Inferring Mycobacterium Tuberculosis Drug Resistance and Transmission using Whole-genome Sequencing in a High TB-burden Setting in China

Objective China is among the 30 countries with a high burden of tuberculosis(TB)worldwide,and TB remains a public health concern.Kashgar Prefecture in the southern Xinjiang Autonomous Region is considered as one of the highest TB burden regions in China.However,molecular epidemiological studies of Kashgar are lacking.Methods A population-based retrospective study was conducted using whole-genome sequencing(WGS)to determine the characteristics of drug resistance and the transmission patterns.Results A total of 1,668 isolates collected in 2020 were classified into lineages 2(46.0%),3(27.5%),and 4(26.5%).The drug resistance rates revealed by WGS showed that the top three drugs in terms of the resistance rate were isoniazid(7.4%,124/1,668),streptomycin(6.0%,100/1,668),and rifampicin(3.3%,55/1,668).The rate of rifampicin resistance was 1.8%(23/1,290)in the new cases and 9.4%(32/340)in the previously treated cases.Known resistance mutations were detected more frequently in lineage 2 strains than in lineage 3 or 4 strains,respectively:18.6%vs.8.7 or 9%,P<0.001.The estimated proportion of recent transmissions was 25.9%(432/1,668).Multivariate logistic analyses indicated that sex,age,occupation,lineage,and drug resistance were the risk factors for recent transmission.Despite the low rate of drug resistance,drug-resistant strains had a higher risk of recent transmission than the susceptible strains(adjusted odds ratio,1.414;95%CI,1.023–1.954;P=0.036).Among all patients with drug-resistant tuberculosis(DR-TB),78.4%(171/218)were attributed to the transmission of DR-TB strains.Conclusion Our results suggest that drug-resistant strains are more transmissible than susceptible strains and that transmission is the major driving force of the current DR-TB epidemic in Kashgar.

Early Prosthetic Valve Endocarditis with Mycobacterium Tuberculosis after Mitral Valve Replacement: A Case Report

Background: Tuberculous endocarditis is a rare but serious complication of heart valve replacement surgery. We report the case of a 24-year-old patient, who presented with tuberculous endocarditis after mechanical mitral valve replacement, with a favorable clinical course following anti-tuberculosis treatment. Case Presentation: We report a 24-year-old male patient, admitted to the cardiac surgery department of the Fann Hospital (Dakar, Senegal), for the management of severe mixed (rheumatic and endocarditic) mitral insufficiency with associated tricuspid insufficiency. He had a history of recurrent angina and polyarthralgia in childhood, was hospitalized several times for refractory global cardiac decompensation, and for a suspected infective endocarditis a month before his admission. On admission, the clinical examination revealed signs suggestive of mitral and tricuspid insufficiency. Transthoracic echocardiography revealed severe post-endocarditic mitral insufficiency with A3 amputation, highly mobile 15 mm vegetations on the free edge of the large valve, moderate tricuspid insufficiency, and severe pulmonary artery hypertension. Mechanical mitral valve replacement and tricuspid valve annuloplasty using autologous pericardial strip were performed via median sternotomy. After ten days, the patient presented with global cardiac decompensation associated with a clinico-biological infectious syndrome, and tans-oesophageal echography revealed an abscess at the sinotubular junction, communicating with the aorta. A thoraco-abdomino-pelvic CT scan was done, which revealed a bilateral alveolar-interstitial syndrome with mediastinal lymphadenopathy. Anti-tuberculosis treatment with RHZE was initiated for 06 months. The clinical course was favorable. Conclusion: Tuberculous endocarditis in prostheses is a serious complication of heart valve replacement surgery, which may evolve favorably under medical treatment.

Mutation Characteristics of inhA and katG Genes in Isoniazid-Resistant Mycobacterium Tuberculosis Patients in Xinjiang

Objective:To analyze the mutation characteristics of inhA and katG genes in isoniazid-resistant Mycobacterium tuberculosis in Xinjiang.Methods:The katG and inhA in 148 strains of isoniazid-resistant Mycobacterium tuberculosis were amplified through fluorescence quantitative PCR,and the amplified products were sequenced and compared.Results:The inhA gene mutation rate of 148 strains of isoniazid-resistant mycobacterium tuberculosis was 13.51%(20/148),among which the inhA gene mutation rate among patients of Han,Uygur,and Kazakh ethnicity were 15.87%,13.21%,and 17.65%,respectively.There was no significant difference in the inhA mutation rate among nationalities(c^(2)=2.897,P>0.05).The mutation rate of the katG gene was 84.46%(125/148),among which the mutation rates of patients of Han,Uyghur,and Kazak ethnicities were 82.54%,84.91%,and 76.47%,respectively.The Hui and other ethnic groups were all affected by the katG gene mutation.There was no significant difference in the mutation rate of the katG gene among different ethnicities(c^(2)=3.772,P>0.05).The mutation rates of the inhA gene in southern Xinjiang,northern Xinjiang,and other provinces were 18.60%,9.28%,and 37.50%,respectively.The mutation rates of the inhA gene in different regions were statistically different(c^(2)=6.381,P<0.05).There was no significant difference in the inhA mutation rate between patients from southern and northern Xinjiang(c^(2)=2.214,P>0.05)and between southern Xinjiang and other provinces(c^(2)=1.424,P>0.05).However,the mutation rate of the inhA gene in patients from other provinces was higher than that in northern Xinjiang(c^(2)=5.539,P<0.05).The mutation rates of the katG gene in southern Xinjiang,northern Xinjiang,and other provinces were 81.40%,87.63%,and 62.50%,respectively.There was no significant difference in the mutation rates of the katG gene among different regions(c^(2)=3.989,P>0.05).Conclusion:katG gene mutation was predominant in isoniazid-resistant tuberculosis patients in Xinjiang Uygur Autonomous Region,and inhA and katG gene mutation were no different among different ethnic groups.

Characteristics of Mycobacterium tuberculosis serine protease Rv1043c in enzymology and pathogenicity in mice

The serine proteases of Mycobacteria tuberculosis(Mtb)are important contributors to the process of bacterial invasion and its pathogenesis.In the present study,we systematically characterized the role of the Rv1043c protein in Mycobacterium infection by purifying the Rv1043c protein in Escherichia coli and constructing a Mycobacterium smegmatis(Msg)strain overexpressing Rv1043c(Msg_Rv1043c).We found that Rv1043c had serine protease activity and localized to the surface of Mtb.We determined that the optimal pH and temperature for the Rv1043c serine protease were 9.0 and 45°C,respectively.Moreover,the serine protease activity of Rv1043c was enhanced by divalent metal ions of Ca^(2+)and Mg^(2+).Site-directed mutagenesis studies demonstrated that the serine 279 residue in Rv1043c plays a catalytic role.Additionally,mouse model studies confirmed that Rv1043c significantly enhanced the survival of Msg in vivo,induced pulmonary injury and lung cell apoptosis,and promoted the release of pro-inflammatory cytokines interleukin-1βand interleukin-6 in mice.This study presents novel insights into the relationship between mycobacterial serine protease and the pathogenesis of the disease.

Involvement of 2'-5'oligoadenylate synthetase-like proteinin the survivalof Mycobacterium tuberculosis avirulent strain in macrophages

Mycobacterium tuberculosis(M.tuberculosis)can replicate in the macrophage by interfering with many host protein functions.While it is far from known these host proteins for controlling M.tuberculosis infection.Herein,we infected macrophages including THP-1 and Raw264.7 cells with M.tuberculosis and identified the differentially expressed genes(DEGs)in the interferon signaling pathway.Among them,2'-5'oligoadenylate synthetase-like(OASL)underwent the greatest upregulation in M.tuberculosis-infected macrophages.Knockdown of the expression of OASL attenuated M.tuberculosis survival in macrophages.Further,bioinformatics analysis revealed the potential interaction axis of OASL-TAB3-RvO127,which was further validated by the yeast-two-hybrid(Y2H)assay and Co-IP.This interaction axis might regulate the M.tuberculosis survival and proliferation in macrophages.The study reveals a possible role of OASL during M.tuberculosis infection as a target to control its propagation.

Value of ultrasound guided biopsy combined with Xpert Mycobacterium tuberculosis/resistance to rifampin assay in the diagnosis of chest wall tuberculosis

BACKGROUND The thoracic wall lesions,particularly chest wall tuberculosis,and chest wall tumors and other pyogenic wall and actinomycetes infections,almost always present as a diagnostic challenge.AIM To explore the value of ultrasound-guided biopsy combined with the Xpert Mycobacterium tuberculosis/resistance to rifampin(MTB/RIF)assay to diagnose chest wall tuberculosis.METHODS We performed a retrospective study of patients with chest wall lesions from March 2018 to March 2021.All patients received the ultrasound-guided biopsy for pathology examination,acid-fast Bacillus staining,mycobacterial culture,and Xpert MTB/RIF analysis.The sensitivity,specificity,and area under the curve(AUC)were calculated for these diagnostic tests,either individually or combined.Rifampicin resistance results were compared between the mycobacterial culture and the Xpert MTB/RIF assay.RESULTS In 31 patients with the chest wall lesion biopsy,22 patients were diagnosed with chest wall tuberculosis.Of them,3,6,and 21 patients tested positive for mycobacterial culture,acid-fast stain,and Xpert MTB/RIF assay,respectively.The rifampicin resistance results of the 3 culture-positive patients were consistent with their Xpert MTB/RIF assay results.When considering the sensitivity,specificity,and AUC value,the Xpert MTB/RIF assay(95.5%,88.9%,and 0.92,respectively)was a better choice than the acid-fast Bacillus stain(27.3%,100.0%,and 0.64,respectively)and mycobacterial culture(13.6%,100.0%,0.57,respectively).No complications were reported during the procedure.CONCLUSION Ultrasound guided biopsy combined with Xpert MTB/RIF has high value in the diagnosis of chest wall tuberculosis,and can also detect rifampicin resistance.

Research progress on the drug action and resistance mechanism in Mycobacterium tuberculosis

Tuberculosis(TB)is a chronic infectious disease caused by Mycobacterium Tuberculosis(MTB).It is the second largest single cause of death besides novel coronavirus pneumonia.Along with the abuse of antibiotics and extensive use of anti-tuberculosis drugs,multidrug-resistant(MDR)TB,drug-resistant(XDR)TB and totally drug-resistant(TDR)TB became obstacles to the tuberculosis eradication worldwide.According to the World Health Organization(WHO)statistics,China is not only a high burden tuberculosis country in the world,but also a country with a serious epidemic of MDR.Traditional drugs fail to meet the needs of tuberculosis control.Therefore,it is urgent to find new targets of anti-tuberculosis drugs and develop new anti-tuberculosis drugs.Hence,this paper systematically summarizes the mechanism of traditional and newly developed anti-tuberculosis drugs,in which stressing the research progress of drug resistance mechanisms.This work provides us with new insights of new anti-tuberculosis drug developments,and may contribute to a reduction in the harm that tuberculosis brings to society.

Contribution to the Study of Resistance to Anti-Tuberculosis Drugs in the Mycobacterium tuberculosis Complex Isolated at the National Laboratory of Clinical Biology and Public Health in Bangui in the Central African Republic in 2022: Case of Rifampicin

Microscopy-positive and drug-resistant pulmonary tuberculosis (MPT+) is one of the most feared diseases due to the cost of its management and the associated mortality. The GeneXpert, a new molecular test, is in greater demand for the diagnosis of MPT+ resistance cases. The application of GeneXpert to new cases of MPT+ is not effective in the country’s TB screening centres. The objective of this study is to assess the contribution of GeneXpert to the determination of MPT+ resistance cases in Bangui. The study was cross-sectional and covered the period from February to July 2022. The diagnosis of tuberculosis was first performed by microscopy with Ziehl Neelsen hot stain. The GeneXpert was then used to test for resistance in the sputum of all patients with positive microscopy. The collected data was entered into Excel 2013 and analysed with Epi Info 3.3.7. We analysed data from 755 patients, 80 of whom had resistance. The 80 patients ranged in age from 6 to 68 years (mean age = 35 years). The prevalence of resistant TB was 10.60% (80/755). Primary resistance accounted for 73.75% and secondary resistance for 26.25%. The age group 20 - 39 years (57.50%), male (72.50%), 8th district (17.50%), people living in couples (53.75%), farmers (13.75%) were the socio-demographic characteristics most affected by resistance. Treatment failure (13.75%), relapses (13.75%), the notion of contagion (28.75%), a history of smoking (40%) and alcohol (61.25%) were the clinical antecedents reported by the patients. Treatment failure and relapse were the variables associated with the occurrence of resistant PMT+ (p 0.05). A considerable proportion of the overall Mycobacterium tuberculosis resistance to anti-tuberculosis drugs (10.60%) was identified by GeneXpert. Treatment failure and relapse were the factors associated with the risk of resistance.

Molecular Characterization of Drug-Resistant Beijing Family Isolates of Mycobacterium Tuberculosis from Tianjin,China

Objective Tuberculosis remains a severe public health issue, and the Beijing family of mycobacterium tuberculosis （M. tuberculosis） is widespread in East Asia, especially in some areas in China, like Beijing and Tianjin. This study aimed at determining the mutation patterns of drug-resistant Beijing strains of M. tuberculosis isolated from Tianjin, China. Methods A total of 822 M. tuberculosis isolates were screened for drug resistance by an absolute concentration method and the genotype was identified by PCR. 169 drug-resistant isolates of the Beijing family were analyzed for the potential mutations in the rpoB, katG, inhA promoter region and in rpsL, rrs and embB genes, which are associated with resistance to rifampin （RFP）, isoniazid （INH）, streptomycin （SM） and ethambutol （EMB） respectively by PCR and DNA sequencing. Results Fifty-eight out of 63 RFP-resistant isolates were found to carry the mutations within the 81-bp RFP resistance determining region （RRDR） of the rpoB gene and the most frequent mutations occurred at codon 531 （44.4%）, 526 （28.6%）, and 516 （7.9%） respectively. 16 mutation pattems affecting 12 different codons around the RRDR of rpoB were found. Of 116 INH-resistant isolates, 56 （48.3%） had the mutation of katG 315 （AGC→ACC） （Ser→Thr）, 3 （2.6%） carried S315N （AGC→AAC） and 27 （16.0%） had the mutation of inhA-15A→T. 84 out of 122 SM-resistant isolates （68.9%） displayed mutations at the codons 43 or 88 with AAG→AGG （Lys→Arg） of the rpsL gene and 22 （18.0%） with the mutations at positions 513A→C, 516C→T or 905 A→G in the rrs gene. Of 34 EMB-resistant isolates, 6 had mutation with M306V （ATG→GTG）, 3 with M306I （ATG→ATT）, 1 with M306I （ATG→ATA）, 1 with D328Y （GAT→TAT）, 1 with V348L （GTC→CTC）, and 1 with G406S （GGC→AGC） in the embB gene. Conelusion These novel findings extended our understanding of resistance-related mutations in the Beijing strains of M. tuberculosis and may provide a scientific basis for development of new strategies for diagnosis and control of tuberculosis in China and other countries where Beijing strains are prevalent.

Molecular Characterization and Drug-resistance of Mycobacterium tuberculosis Strains in Xuzhou, China

To understand the genetic diversity and drug resistance status of Mycobocterium tuberculosis （M. tuberculosis） circulating in Xuzhou of China, the spacer-oligonucleotide typing （Spoligotyping） and multi-loci VNTRs （variable number tandem repeats） analysis （MLVA） were utilized for the genotyping of the isolates. Drug susceptibility test （DST） was performed by the proportion method on the Lowenstein-Jensen （L-J） medium using isoniazid, rifampicin, ethambutol, and streptomycin. By Spoligotyping, 287 M. tuberculosis isolates were differentiated into 14 clusters. Then with 15-1oci MLVA, these strains could be divided into 32 clusters, 228 genotypes. Of 15 VNTRs, 6 loci had the highly discriminatory powers, 6 loci presented moderate discrimination and 3 loci demonstrated less polymorphism. The DST results showed that 46 strains were resistant to at least one first-line anti-tuberculosis agent. There was a difference in the isoniazid resistance between Beijing and non-Beijing genotype strains. We concluded that the combination of Spoligotyping and 15 VNTR loci as the genotyping in our study was applicable for this region, the drug resistant isolates were identified, and the Beijing family was the most prevalent genotype in the rural counties of Xuzhou.

Specific and cross-reactive immune response against Mycobacterium tuberculosis antigens in mice immunized with proteoliposomes from Mycobacterium bovis BCG

Objective: To characterize the immunogenicity and the induction of cross-reactive responses against Mycobacterium tuberculosis(M. tuberculosis) of a proteoliposome(PL)from Mycobacterium bovis Bacillus Calmette–Guerin(BCG) with and without alum hydroxide(AL) as adjuvant(PLBCG-AL and PLBCG, respectively) in BALB/c mice.Methods: BALB/c mice were inoculated with phosphate buffer solution, BCG, PLBCG and PLBCG-AL. The humoral immunogenicity was determined by ELISA [immunoglobulin G(Ig G), Ig G1 and Ig G2a] and the cellular immunogenicity was evaluated in vivo by delayed type hypersensitivity. The humoral cross-reactive response against M. tuberculosis was determined by Western blot.Results: Sera from animals immunized with PLBCG-AL and PLBCG showed significant increase in specific total Ig G and Ig G1 antibodies and the presence of cross-reactive antibodies against M. tuberculosis antigens, which were more intense with the use of alum as adjuvant. Mice immunized with PLBCG and PLBCG-AL also showed a specific cellular response in vivo.Conclusions: The cellular and humoral immunogenicity of PLBCG and the capacity to induce cross-reactive responses against M. tuberculosis is in agreement with the protective capacity previously demonstrated by this vaccine candidate and supports the continuation of its evaluation in further stages.

Construction, Expression and Identification of a Recombinant BCG Vaccine Encoding Human Mycobacterium Tuberculosis Heat Shock Protein 65

Heat shock protein 65 (HSP65) is one of the most important protective immunogens against the tuberculosis infection. The signal sequence of antigen 85B and the whole HSP65 DNA sequence of human Mycobacterium tuberculosis (M. tuberculosis) were amplified from BCG genome and plasmid pCMV-MTHSP65 respectively by polymerase chain reactions (PCR). These two sequences were cloned into the plasmid pBCG-2100 under the control of the promoter of heat shock protein 70 (HSP70) from human M. tuberculosis, yielding the prokaryotic shuttle expression plasmid pBCG-SP-HSP65. Results of restriction endonuclease analysis, PCR detection and DNA sequencing analysis showed that the two cloned DNA sequences were consistent with those previously reported, and the direction of their inserting into the recombinant was correct and the reading frame had been maintained. The recombinants were electroporated into BCG to construct the recombinant BCG vaccine and induced by heating. The induced expression detected by SDS-PAGE showed that the content of 65 kD protein expressed in recombinant BCG was 35.69 % in total bacterial protein and 74.09 % in the cell lysate supernatants, suggesting that the recombinant HSP65 gene could express in BCG with high efficiency and the expressed proteins were mainly soluble. Western-blot showed that the secretive recombinant proteins could specifically combine with antibody against M. tuberculosis HSP65, indicating that the recombinant proteins possess the biological activity of HSP65.

Identification of distant co-evolving residues in antigen 85C from Mycobacterium tuberculosis using statistical coupling analysis of the esterase family proteins

A fundamental goal in cellular signaling is to understand allosteric communication, the process by which sig-nals originating at one site in a protein propagate reliably to affect distant functional sites. The general principles of protein structure that underlie this process remain unknown. Statistical coupling analysis （SCA） is a statistical technique that uses evolutionary data of a protein family to measure correlation between distant functional sites and suggests allosteric communication. In proteins, very distant and small interactions between collections of amino acids provide the communication which can be important for signaling process. In this paper, we present the SCA of protein alignment of the esterase family （pfam ID： PF00756） containing the sequence of antigen 85C secreted by Mycobacterium tuberculosis to identify a subset of interacting residues. Clustering analysis of the pairwise correlation highlighted seven important residue positions in the esterase family alignments. These resi-dues were then mapped on the crystal structure of antigen 85C （PDB ID： 1DQZ）. The mapping revealed corre-lation between 3 distant residues （Asp38, Leu123 and Met125） and suggests allosteric communication between them. This information can be used for a new drug against this fatal disease.

The Epidemiological Characteristics of Beijing Lineage Mycobacterium tuberculosis from a National Referral Center in China

Our study was to investigate the epidemiological characteristics of M.tuberculosis from a national tuberculosis referral center in China. All strains isolated from TB patients, were genotyped by the RD105 deletion, 8 and 51 SNP loci and VNTR. The high differentiation SNPs of modern Beijing strains were analyzed for protein function and structure. 413 M. tuberculosis were included. Of 379 Beijing lineage M. tuberculosis, ＇modern＇ and ＇ancient＇ strains respectively represented 85.5% （324/379） and 14.5% （55/379）. Rv2494 （V48A） and Rv0245 （Sl03F） were confirmed as high differentiation SNPs associated with modern strains. In a word, Modern Beijing lineage M.tuberculosis was dominant and the structural models suggested that modern sub-lineage may more easily survive in ＇extreme＇ host condition.

Expression,purification and characterization of Mycobacterium tuberculosis RpfE protein

Resuscitation promoting factor E （RpfE） is one of the five Rpf-like proteins in Mycobacterium tuberculos＆ （M. tuberculosis）. These Rpf-like proteins are secretory, which make them candidates for recognition by the host immune system. In this study, the RpfE gene was amplified from M. tuberculosis, cloned into the expression vectors pDE22 and pPRO EXHT, and were expressed in Mycobacterium vaccae （M. vaccae） and Escherichia coli DHSa, respec- tively. Both recombinant RpfE proteins were purified by Ni-Sepharose affinity chromatography, and were given to C57BL/6 mice. The RpfE proteins elicited T cell proliferation, and stimulated the production of gamma interferon （IFN-y）, interleukin-10 （IL-10） and IL-12. Our results indicated that the RpfE protein expressed in M. vaccae could more efficiently stimulate cellular immune response, making it a promising candidate as a subunit vaccine.

Genetic Diversity and Drug Susceptibility of Mycobacterium tuberculosis Isolates in a Remote Mountain Area of China

Objective We determined the genetic diversity of Mycobacterium tuberculosis（MTB） in a remote mountainous area of southwest China and evaluated the resolving ability of single nucleotide polymorphism（SNP） genotyping combined with variable number tandem repeat（VNTR） genotyping for Beijing family strains in association with drug resistance status.Methods Three hundred thirty-one MTB strains were isolated from patients living in mountainous regions of southwest China,and 8-loci SNP,VNTR-15 genotyping assays,and drug susceptibility testing of 9 drugs were performed.Results A total of 183 [55.29%（183/331）] strains were classified into the Beijing family.Of the 183 strains,111（60.66%） were defined as modern Beijing strains.The most predominant modern Beijing sub-lineage and ancient Beijing sub-lineage were Bmyc10 [39.34%（72/183）] and Bmyc25 [20.77%（38/183）],respectively.Of the isolates,19.64%（65/331） were resistant to at least 1 of the 9 anti-TB drugs and 17 [4.98%（17/331）] MTB isolates were multi-drug resistant tuberculosis（MDR-TB）.Two hundred sixty-one isolates showed a clustering rate of 14.18%（37/261） and a discriminatory index of 0.9990.The Beijing lineage exhibited a significantly higher prevalence of MDR-TB,as well as resistance to isoniazid（INH）,rifampin（RIF）,and para-aminosalicylic acid（PAS） when analyzed independently（P = 0.005,P = 0.017,P = 0.014,and P = 0.006 respectively）.The Beijing lineage was not associated with genetic clustering or resistance to any drug.In addition,genetic clustering was not associated with drug resistance.Conclusion MTB strains demonstrate high genetic diversity in remote mountainous areas of southwest China.Beijing strains,especially modern Beijing strains,are predominant in remote mountainous area of China.The combination of 8-loci SNPs and VNTR-15 genotyping is a useful tool to study the molecular epidemiology of MTB strains in this area.

Biological functions and diagnostic implications of microRNAs in Mycobacterium tuberculosis infection

MicroRNAs(miRNAs),small non-coding RNAs,play important roles in regulating host defense against pathogenic infections.This review provides information on the role of miRNAs in the antimycobacterial immune response and summarizes their possible diagnostic utility.It was compiled using scientific literature retrieved from such databases as PubMed,Scopus,ScienceDirect,Google Scholar,and PubMed Central.Relevant articles published in the English language until December 2020 were taken into consideration.It has been revealed that specific host miRNAs induced by Mycobacterium tuberculosis can target diverse factors and pathways in immune signaling to ensure longer pathogen survival inside the phagocytes.The potential use of miRNAs in tuberculosis diagnosis or therapeutic strategies has been attracting increasing attention in recent years.However,despite considerable efforts devoted to miRNA profiling,further studies are needed to elucidate the full potential of miRNAs as novel tuberculosis biomarkers or therapeutic targets.

Screening Peptide Inhibitors Using Phage Peptide Library with Isocitrate Lyase in Mycobacterium tuberculosis as Target

When devoured by macrophages,Mycobacterium tuberculosis remains persistent in macrophages and gains energy through the glyoxylate bypass to maintain its long-term existence in host cells.Therefore it is possible to stop persistent infections by interdicting the glyoxylate bypass in which the isocitrate lyase（ICL） is the key rate-limiting enzyme and a persistence factor.ICL is the target of anti-TB（TB：tubercular） drugs,which could screen ICL out and effectively inhibit the activity of ICL in Mycobacterium tuberculosis,and because of this,anti-TB drugs can be used to kill persistent Mycobacterium tuberculosis.In this study,the ICL gene of the Mycobacterium tuberculosis H37Rv was cloned successfully and recombinant protein with bioactivity was obtained through the enzyme characteristic appraisal.The specific activity of the recombined ICL is 24μmol·mg-1·min-1.The recombined ICL protein was used as the target,and phages which can specifically combine to ICL were screened in the phage 7 peptide library.According to the results of the ELISA and DNA sequence detection,eventually three 7-peptide chains were synthesized.Then the peptide chains were reacted with ICL,respectively,to detect their inhibitory effects on ICL.The results show that all the three 7-peptide chains possessed varying inhibitory effects on the activity of ICL.This study provided lead compounds for the research and development of new peptide anti-TB drugs.

Evaluation of Four Candidate VNTR Loci for Genotyping 225 Chinese Clinical Mycobacterium Tuberculosis Complex Strains

Objective To evaluate four candidate variable number tandem repeat （VNTR） loci for genotyping Mycobacterium tuberculosis complex strains. Methods Genomic sequences for two M. tuberculosis strains （CCDC5079 and CCDC5180） were generated, and using published sequence data, four candidate VNTR loci were identified. The VNTRs were used to genotype 225 Chinese clinical M. tuberculosis complex strains. The discriminatory power of the VNTRs was evaluated using BioNumerics 5.0 software. Results The Hunter-Gaston Index （HGI） for BJ1, BJ2, BJ3, and BJ4 loci was 0.634, 0.917, 0.697, and 0.910, respectively. Combining all four loci gave an HGI value of 0.995, thus confirming that the genotyping had good discriminatory power. The HGI values for BJ1, BJ2, BJ3, and BJ4, obtained from Beijing family strain genotyping, were 0.447, 0.878, 0.315, and 0.850, respectively. Combining all four loci produced an HGI value of 0.988 for genotyping the Beijing family strains. We observed unique patterns for M. boris and M. africanum strains from the four loci. Conclusion We have shown that the four VNTR loci can be successfully used for genotyping M. tuberculosis complex strains. Notably, these new loci may provide additional information about Chinese M. tuberculosis isolates than that currently afforded by established VNTR loci typing.

Rapid Detection of Rifampin-resistant Clinical Isolates of Mycobacterium tuberculosis by Reverse Dot Blot Hybridization

Objective A PCR-reverse dot blot hybridization （RDBH） assay was developed for rapid detection of rpoB gene mutations in ＇hot mutation region＇ of Mycobacterium tuberculosis （M. tuberculosis）. Methods 12 oligonucleotide probes based on the wild-type and mutant genotype rpoB sequences of M. tuberculosis were designed to screen the most frequent wild-type and mutant genotypes for diagnosing RIF resistance. 300 M. tuberculosis clinical isolates were detected by RDBH, conventional drug-susceptibility testing （DST） and DNA sequencing to evaluate the RDBH assay. Results The sensitivity and specificity of the RDBH assay were 91.2% （165/181） and 98.3% （117/119）, respectively, as compared to DST. When compared with DNA sequencing, the accuracy, positive predictive value （PPV） and negative predictive value （NPV） of the RDBH assay were 97.7% （293/300）, 98.2% （164/167）, and 97.0% （129/133）, respectively. Furthermore, the results indicated that the most common mutations were in codons 531 （48.6%）, 526 （25.4%）, 516 （8.8%）, and 511 （6.6%）, and the combinative mutation rate was 15 （8.3%）. One and two strains of insertion and deletion were found among all strains, respectively. Conclusion Our findings demonstrate that the RDBH assay is a rapid, simple and sensitive method for diagnosing RIF-resistant tuberculosis.