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 establishment of a high-resolution melting curve genotyping method for ABCG2*376T allele of Jr(a-) and its distribution frequency study / 中国输血杂志

【Objective】 To establish a high-throughput detection method for ABCG2*376T allele of Jr(a-), and apply it to the study of the frequency of this allele in the Chinese population. 【Methods】 The specific primers were designed and synthesized, the sample carrying homozygous ABCG2*376T alleles, obtained in the previous study, was used as the homozygous positive control, and the sample carrying heterozygous allele as the heterozygous positive control. The wild-type sample was used as a negative control, and a high-resolution melting curve(HRM) method for detecting this allele was established. The established method was used to screen DNA samples from blood donors in Guangzhou, and the samples carrying ABCG2*376T alleles were sequenced to confirm the accuracy of the HRM method. 【Results】 A HRM method, which can detect ABCG2*376T allele and accurately type homozygotes and heterozygotes at the same time, had been established successfully. Fifteen individuals with heterozygous alleles were screened out of 1 560 blood donors in Guangzhou, while none homozygous allele was detected. 【Conclusion】 The HRM method can be used to accurately screen and type ABCG2*376T allele. The frequency of this allele in Chinese population is about 0.48%(15/3120).

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.

Fluorescence PCR Amplification Related Technology / 中国生物化学与分子生物学报

Using fluorescence PCR (FPCR) technology to amplify DNA is an important part of modern biological research. The paper traced the invention of FPCR, through its main development, respective principles, design techniques, through to practical applications, etc. The two generations of phased methods of real-time quantitative PCR (QPCR) and digital PCR (DPCR) were mainly reviewed. QPCR that contained means of dyes, hydrolysis probe and its derivatives, hybridization probe containing molecular beacon and Yin-Yang probes, etc, dye melting curve and probe melting curve was summarized. DPCR involving chip digital PCR(cdPCR) and droplet digital PCR (ddPCR) was also included. Furthermore, the main application areas and limitation of FPCR, their characteristics of different types and future development direction were described.

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.

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.

Verification application of PCR techniques with different principles in prenatal diagnosis of thalassemia / 实用医学杂志

Objective To evaluate the necessity and feasibility by using two different PCR-based techniques for prenatal diagnosis of thalassemia. Methods 509 specimens for prenatal diagnosis of thalassemia were detected respectively by single tube multiplex PCR(STMP),reverse dot blot(RDB)or probe melting curve assay(PMCA)for commonα-thalassemia orβ-thalassemia mutations in double-blind tests. Samples with different detection results were confirmed with DNA sequencing analysis. Prenatal diagnosis of thalassemia results were verified or followed up after birth. Results In detectingα-thalassemia andβ-thalassemia,there was one case in STMP + RDB and another case PMCA indicating differentiating results. The detection sensitivity of STMP + RDB was higher than that of PMCA,and its difference can be used as an indication for maternal blood contamination. Conclusion The two PCR methods with different principles were necessary and feasible for the prenatal diagnosis of thalassemia. The two methods were complementary to each other ,which can ensure the reliability of the prenatal diagnosis results and reduce the defects of single technique. It is worthy to be popularized in clinical application.

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.

Investigation of FANCA gene in Fanconi anaemia patients in Iran.

Background & objectives: Fanconi anaemia (FA) is a syndrome with a predisposition to bone marrow failure, congenital anomalies and malignancies. It is characterized by cellular hypersensitivity to cross-linking agents such as mitomycin C (MMC). In the present study, a new approach was selected to investigate FANCA (Fanconi anaemia complementation group A) gene in patients clinically diagnosed with cellular hypersensitivity to DNA cross-linking agent MMC. Methods: Chromosomal breakage analysis was performed to prove the diagnosis of Fanconi anaemia in 318 families. Of these, 70 families had a positive result. Forty families agreed to molecular genetic testing. In total, there were 27 patients with unknown complementary types. Genomic DNA was extracted and total RNA was isolated from fresh whole blood of the patients. The first-strand cDNA was synthesized and the cDNA of each patient was then tested with 21 pairs of overlapping primers. High resolution melting curve analysis was used to screen FANCA, and LinReg software version 1.7 was utilized for analysis of expression. Results: In total, six sequence alterations were identified, which included two stop codons, two frames-shift mutations, one large deletion and one amino acid exchange. FANCA expression was downregulated in patients who had sequence alterations. Interpretation & conclusions: The results of the present study show that high resolution melting (HRM) curve analysis may be useful in the detection of sequence alteration. It is simpler and more cost-effective than the multiplex ligation-dependent probe amplification (MLPA) procedure.

A novel assay for detecting the mutation of nucleotide 1758-1777 deletion in core promoter region of hepatitis B virus / 解放军医学杂志

Objective Nucleotide (nt) 1758-1777 deletion in core promoter (CP) region of hepatitis B virus (HBV) has been suggested to be associated with disease progression. However, the complicated and less sensitive assay for it limited its use in clinic. The present study was aimed at setting a novel assay for its detection using single-tube nested PCR amplification and real-time PCR melting curve analysis. Methods The PCR primers were designed through analysis of HBV genomic sequences in GenBank, and detection conditions were optimized. HBV CP region from 340 serum samples of chronic hepatitis B patients were amplified and directly sequenced, and fifty samples were randomly selected for cloning and sequencing for analysis of nt 1758-1777 deletion. The wild-type and deletion-type plasmids were extracted from mono-cloning samples. Positive standard of melting curve analysis was set up in light of the results of PCR amplification of two standard plasmids and cloning samples. The new method of assay was used in 340 samples, and the data were verified by the results of pyrosequencing. Results Sixteen (4.7%) samples were positive for the deletion by direct sequencing, and no less than 15% samples in standard plasmids and cloning sequencing showed sequence deletion. The melting temperature (Tm) of deletion-type plasmid and cloning samples containing ≥15% proportion of the deletion sequence was ≥88.3°C, which was determined as positive standard of the novel assay. Forty-seven (13.8%) samples were detected positive for nt 1758-1777 deletion by the novel assay. Among them, deletion ratio was ≥1.0% in 38 samples and <1.0% in 9 samples by pyrosequencing, respectively. The deletion ratio was all <1.0% in 15 negative control samples. The deletion ratio of 1.0% was taken as positive cutoff by pyrosequencing, the novel assay had 80.9% positive consistency and 100% negative consistency, with a Kappa value of 0.671. Conclusions Comparing with direct sequencing, the novel assay significantly increased detection rate of nt 1758-1777 deletion. In combination with pyrosequencing for confirmation, the accuracy and cost-effectiveness of the detection could be significantly improved. The novel assay offers an example for detecting HBV genetic deletions.

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 .

Application of high resolution melting curve analysis technique in detection ofβ-thalassemia gene mutations / 国际检验医学杂志

Objective To investigate the feasibility of high resolution melting(HRM)curve analysis technique for detecting β-thalassemia gene mutations.Methods The HRM method was used to detect five kinds of common β-thalassemia mutations (-28, CD17,CD41-42,CD71-72 and IVS-2-654)in Guangdong province.Sixty specimens of the patients with suspectedβ-thalassemia were performed the HRM analysis.The results of HRM analysis were confirmed by the direct DNA sequencing.Results Among 60 specimens of the patients with suspectedβ-thalassemia,12 cases of heterozygosis mutant gene were detected,including 3 cases of-28,2 cases of CD17,5 cases of CD41-42,2 cases of CD71-72 and 2 cases of IVS-2-654 gene mutation;2 cases of homozygosis mu-tant gene were detected,including 1 case of-28 and 1 case of CD41-42 homozygous mutation (both were amniotic fluid specimens). The results of HRM analysis were consistent with the DNA sequencing results.Conclusion The HRM method can accurately de-tect five kinds of common β-thalassemia mutations in Guangdong province,has the advantages of simpleness,rapidness and high sensitivity and is expected to be a new method for screening β-thalassemia mutation in clinic.

Application of fluorescence PCR melting curve method in drug-resistance detection of Mycobacterium tuberculosis / 国际检验医学杂志

Objective To evaluate the clinical application value of fluorescence PCR melting curve method in the drug-resistance detection of Mycobacterium tuberculosis.Methods With the Lowenstein-Jensen culture method and the absolute concentration method as the comparison,the fluorescent PCR melting curve method was used to detect the resistance to rifampin and isoniazid in 53 cases of pulmonary tuberculosis(TB)respectively.Results The single drug resistance rates and multidrug resistance (MDR) rate detected by the two methods had no significant statistical difference(P >0.05).The comparison between the two methods for detecting the same sample showed that compared with the absolute concentration method,the sensitivity and specificity of the melt-ing curve method for detecting rifampin-resistance,isoniazid-resistance were 80.0% and 81.0%,100.0% and 93.8% respectively, the accuracies were 92.2% and 86.8% respectively,the Kappa values in the consistency analysis of the two methods were 0.754 and 0.710 respectively,indicating the good consistency between them.Conclusion Compared with the traditional methods,the melting curve method has good sensitivity and good specificity with safety,high efficiency and good application value in the treat-ment of drug-resistant pulmonary TB.

Research on Correlation between rs13266634 C/T SNP of SLC30A8 Gene and Susceptibility to Type 2 Diabetes Mellitus / 中国医科大学学报

Objective To investigate the correlation between the rs13266634 C/T SNP of SLC30A8 and T2DM in Jinzhou. Methods Based on case?control study,PCR?HRM was used to identify the genotypes of rs13266634 of SLC30A8 gene in 136 cases of T2DM patients and 145 cases of healthy control in Jinzhou. Results The CC genotypic frequency and C allele frequency in T2DM(38.23%and 61.76%)were higher than those of healthy control(22.07%and 51.03%). Furthermore,there was significant difference in case?control study from the population in Jinzhou(P<0.05). The odds ratio of allele C for T2DM was 1.550(95%CI:1.108?2.169,P<0.05). Conclusion The single nucleotide polymorphism of the rs13266634 locus in SLC30A8gene was correlated with T2DM susceptibility in Jinzhou,and the allele C was a risk allele.

Identification of Brucella melitensis isolates originating from Mongolia and diagnostic real-time PCR evaluation using a specific SNP / 대한수의학회지

A real-time PCR assay using hybridization probe (HybProbe) has been developed to detect Brucella (B.) melitensis strains. The primer and HybProbe sets were designed based on the gap gene of chromosome I with a specific single nucleotide polymorphism of B. melitensis. Specificity of the assay was confirmed by comparison to reference Brucella species and other related strains. In the melting curve analysis, B. melitensis generated a peak at 67degrees C unlike those for other Brucella species observed at 61degrees C. Sensitivity of the assay for B. melitensis ranged from 20 ng to 200 fg of genomic DNA. The ability to identify 94 Mongolian B. melitensis isolates using the real-time PCR assay was identical to that of classical biotyping methods and differential multiplex PCR. These data showed that this new molecular technique is a simple and quick method for detecting B. melitensis, which will be important for the control and prevention of brucellosis.

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.

Clinical evaluation of two gene diagnostic techniques for the detection of drug resistance of Mycobacterium tuberculosis / 实用医学杂志

Objective To evaluate the effect of probe melting curve analysis and gene chips on detecting drug resistance of Mycobacterium tuberculosis against isoniazid and rifampicin. Methods Drug resistance was detected by gene chip and probe melting curve analysis in 46 cases of patients with sputum smear positive specimens, with L-J culture as the gold standard. Results In all the 46 cases, the detection of drug resistance genes against isoniazid was performed by probe melting curve analysis and gene chips, achieving the coincidences of 91.3% and 80.43% with those by L-J culture, respectively. The detection of drug resistance genes in 38 cases administered with rifampicin was conducted as well by the two techniques, achieving the coincidences of 84%and 89.4% with those by L-J culture. There were no significant differences between the two methods (P > 0.05). Conclusion The gene chip direct detection and probe melting curve analysis are of high value in diagnosis of tuberculosis, and they can be regarded as a diagnosis method of choice for tuberculosis. Both have the priorities of timesaving, high sensitivity and specificity.

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 .

Detection and Identification of Six Foodborne Bacteria by Two-tube Multiplex Real Time PCR and Melting Curve Analysis / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>This study is aimed to develop a two-tube melting curve-based multiplex real time PCR assay (MCMRT-PCR) for the simultaneous detection of six common foodborne pathogenic bacteria (diarrhoeagenic Escherichia coli, Salmonella, and Shigella in tube 1, Staphylococcus aureus, Vibrio parahaemolyticus, and Listeria monocytogenes in tube 2).</p><p><b>METHODS</b>A two-tube MCMRT-PCR assay was performed on 7900HT Fast Real-Time PCR System (Applied Biosystems, USA). Amplification by PCR was optimized to obtain high efficiency. The sensitivity and specificity of assays were investigated.</p><p><b>RESULTS</b>The detection limit of optimized MCMRT-PCR assay was 3.9×102 CFU/mL for S. aureus, 4.4×102 CFU/mL for L. monocytogenes, 3.0×102 CFU/mL for Salmonella, 2.5×102 CFU/mL for Shigella, 2.1×102 CFU/mL for V. parahaemolyticus, and 1.2×102 CFU/mL for E. coli. The feasibility of MCMRT-PCR was further evaluated using artificially contaminated milk, the sensitivity was at the level of 105 CFU/mL.</p><p><b>CONCLUSION</b>A two-tube MCMRT-PCR assay using six primer sets was developed for detection of multiple pathogens. Our findings demonstrates that the proposed two-tube assay is reliable, useful and rapid for simultaneous detection of six foodborne pathogenic bacteria with an intended application in provincial Centers for Diseases Control and Prevention (CDC).</p>