Molecular characteristics of rifampin and isoniazid resistant Mycobacterium tuberculosis strains from Beijing, China

Background China is one of the high burden countries of Mycobacterium tuberculosis （TB） infection globally, with high incidence and mortality. We studied the molecular characteristics of rifampin （RIF） and isoniazid （INH） resistant Mycobacterium tuberculosis strains from Beijing, China, in order to find out the genetic marker for rapid detection of specific drug resistance. Methods Forty pansusceptible and 81 resistant strains of Mycobacterium tuberculosis isolated from Beijing, China during 2002-2005 were analyzed. The modified rifampin oligonucleotide （RIFO） assay based on reverse line blot hybridization was used to detect mutations in the 81 bp hot-spot region of rpoB gene, which is associated with RIF resistance. The INH resistance associated genes, regulatory region mab-inhA （-15C/T） and structural gene katG S315T were detected by reverse line blot hybridization and PCR-restriction fragment length polymorphism （RFLP） method respectively. All the strains were typed by spoligotying and the Beijing genotype was further subdivided by NTF locus analysis. The distribution of drug resistance associated mutations in the above genes was compared in these groups. Results Sixty-five （91.5%） of 71 RIF resistant and 52 （92.9%） of 56 multidrug-resistant （MDR, i.e. resistant to at least RIF and INH） strains were found to harbor mutations in the rpoB hot-spot region. No mutation was detected in RIF sensitive strains. The specificity and sensitivity of the modified RIFO assay were 100% and 91.5%, respectively, katG315 AGC〉ACC and inhA-15C〉T mutations were found in 40 （60.6%） and 10 （15.2%） of 66 INH resistant strains, respectively; 7.6% of INH-resistant strains had mutations in both of these genes. Therefore, a combined use of both katG315 and inhA-15 identified 68.2% of INH-resistant strains. The Beijing genotype accounted for 91.7% of total strains and was further subdivided into ＂modern＂ （76.6%） and ＂ancestral＂ （23.4%） group. There is no significant difference between ＂ancestral＂ and ＂modern＂ group in prevalance of drug resistance-associated gene mutations. Conclusions The hot-spot region of rpoB gene can be used as genetic marker for detection of RIF resistant strains; a combined use of both katG315 and inhA-15 can improve the detection rate of I NH resistant strains; the Beijing genotype is prevalent in Beijing, China; the modified RIFO assay can be a practical tool for rapid detection of RIF resistant and MDR isolates in the routine diagnostic work.     

Bioceramics Based on β-Calcium Pyrophosphate

Ceramic samples based on β-calcium pyrophosphate β-Ca₂P₂O₇ were prepared from powders of γ-calcium pyrophosphate γ-Ca₂P₂O₇ with preset molar ratios Ca/P = 1, 0.975 and 0.95 using firing at 900, 1000, and 1100 °C. Calcium lactate pentahydrate Ca(C₃H₅O₃)₂⋅5H₂O and monocalcium phosphate monohydrate Ca(H₂PO₄)₂⋅H₂O were treated in an aqua medium in mechanical activation conditions to prepare powder mixtures with preset molar ratios Ca/P containing calcium hydrophosphates with Ca/P = 1 (precursors of calcium pyrophosphate Ca₂P₂O₇). These powder mixtures containing calcium hydrophosphates with Ca/P = 1 and non-reacted starting salts were heat-treated at 600 °C after drying and disaggregation in acetone. Phase composition of all powder mixtures after heat treatment at 600 °C was presented by γ-calcium pyrophosphate γ-Ca₂P₂O₇ according to the XRD data. The addition of more excess of monocalcium phosphate monohydrate Ca(H₂PO₄)₂·H₂O (with appropriate molar ratio of Ca/P = 1) to the mixture of starting components resulted in lower dimensions of γ-calcium pyrophosphate (γ-Ca₂P₂O₇) individual particles. The grain size of ceramics increased both with the growth in firing temperature and with decreasing molar ratio Ca/P of powder mixtures. Calcium polyphosphate (t _melt = 984 °C), formed from monocalcium phosphate monohydrate Ca(H₂PO₄)₂⋅H₂O, acted similar to a liquid phase sintering additive. It was confirmed by tests in vitro that prepared ceramic materials with preset molar ratios Ca/P = 1, 0.975, and 0.95 and phase composition presented by β-calcium pyrophosphate β-Ca₂P₂O₇ were biocompatible and could maintain bone cells proliferation.     

Evaluation of 5‐Year Risk of Cardiovascular Events in Patients after Acute Myocardial Infarction Using Synchronization of 0.1‐Hz Rhythms in Cardiovascular System

Background: Synchronization between 0.1‐Hz rhythms in cardiovascular system is deteriorated at acute myocardial infarction (AMI) leading to a disruption of natural functional couplings within the system of autonomic regulation. Objective: This study evaluates the prognostic value of autonomic regulation indices for the 5‐year risk of fatal and nonfatal cardiovascular events in patients after AMI. Methods and Results: We studied 125 patients (53 [42%] female) after AMI aged between 30 and 83 years. The period of observation was 5 years with checkpoints at the first week after AMI and after each year after AMI. We compared the prognostic value of established clinical characteristics and degree S of synchronization between 0.1‐Hz rhythms in heart rate and microcirculation for evaluation of the 5‐year risk of mortality and recurrent myocardial infarction (MI) in patients after AMI. Acute heart failure Killip 2–4 at AMI and S < 20% at the first week after AMI were identified as the most important factors for evaluation of the risk of 5‐year mortality in patients after AMI (χ²= 14.2, P = 0.003). Sensitivity and specificity of low S (<20%) at the first week after AMI were 76% and 43%, respectively. For evaluation of the 5‐year risk of recurrent MI index S had no advantage over established clinical characteristics. Conclusion: The value of S below 20% in patients with AMI is a sensitive marker of high risk of mortality during the subsequent five years. It is characterized by better prognostic value than most of established clinical characteristics.