Comparison of DNA extraction methods for molecular identification of pathogenic Leptospira in the urine samples

Latar belakang: Leptospirosis merupakan zoonosis penting di dunia, yang masih sering terjadi salah diagnosis. Deteksi laboratorium Leptospira menjadi tantangan karena bakterimea cukup singkat untuk dideteksi molekuler, namun antibodi juga muncul sangat lambat. Urine dapat menjadi sampel alternatif untuk deteksi PCR pada leptospirosis. Pengerjaan PCR membutuhkan DNA berkualitas dan andal, dan diperoleh dari metode ekstraksi DNA yang baik. Penelitian bertujuan untuk mengetahui metode ekstraksi DNA Leptospira terbaik untuk sampel urin, serta mengevaluasi pengaruh waktu penyimpanan dan suhu terhadap kestabilan DNA. Metode: Penelitian ini menggunakan tiga metode isolasi DNA yang berbeda; berbasis silika dengan spin kolom, kromatografi spin column menggunakan resin sebagai matriks pemisah, dan metode larutan dengan guanidine isothiocyanate. Hasil ekstraksi diperiksa konsentrasi dan kemurniannya. Gen SecY pada Leptospira dideteksi dengan PCR real-time. Pengaruh suhu dan lama penyimpanan DNA juga dilihat. Hasil: Hasil isolasi DNA menggunakan resin menunjukkan konsentrasi tertinggi (7,94 + 2,11 μg / mL) dan jumlah salinan amplifikasi DNA Leptospira tertinggi (50167,92 + 1,19). Suhu penyimpanan pada suhu 4°C, -20°C, dan -80°C dan umur simpan 91 hari tidak berpengaruh terhadap kualitas dan kuantitas DNA Leptospira hasil isolasi spike urin. Kesimpulan: Isolasi DNA menggunakan spin column chromatography dengan resin sebagai matriks separasi memiliki kualitas dan kuantitas terbaik berdasarkan kemurnian dan konsentrasi DNA serta jumlah gen SecY yang teramplifikasi. Kata kunci: Leptospira, Leptospirosis, ekstraksi DNA, sampel urin, penyimpanan sampel. Abstract Background: Leptospirosis is a worldwide zoonotic disease, which is still often misdiagnosed. Laboratory detection of Leptospira is challenging since the bacteraemia is quite short for molecular detection, however, the rise of the antibody is late to post the infection. Urine can be a potential alternative sample for PCR detection in leptospirosis. The PCR method requires a reliable DNA template, which is obtained from good DNA extracting methods. The study aimed to determine the best method of extraction Leptospira DNA from the urine sample, as well as evaluating the effect of time storage and temperature for its DNA stability. Methods: This study was utilizing three different DNA isolation methods; silica based with spin column, spin column chromatography using resin as separation matrix, and solution method with guanidine isothiocyanate. The yields were examined for its concentration and purity. Leptospira’s SecY gene was detected with realtime PCR. The influences of storage temperature and the life time of the DNA were also studied. Results: The yield of DNA isolation using resin showed the highest concentration (7.94+2.11 μg/mL) and highest Leptospira DNA amplification copy number (50167.92+1.19). Storage temperature at 4°C, -20°C, and -80°C and life time of 91 days did not have any effect on the quality and quatnity of Leptospira DNA isolated from spiked urine. Conclusions: DNA isolation using spin column chromatography with resin as separation matrix has the best quality and quantity based on the purity and concentration of DNA and the higher number of amplified SecY gene. Keywords: Leptospira, Leptospirosis, DNA extraction, urine sample, sample storage

Demonstration of a fast and easy sample-to-answer protocol for tuberculosis screening in point-of-care settings: A proof of concept study

We sought to develop a smooth and low cost sample preparation and DNA extraction protocol, streamlined with a ready-to-use qPCR in a portable instrument to overcome some of the existing hurdles. Several solutions were evaluated as to their ability to liquefy a mucin-based matrix. Each liquefied matrix, supplemented with either Mycobacterium tuberculosis (MTB) H37Rv strain DNA or intact cells, was aliquoted onto a filter paper embedded with solubilizing agents, and was subsequently dried up. Most of the nucleic acids, including genomic DNA from the bacilli and the host, binds to the filter paper. Next, several protocols were evaluated to elute the DNA from the paper, using qPCR to detect the insertion sequence IS6110, a M. tuberculosis complex genomic marker. The limit of detection (LOD) of the best protocol was then evaluated using parallel seeding and colony counting. The protocol was also evaluated using seventeen sputum samples, previously characterized by the GeneXpert or culture. Two instruments (the ABI7500 Standard and the Q3-Plus system) and two reagents storage formats (frozen or ready-to-use) were evaluated. Solutions containing guanidine isothiocyanate exerted the best liquefying effect on the mucin-based matrix extracted from one 6-mm punches, followed by a brief incubation at 95°C. The resulting DNA contained impurities, but a simple 1:10 dilution elicited the detection of MTB and human genomic targets. The described protocol presented an apparent LOD of 02 CFU/mL of MTB. Challenging the protocol with previously characterized samples showed substantial agreement with GeneXpert MTB/RIF results (sensitivity of 90%, agreement of 88.9%, kappa coefficient of 0.77), and moderate agreement with culture results (sensitivity of 100%, agreement of 78.9%, kappa coefficient of 0.58). This work presents a sensitive proof–of-concept protocol for sputum liquefaction and decontamination followed by a simple DNA extraction procedure, in which the extraction steps are streamlined with a ready-to-use qPCR in a portable instrument that can be employed in low infrastructure settings.

EVALUATION OF THREE RNA EXTRACTION METHODS FROM THREE CULTIVARS OF MALAYSIAN UPLAND RICE

Rice (Oryza sativa L.) can be divided into two major categories, which is upland rice and lowland rice. Apart from being the staple food for more than half of the world population, it is also known as model plant for functional genomics study. However, it possess high amount of starch and polysaccharide that makes the isolation of good quality RNA for downstream purposes often a difficult task. While there are many studies being carried out for lowland rice extraction, none has been reported for upland rice. This study is the first to report on evaluation of three RNA extraction methods for three Malaysian upland rice cultivars in order to determine the best method to isolate high grade RNA. The result obtained demonstrated that good quality RNA in terms of integrity, purity and quality can be isolated from young leaves of these cultivars by using guanidine isothiocyanate based extraction method that is fast, simple and efficient and had been proven suitable for further downstream applications.

Two sequential PCR amplifications for detection of Schistosoma mansoni in stool samples with low parasite load

Schistosomiasis constitutes a major public health problem, with an estimated 200 million individuals infected worldwide and 700 million people living in risk areas. In Brazil there are areas of high, medium and low endemicity. Studies have shown that in endemic areas with a low prevalence of Schistosoma infection the sensitivity of parasitological methods is clearly reduced. Consequently diagnosis is often impeded due to the presence of false-negative results. The aim of this study is to present the PCR reamplification (Re-PCR) protocol for the detection of Schistosoma mansoni in samples with low parasite load (with less than 100 eggs per gram (epg) of feces). Three methods were used for the lysis of the envelopes of the S. mansoni eggs and two techniques of DNA extraction were carried out. Extracted DNA was quantified, and the results suggested that the extraction technique, which mixed glass beads with a guanidine isothiocyanate/phenol/chloroform (GT) solution, produced good results. PCR reamplification was conducted and detection sensitivity was found to be five eggs per 500 mg of artificially marked feces. The results achieved using these methods suggest that they are potentially viable for the detection of Schistosoma infection with low parasite load.

How the RNA isolation method can affect microRNA microarray results.

The quality of RNA is crucial in gene expression experiments. RNA degradation interferes in the measurement of gene expression, and in this context, microRNA quantification can lead to an incorrect estimation. In the present study, two different RNA isolation methods were used to perform microRNA microarray analysis on porcine brain tissue. One method is a phenol-guanidine isothiocyanate-based procedure that permits isolation of total RNA. The second method, miRVana™ microRNA isolation, is column based and recovers the small RNA fraction alone. We found that microarray analyses give different results that depend on the RNA fraction used, in particular because some microRNAs appear very sensitive to the RNA isolation method. We conclude that precautions need to be taken when comparing microarray studies based on RNA isolated with different methods.

Polymerase chain reaction for the diagnosis of bovine genital campylobacteriosis

Bovine genital campylobacteriosis is a common venereal disease of cattle; the prevalence of this disease can be underestimated mostly because of the nature of the etiological agent, the microaerobic Campylobacter fetus subspecies venerealis. The purpose of the current study was to evaluate the utilization of polymerase chain reaction (PCR) in the diagnosis of genital campylobacteriosis in samples obtained from bull prepuce aspirate, cow cervical mucus, and abomasum contents of aborted fetuses, collected into enrichment medium. Five different DNA extraction protocols were tested: thermal extraction, lysis with proteinase K, lysis with guanidine isothiocyanate, lysis with DNAzol, and lysis with hexadecyltrimethylammonium bromide (CTAB). The specificity, sensitivity, and technical application of the PCR assay were also evaluated with clinical samples and compared to bacterial isolation by standard culture. DNA extraction by the CTAB protocol provided better results in PCR, and it was able to detect 63 colony-forming units per ml of C. fetus. Out of 277 clinical samples tested, 68 (24%) were positive for Campylobacter fetus using PCR, while only 8 (2.8%) of the samples were positive by bacterial isolation in solid medium, proving the superiority of the PCR technique when compared to the standard isolation method, and providing evidence for its usefulness as a better screening test in cattle for the diagnosis of bovine genital campylobacteriosis.

Isolation of Quality Total RNA from the Aromatic Plant Origanum onites

We successfully used the guanidine isothiocyanate method for isolation of total RNA from leaf, stem, and root tissues of the aromatic plant Origanum onites. The RNA was extracted with TRI Reagent® at room temperature and was recovered by isopropanol precipitation. The isolated RNA was capable of reverse transcription. The extraction method described here does not require ultracentrifugation, and it is fast, simple, and effective. The procedure can be completed within 3 hours and may be applicable to other aromatic medicinal plants containing high amounts of phenolic compounds.