The diagnostic values of multicolor melting curve analysis on drug resistance to 5 anti-tuberculosis drugs / 中国热带医学

@#Abstract: Objective To explore and analyze the diagnostic value of multicolor melting curve analysis (MMCA) for the resistance of five anti-tuberculosis drugs, so as to clarify the clinical value of MMCA in detecting drug resistance of Mycobacterium tuberculosis. Methods From April 2021 to May 2022, 200 patients with positive Mycobacterium tuberculosis admitted to the Fourth People's Hospital of Qinghai Province were selected as research objects, and sputum specimens were taken from the patients. Traditional Mycobacterium tuberculosis drug sensitivity test (modified Löwenstein-Jensen medium method) and MMCA analysis were respectively given to detect the resistance of five anti-tuberculosis drugs, including isoniazid, ethambutol, streptomycin, rifampicin and isoniazid, respectively. Those samples with inconsistent results between the two diagnosis methods were subjected to gene sequencing verification, and the diagnosis efficiency of MMCA for the five anti-tuberculosis drugs was compared. Results Using Mycobacterium tuberculosis drug sensitivity as the gold standard for drug resistance diagnosis, the sensitivity of MMCA for detecting drug resistance of rifampicin, ethambutol, streptomycin, isoniazid and levofloxacin were 95.83% (46/48), 93.75% (15/16), 100.00% (15/15), 100.00% (20/20) and 70.00% (7/10), respectively, with statistical differences between groups (P<0.05). There were no statistically significant differences in the specificity, positive predictive value, negative predictive value and accuracy of MMCA for the five anti-tuberculosis drugs (P>0.05). For the 8 samples with inconsistent results between MMCA and modified Löwenstein-Jensen medium method, gene sequencing was performed and compared with the results of gene sequencing. After comparison with gene sequencing results, it was found that the coincidence rate of MMCA and gene sequencing results was 75.00% (6/8). Conclusions In the detection of drug-resistant mutations in TB patients, multi-color probe fusion curve analysis has high diagnostic efficacy for first-line anti-tuberculosis drugs, but is not sensitive to second-line anti-tuberculosis drug levofloxacin. Therefore, for the detection of first-line anti-tuberculosis drugs, MMCA has a good clinical application prospect.

The clinical value of fluorescence quantitative assay and G6PD/6PGD ratio method in the diagnosis of glucose-6-phosphate dehydrogenase deficiency and gene mutation / 中华检验医学杂志

Objective:To investigate the diagnostic value of fluorescence quantitative method and G6PD/6PGD ratio method in glucose-6-phosphate dehydrogenase (G6PD) deficiency and the type of gene mutation.Methods:A total of 1 201 patients (711 males and 490 females) with suspected G6PD deficiency in Shanghai Children′s Hospital were collected from June 2018 to March 2021. Fluorescence quantification method, G6PD/6PGD ratio method and multicolor melting curve were used to detects enzyme activity, ratio and gene mutation type. Comparison of each index and evaluation of its diagnostic efficiency were performed.Results:Among 1 201 suspicious samples, 163 cases (135 males and 28 females) were finally diagnosed. 156 cases were diagnosed by fluorescence quantitative method with a detection rate of 95.71%, and 140 cases were diagnosed by G6PD/6PGD ratio method with a detection rate of 85.89%. enzymatic activity of G6PD and ratio of G6PD/6PGD in male were significantly lower than female, and the differences were statistically significant ( U=642.5, 734.5, P<0.001). 112 cases received G6PD gene mutation detection and 92 cases were diagnosed, 74 were hemizygous mutations, 1 were homozygous mutations, 15 were heterozygous mutations, and 2 were compound heterozygous mutations. Among 15 cases of heterozygous mutations, 11 cases were diagnosed by fluorescence quantitative method, the diagnosed rate was 73.33%, 4 cases were diagnosed by G6PD/6PGD ratio method, and the diagnosed rate was 26.67%. A total of 7 mutation sites were detected and the proportions were c.1388G>A (32.22%), c.1376G>T (30.00%), c.871G>A (13.33%), c.1024C>T (11.11%). c.95A>G (7.78%), c.487G>A (4.44%), c.392G>T (1.11%). The enzymatic activities of c.1376G>T and c.1024C>T, c.487G>A were statistically significant ( P<0.001,0.015); the G6PD/6PGD ratios of c.1024C>T and c.1388G>A, c.1376G>T were statistically significant ( P=0.017,0.002,0.011,0.013). Fluorescence quantitative method had sensitivity of 100%, specificity of 95.65%, and the area under the curve (AUC) is 0.972. The sensitivity of the G6PD/6PGD ratio method was 100%, the specificity was 94.57%, and the AUC was 0.979. The sensitivity of fluorescence quantitative method combined with G6PD/6PGD ratio was 96.7%, the specificity was 100%, and the AUC was 0.992. Conclusions:Compared with fluorescence quantification, the G6PD/6PGD ratio method might not be able to diagnose female heterozygotes effectively; The panel of G6PD fluorescence quantification and G6PD/6PGD ratio was helpful to reduce the missed diagnosis. Combined with gene mutation analysis, it could improve the diagnosis rate of G6PD deficiency in the children.

Detection of the Brachyspina mutation in Uruguayan Holstein cows using real time PCR and melting curve analysis / Detecção da mutação da Brachyspina em vacas Holandês Uruguaias usando PCR em tempo real e análise da curva de fusão

ABSTRACT: Brachyspina syndrome (BS) is a rare monogenic autosomal recessive hereditary disorder of the Holstein Fresian breed caused by a deletion of 3.3Kb in the Fanconi anemia complementation group I (FANCI) gene on BTA-21, which leads to a frame-shift and premature stop codon. Some of the consequences of BS are the reduction of the fertility rate and milk production. This study developed a simple, sensitive, rapid cost- effective assay method based on real time PCR and melting curve analysis for the detection of BS carrier animals. Sixty-eight normal homozygous and four heterozygous carrier genotypes were detected and confirmed through traditional PCR- electrophoresis analysis. We concluded that the assay we have developed proved to be a reliable, highly precise and low-cost tool, which could be used to monitor the presence of the BS mutation in uruguayan Holstein breed.

RESUMO: A síndrome de Brachyspina (BS) é um defeito hereditário monogênico autossômico recessivo raro da raça Holstein Friesian causado por uma exclusão de 3,3 KB no gene FANCI localizado no cromossomo bovino 21, o que leva a um deslocamento de quadro e um códon de parada prematuro. Uma consequência da BS é a eficiência de reprodução reduzida e a produção de leite. O objetivo deste estudo foi o desenvolvimento de um método simples, rápido e sensível, baseado em PCR em tempo real e análise da curva de fusão para identificar animais portadores de BS. Sessenta e oito genótipos homozigotos normais e quatro heterozigotos foram detectados e confirmados através da análise tradicional de PCR e electophorese. Concluímos que o novo método é uma ferramenta confiável, altamente precisa e de baixo custo, que poderia ser usado para monitorar a presença da mutação BS na raça Holandês uruguaia.

Performance evaluation of the automated SNPs analyzer for the detection of JAK2 V617F mutation / 中华检验医学杂志

Objective To test and evaluate the JAK2 gene V617F mutation in patients with myeloproliferative tumors based on i-densy IS-5320 platform according to ISO15189 accreditation requirements.Methods Instrument performance verification.Selected from December 2014 to February 2017, 20 cases of JAK2 V617F mutation positive peripheral blood samples from Huashan Hospital of the Shanghai FuDan University Medical College and 20 cases of peripheral blood samples with negative JAK2V617F mutation.The Realtime PCR with TaqMan MGB probe was selected as the control method to verify and evaluate the accuracy of testing JAK 2 V617F mutation on i-densy IS-5320 platform.Whole blood samples were used to evaluate the reproducibility , cross-contamination and anti-interference ability of this platform.The ability of mutation load was verified by detecting mixtures of human erythnoleukemia cells and colorectal cancer cell HCT116 with 12 different proportions.Results I-densy IS-5320 platform and TaqMan MGB probe real-time fluorescence quantitative PCR show the same result .The within-run reproducibility and between-run reproducibility are both 100%.There is no observed contamination .High bilirubin and high triglyceride blood samples have no obvious interference on mutation detection .The mutation ratio with a load as low as 0.25%could be tested stably by i-densy IS-5320 platform.The detecting peak of melting curve can reflect the ratio of JAK2 V617F mutation to some extent.Conclusions I-densy IS-5320 can detect the mutation of JAK2 V617F gene in the whole blood directly.It has high sensitivity, accuracy and stability, and is easy to operate, and also can reflect the mutation load of JAK2 V617F, which could meet the clinical requirements for the detection of mutations.

Genotypic Identification of Cystoisospora in Immunocompromised Patients Using T(m)-Variation Analysis

Cystoisospora is responsible for morbidity in immunocompromised patients. PCR is sensitive for diagnosing Cystoisospora; however, it needs reevaluation for differential molecular diagnosis of cystoisosporiasis. We aimed at evaluating melting curve analysis (MCA) after real-time PCR (qPCR) in diagnosis and genotyping of Cystoisospora as an alternative to conventional PCR. We included 293 diarrheic stool samples of patients attending the Department of Clinical Oncology and Nuclear Medicine of Cairo University Hospitals, Egypt. Samples were subjected to microscopy, nested PCR (nPCR), and qPCR targeting the internal transcribed spacer 2 region (ITS2) of the ribosomal RNA (r RNA) gene followed by melting temperatures (T(m)s) analysis and comparing the results to PCR-RFLP banding patterns. Using microscopy and ITS2-nPCR, 3.1% and 5.8% of cases were Cystoisospora positive, respectively, while 10.9% were positive using qPCR. Genotyping of Cystoisospora by qPCR-MCA revealed 2 genotypes. These genotypes matched with 2 distinct melting peaks with specified T(m)s at 85.8°C and 88.6°C, which indicated genetic variation among Cystoisospora isolates in Egypt. Genotype II proved to be more prevalent (65.6%). HIV-related Kaposi sarcoma and leukemic patients harbored both genotypes with a tendency to genotype II. Genotype I was more prevalent in lymphomas and mammary gland tumors while colorectal and hepatocellular tumors harbored genotype II suggesting that this genotype might be responsible for the development of cystoisosporiasis in immunocompromised patients. Direct reliable identification and differentiation of Cystoisospora species could be established using qPCR-T(m)s analysis which is useful for rapid detection and screening of Cystoisospora genotypes principally in high risk groups.

The correlation between the apolipoprotein E genetic polymorphisms and sepsis in children / 中华急诊医学杂志

Objective To study the correlation between apolipoprotein E (APOE) genetic polymorphisms and sepsis in Chinese children.Methods The inpatients suffered with sepsis were enrolled as septic group and the healthy children from child health division were enrolled as control group.The study of APOE genotypes were carried out by polymerase chain reactions followed a high-resolution melting curve analysis.SPSS 16.0 statistical software was used for data analysis.Mann-Whitney U test was used to compare the age between the groups.Hardy-Weinberg equilibrium was tested using the Pearson x2-test.The x2-test was used to compare gender and the genotype distribution between the groups.The odd ratio (OR) was calculated together with its 95％ confidence interval (CI).Potential confounding effects of variables were corrected using a multivariate unconditional logistic regression model.All statistical tests were two-sided and P ＜ 0.05 indicates statistically significance.Results Among a total of 285 children collected from March 2011 to June 2012,there were 88 patients with sepsis and 197 healthy children.In the septic group,15 septic patients were complicated with central nervous system infection.Four apolipoprotein E genotypes were identified to be ε3/ε3,ε2/ε3,ε3/ε4,and ε2/ε4.The percentage of each genotype found in patients of the septic group and the control group was 64.4％ vs.73.1％ (ε3/ε3);16.8％ vs.10.7％ (ε2/ε3);18.8％ vs.14.7％ (ε3/ε4);0％ vs.1.5％ (ε2/ε4),respectively.The number of patients with the genotype ε3/ε3 among septic patients was significantly lower than that among the control individuals (P =0.047,1-β =0.334,OR =0.585,adjusted OR =0.559).The number of patients with the genotype ε3/ε3 among the septic patients with central nervous system infection was 33.3％,which was also significantly lower than that among the septic patients without CNS infection (67.1％).(P =0.014,1-β5 =0.685,OR =0.245,adjusted OR =0.275).Conclusions Apolipoprotein E genetic polymorphisms were associated with the occurrence of sepsis and central nervous system complications in children.The susceptibility of children with genotype ε3/ε3 to sepsis and central nerve system infection complications is significantly lower than that of children with other genotypes.

Probe melting curve analysis-based PCR assay for the rapid detection of non-deletionα-thalassemia(αT) / 国际检验医学杂志

Objective To investigate the clinical value of the probe melting curve analysis‐based PCR assay for the detection of three types of αT .Methods A total of 149 blood and prenatal archival DNA samples (6 of which were amniotic fluid samples)with three knownαT genes ,which included 63 carriers with Hb CS ,22 cases with Hb QS ,43 individuals with Hb WS and 1 double heter‐ozygote with Hb CS and Hb WS) as well as 20 samples with normalα‐globin gene sequence that had been confirmed by RBD com‐bined with DNA sequencing were selected to test the specificity of probe melting curve analysis by blind analysis .Results The probe melting curve analysis accurately detected 100 of the DNA samples previously characterized by S RBD combined with DNA sequencing .Conclusion Probe melting curve analysis‐based PCR assay for the detection ofαT is featured with rapidity and accuracy and can be applied to clinical and prenatal diagnosis .

Rapid screening of rpoB and katG mutations in Mycobacterium tuberculosis isolates by high-resolution melting curve analysis.

Background: Early detection of multidrug‑resistant tuberculosis (MDR‑TB) is essential to prevent its transmission in the community and initiate effective anti‑TB treatment regimen. Materials and Methods: High‑resolution melting curve (HRM) analysis was evaluated for rapid detection of resistance conferring mutations in rpoB and katG genes. We screened 95 Mycobacterium tuberculosis clinical isolates including 20 rifampin resistant (RIF‑R), 21 isoniazid resistant (INH‑R) and 54 fully susceptible (S) isolates determined by proportion method of drug susceptibility testing. Nineteen M. tuberculosis isolates with known drug susceptibility genotypes were used as references for the assay validation. The nucleotide sequences of the target regions rpoB and katG genes were determined to investigate the frequency and type of mutations and to confirm HRM results. Results: HRM analysis of a 129‑bp fragment of rpoB allowed correct identification of 19 of the 20 phenotypically RIF‑R and all RIF‑S isolates. All INH‑S isolates generated wild‑type HRM curves and 18 out of 21 INH‑R isolates harboured any mutation in 109‑bp fragment of katG exhibited mutant type HRM curves. However, 1 RIF‑R and 3 INH‑R isolates were falsely identified as susceptible which were confirmed for having no mutation in their target regions by sequencing. The main mutations involved in RIF and INH resistance were found at codons rpoB531 (60% of RIF‑R isolates) and katG315 (85.7% of INH‑R isolates), respectively. Conclusion: HRM was found to be a reliable, rapid and low cost method to characterise drug susceptibility of clinical TB isolates in resource‑limited settings.

A study of rapid genotyping method for methicillin-resistant Staphylococcus aureus / 国际检验医学杂志

Objective To establish a rapid genotyping method of for methicillin-resistant Staphylococcus aureus(MRSA) based on polymerase chain reaction(PCR)-high resolution melting (HRM ) curve analysis and staphylococcal protein A (SPA ) classifica-tion .Methods 71 strains of MRSA clinically isolated were collected as test strains .Gene sequencing and HRM curve analysis were employed to conduct SPA gene typing .Results According to gene sequencing method ,SPA gene of 71 strains of MRSA was divided into four types ,namely t570 ,t030 ,t002 and t588 .The most predominant type was t570 (74 .65% ) ,followed by t030 and t002(both 7 cases) .The result of SPA gene typing by HRM analysis were basically consistent with that by gene sequencing .Con-clusion PCR-HRM analysis is expected to become a fast ,efficient genotyping for MRSA SPA gene ,providing the basis for hospital infection control .

Melting curve aaalysis for the screening of heptitis b virus genotypes a, d annd f in patients from a general hospital in southern Brazil / Analise da curva de melting para o screening dos genotipos A, D e F do virus da hepatite B em pacientes de um hospital geral do sul do Brasil.

Context Hepatitis B virus (HBV) can cause fulminant hepatitis, cirrhosis and hepatocellular carcinoma, and is one of the most common causes of acute and chronic liver failure. The genetic variants of HBV can be decisive for the evolution of these diseases as well as for the election of therapy. Objectives The aim of this study was to evaluate and standardize an in house methodology based on the analysis of the melting curve polymerase chain reaction (PCR) of real-time (qPCR) to screen for genotypes A, D and F of HBV in patients from a hospital in Rio Grande do Sul, Brazil. Methods We evaluated 104 patients presumably with HBV chronic infection. Viral DNA was extracted from plasma and viral genotypes and different mutations were determined using PCR-based protocols. Results A PCR-based methodology was standardized for the analysis of genotypes A, D and F of HBV. The technique was based in a nested PCR with the final step consisting of a multiplex real-time PCR, using the melting curve as a tool for the differentiation of fragments. A higher frequency of genotype D (44.4%), followed by genotype A (22.2%) and genotype F (3.7%) was observed. Conclusion The standardized assay, a nested PCR-multiplex qPCR using specific primers, provides a rapid and accurate method for the differentiation of HBV genotypes that are more frequent in Southern Brazil – A, D and F. This method can be applied in the clinical practice. .

Contexto O vírus da hepatite B pode causar hepatite fulminante, cirrose e carcinoma hepatocelular, sendo uma das causas mais frequentes de doença aguda e crônica do fígado. As variantes genéticas do VHB podem ser determinantes para a evolução da doenças assim como para a eleição da terapêutica. Objetivos O objetivo deste estudo foi padronizar e avaliar uma metodologia “in house”, através da utilização da curva de melting de reação em cadeia da polimerase (PCR) em tempo real (qPCR), como rastreamento para análise dos genótipos A, D e F do vírus da hepatite B em pacientes do Rio Grande do Sul. Métodos Foram avaliados 104 pacientes supostamente com infecção crônica pelo VHB. O DNA foi extraído com kit comercial, os genótipos e as mutações foram determinados utilizando diferentes protolocos baseados em PCR. Resultados Foi padronizada uma metodologia baseada em PCR para a análise dos genótipos A, D e F do VHB. A técnica consistiu de uma PCR Nested incluindo uma etapa final de PCR em tempo real Multiplex, utilizando a curva de melting como ferramenta para a definição dos fragmentos. Foi observada uma maior frequência do genótipo D (44,4%), seguido do genótipo A (22,2%) e do genótipo F (3,7%) na amostra analisada. Conclusão O ensaio padronizado fornece um método rápido e preciso para diferenciar genótipos do VHB mais frequentes no sul do Brasil – A, D e F – usando um PCR Nested Multiplex com primers específicos, o qual apresenta potencial aplicação na prática clínica. .

Excised radicle tips as a source of genomic DNA for PCR-based genotyping and melting curve analysis in cotton.

Genomic DNA isolation in cotton is complicated because of the presence of secondary metabolites that are inhibitory to PCR amplification. We report here that radicle tips, but not other parts of cotton seedlings, yield high-quality DNA that is readily amenable for PCR. The radicle-tip-excised seedlings retain viability because of the formation of adventitious roots. We demonstrate the utility of this method in distinguishing homozygotes from heterozygotes in a cotton breeding population and in hybrid seed purity testing.

Application of high resolution melting analysis in detecting IDH1 mutation in glioma patients / 中国基层医药

Objective To evaluate the feasibility of detecting the mutation of IDH1 in glioma patients by high resolution melting(HRM) curve analysis.Methods The gene mutation of IDH1 was detected by HRM method in 9 surgical resection paraffin specimens of glioma,and the result was verified by gene sequencing.Results 6 cases of R132H(CGT ＞ CAT) mutation and 1 case of R132C(CGT ＞ TGT) mutation were found by HRM method.The resluts of direct gene sequencing were consistent with HRM method.Conclusion The HRM method in detecting IDH1 mutation is more efficient and convenient than direct sequencing.Moreover,it has advantages of low-cost and suitable for clinical test.

Comparison between probe melting curve analysis based on real-time fluorescent PCR and reverse dot blot assay for gene and prenatal diagnosis of β-thalassemia / 中华检验医学杂志

ObjectiveTo evaluate the reliability of the probe melting curve analysis (PMCA) based on real-time fluorescent PCR assay for the genetic diagnosis and prenatal diagnosis of β-thalassemia.MethodsA total of 135 cases of peripheral blood samples were collected from Zhuhai Municipal Maternity and Child Healthcare Hospital between 2008 and 2010.All the samples were performed preliminary diagnosis according to the hematological data.Of these,119 cases were diagnosed as β-thalassemia trait,4 cases were diagnosed as severe thalassemia and 12 cases were normal.In addition,44 cases of amniotic fluid and 8 cases of cord blood with high-risk for severe β-thalassemia were also collected.The diagnostic reliability of the PMCA assay and reverse dot blot assay was evaluated on 187 above-mentioned cases by direct DNA sequencing analysis in a double-blind study.ResultsThe genotypes of 185 cases were detected accurately based on the PMCA assay except for two cases:one heterozygote with Ini( ATG ＞ AGG) was omitted and another heterozygote couldn't be distinguished between CD43 ( G ＞ T) and CD37 ( G ＞ A ).For the RDB assay,only one heterozygote with CD71-72 ( + T) was not detected accurately in the above-mentioned cases.Compared with the DNA sequencing analysis,the sensitivity,specificity,negative predictive value,positive predictive value and diagnostic efficiency of the PMCA assay were 98.75％,100.00％,93.10％,100.00％ and 98.93％,respectively.The corresponding value of the RDB assay were 99.38％,100.00％,96.42％,100.00％ and 99.47％,respectively.There were no significant between-group differences in the diagnostic efficiency of the two assays ( P ＞ 0.05 ).The results of prenatal diagnosis were in complete concordance with the follow up results,after the birth or induced labour of the fetuses.ConclusionsThe PMCA assay can be used as an alternative and verified method of RDB assay for the genetic diagnosis and prenatal diagnosis of β-thalassemia.

The evaluation of a melting curve analysis-based PCR assay for the clinical genetic diagnosis and prenatal diagnosis of β-thalassemia / 中华检验医学杂志

ObjectivesTo investigate the clinical value of the melting curve analysis-based PCR assay for the clinical genetic diagnosis and prenatal diagnosis of β-thalassemia.Methods A total of 451 peripheral blood samples,including 372 cases with β-thalassemia phenotypes and 79 cases without β-thalassemia phenotypes,were collected by Liuzhou Municipal Maternity and Child Healthcare Hospital between January 2011 and August 2011.Moreover,another 84 cases,including 16 fetal villi samples (10 - 13 weeks),64 amniotic fluid samples (16 -24 weeks ) and 4 umbilical cord blood samples (above 17 weeks),whose parents were β-thalassemia carriers,were also collected for this assay between June 2011 and September 2011.A double-blind test was done to compare the detection reliability of the melting curve analysis-based assay (24 β-thalassemia mutations can be detected) with PCR-RDB probe assay (17 β-thalassemia mutations can be detected ) and DNA sequencing using these samples.The wildtype,mutant and total concordance rates of the genotyping results were calculated separately among the melting curve analysis based assay,PCR-RDB probe assay and DNA sequencing.Results Among the 451 peripheral blood samples,thirteen mutations and nineteen genotypes were obtained by using melting curve analysis-based assay.447 samples had the same detection results and 4 samples had different detection results by comparing melting curve analysis-based assay with PCR-RDB probe assay,thus,the concordance rate of the sample detection result was 99.1％ (447/451),and the concordance rate of the allele detection result was 99.6％ (898/902).DNA sequencing results of the 4 samples showed that 3 samples had the same genotyping result with melting curve analysis-based assay,and 1 sample had the same genotyping result with PCR-RDB probe assay.A rare β-globin mutation which was not included by melting curve analysis-based assay was not detected.Thus,the genotypes of 450 samples were detected accurately by melting curve analysis-based assay,and the concordance rate of the sample detection between the melting curve assay and DNA sequencing assay was 99.8％ (450/451).Among 84 fetal villi,amniotic fluid,and umbilical cord blood samples,8 mutation types and 18 genotypes were obtained by using melting curve analysis-based assay.All the samples have the same detection results by comparing melting curve analysis-based assay with PCR-RDB probe assay and DNA sequencing,so the concordance rate of the genotyping results was 100％ among the melting curve analysis-based assay,PCR-RDB probe assay and DNA sequencing.Conclusions The melting curve analysis-based PCR assay can detect multiple unknown samples simultaneously,and detect multiple mutations accurately.It is very useful for the genetic diagnosis and prenatal diagnosis of β-thalassemia.

Detection of Vancomycin-resistant Enterococci using Multiplex Real-time PCR Assay and Melting Curve Analysis / 대한진단검사의학회지

BACKGROUND: We developed and evaluated the utility of a multiplex real-time PCR assay that uses melting curve analysis and allows simultaneous identification of vancomycin-resistant genotypes and clinically relevant enterococci. METHODS: The specificity of the assay was tested using 4 reference strains of vancomycin-resistant enterococci (VRE) and 2 reference strains of vancomycin-susceptible enterococci. Ninety-three clinical isolates of enterococci with different glycopeptide-resistant phenotypes were genotyped and identified using a multiplex real-time PCR assay and melting curve analysis. RESULTS: Representative melting curves were obtained for Enterococcus faecium, Enterococcus faecalis, vanA-containing E. faecium, vanB-containing E. faecalis, Enterococcus gallinarum, and Enterococcus casseliflavus. Phenotypic and genotypic analysis of the isolates revealed same results for 82 enterococcal isolates, while in 4 isolates, the glycopeptide-resistant phenotypes were inconsistent with the glycopeptide-resistant genotypes and in the 4 other isolates, species could not be accurately identified. Three isolates with mixed strains, which were detected by the PCR assay, could not be correctly identified using phenotypic methods. CONCLUSIONS: VRE genotyping and identification of clinically relevant enterococci were rapidly and correctly performed using multiplex real-time PCR assay and melting curve analysis.

Usefulness of Multiplex Real-Time PCR and Melting Curve Analysis in Identification of Nontuberculous Mycobacteria / 대한진단검사의학회지

BACKGROUND: Nontuberculous mycobacteria (NTM) should be correctly identified to the species level, because of different treatment plans among NTM species. This study was performed to assess the usefulness of real-time PCR and melting curve analysis in the identification of NTM. METHODS: One hundred fifty-two clinical NTM isolates were identified to the species level by PCR-restriction fragment length polymorphism analysis (PRA). Those strains were then identified by multiplex real-time PCR and melting curve analysis on the 16S rRNA gene and hsp65 gene. RESULTS: In the 16S rRNA gene fragment analysis, M. abscessus-M. chelonae group showed melting point at temperatures above 65 degrees C and M. avium complex (MAC; M. avium and M. intracelluare) below 48 degrees C, which differentiated M. abscessus-M. chelonae group and MAC from other NTM. In the hsp65 gene fragment analysis, M. abscessus-M. chelonae group was clearly divided into M. abscessus type I, M. abscessus type II, and M. chelonae according to the melting points at 61.25 degrees C, 66.06 degrees C, and 57.58 degrees C, respectively. CONCLUSIONS: With the multiplex real-time PCR and melting curve analysis of 16S rRNA and hsp65 genes, M. abscessus and M. chelonae were readily identified and MAC were differentiated from other NTM. Especially, M. abscessus and M. chelonae, which were not differentiated from each other with the 16S rRNA gene fragment analysis, were identified with hsp65 gene fragment analysis.

Rapid detection of GSTM1 polymorphisms using SYBR green I and melting curve analysis / 临床检验杂志

Objective To establish a method to detect the glutathione stransferase(GST) M1 gene polymorphisms rapidly and to apply preliminary for detection.Methods GSTM1 gene and internal control gene CYP1A1 were amplified by multi-PCR with appropriate fluorescent dye SYBR green I in the reaction system,The changes of fluorescence values were recorded from 65 ℃ to 95 ℃ by a rate of(0.1 ℃/s) when PCR was just completed.Results There were two peaks in the melting curve of GSTM1~+ genotype,but only a single peak occurred for the GSTM1-genotype.The temperatures of two peaks corresponded to the expected Tm.agarose gel electrophoresis analysis demonstrated that these peaks correspond to the bands of the predicted molecular size.The detection can be completed within an hour after DNA was extracted.Conclusion Melting curve analysis combined with SYBR green I is a easy,rapid,accurate methodfor detection of GSTM1 gene polymorphisms.