 2013 were screened for malaria using malaria rapid diagnostic test (mRDT) and single round PCR targeting mitochondrial DNA. A total of 400 relatives were screened for malaria using two methods. Prevalence of malaria was 14.5 and 16.8% by mRDT and polymerase chain reaction (PCR), respectively. The prevalence of malaria was higher among febrile patients by methods, mRDT (17.8%) and PCR (17.1%), respectively. The prevalence of asymptomatic malaria was 16.4 and 16.5% by mRDT and PCR, respectively. The overall agreement between the two tests was 87.1% with positive agreement of 63.8% and negative agreement of 91.2%. There were a substantial proportion of patients with malaria who visited the health facilities during the dry season. mRDT and single round PCR targeting mitochondrial DNA had a good agreement and can be used for detection of both symptomatic and asymptomatic malaria. Provider initiated screening can help to improve malaria detection during the dry season, as we move towards reduced malaria prevalence and elimination phase. Key words: Asymptomatic malaria, prevalence of malaria among relatives, mitochondrial DNA, polymerase chain reaction (PCR).

Genetic Testing of the mucin 1 gene-Variable Number Tandem Repeat Single Cytosine Insertion Mutation in a Chinese Family with Medullary Cystic Kidney Disease.

Background:Medullary cystic kidney disease (MCKD) is clinically indistinguishable from several other autosomal-dominant renal diseases; thus, molecular genetic testing is needed to establish a definitive diagnosis. A specific type of single cytosine insertion in the variable number tandem repeat (VNTR) of the mucin 1 (MUC1) gene is the only known cause of MCKD1; however, genetic analysis of this mutation is difficult and not yet offered routinely. To identify the causative mutation/s and establish a definitive diagnosis in a Chinese family with chronic kidney disease, clinical assessments and genetic analysis were performed, including using a modified genotyping method to identify the MUC1-VNTR single cytosine insertion.Methods:Clinical data from three patients in a Chinese family with chronic kidney disease were collected and evaluated. Linkage analysis was used to map the causative locus. Mutation analysis of uromodulin (UMOD) gene was performed using polymerase chain reaction (PCR) and direct sequencing. For MUC1 genotyping, the mutant repeat units were enriched by MwoI restriction, and then were amplified and introduced into pMD-18T vectors. The 192 clones per transformant were picked up and tested by colony PCR and second round of MwoI digestion. Finally, Sanger sequencing was used to confirm the MUC1 mutation.Results:Clinical findings and laboratory results were consistent with a tubulointerstitial lesion. Linkage analysis indicated that the family was compatible with the MCKD1 locus. No mutations were found in UMOD gene. Using the modified MUC1 genotyping method, we detected the MUC1-VNTR single cytosine insertion events in three patients of the family; and mutation-containing clones were 12/192, 14/192, and 5/96, respectively, in the three patients.Conclusions:Clinical and genetic findings could support the MCKD1 diagnosis. The modified strategy has been demonstrated to be a practical way to detect MUC1 mutation.

Cultivation of Entamoeba species in Lock’s -egg medium and differentiation of E.moshkoviskii ,E.dispar and Ehistolytica by using single round polymerase chain reaction

The genus Entamoeba contains many species, three of which are identical (Entamoeba histolytica, Entamoeba dispar and Entamoeba moshkovskii ) reside in the human intestinal lumen. Entamoeba histolytica is the causative agent of amebiasis and mortality worldwide in humans. Although recent studies highlight the recovery of E. dispar andE. moshkovskii from patients with gastrointestinal symptoms. The cultivation of three identical Entamoeba species was done successfully in Lock’s-egg medium , a high number of trophozoite were found in culture .these three identical Entamoeba species did not differentiation by using microscope .but the devolution of scientific they could differentiation by using PCR technique when extraction the DNA in stool samples by using specific bands and primers

A reliable and efficient DNA storage architecture

DNA Storage DNA has the potential to provide large-capacity information storage. However, current methods have only been able to use a fraction of the theoretical maximum. Erlich and Zielinski present a method, DNA Fountain, which approaches the theoretical maximum for information stored per nucleotide. They demonstrated efficient encoding of information—including a full computer operating system—into DNA that could be retrieved at scale after multiple rounds of polymerase chain reaction. Science , this issue p. [950][1] [1]: /lookup/doi/10.1126/science.aaj2038

DNA Fountain enables a robust and efficient storage architecture.

DNA is an attractive medium to store digital information. Here we report a storage strategy, called DNA Fountain, that is highly robust and approaches the information capacity per nucleotide. Using our approach, we stored a full computer operating system, movie, and other files with a total of 2.14 × 106 bytes in DNA oligonucleotides and perfectly retrieved the information from a sequencing coverage equivalent to a single tile of Illumina sequencing. We also tested a process that can allow 2.18 × 1015 retrievals using the original DNA sample and were able to perfectly decode the data. Finally, we explored the limit of our architecture in terms of bytes per molecule and obtained a perfect retrieval from a density of 215 petabytes per gram of DNA, orders of magnitude higher than previous reports.