PLGA Carriers for Controlled Release of Levofloxacin in Anti-Tuberculosis Therapy

Levofloxacin (LFX) is a highly effective anti-tuberculosis drug with a pronounced bactericidal activity against Mycobacterium tuberculosis (Mtb). In this work, an “organic solvent-free” approach has been used for the development of polylactic-co-glycolic acid (PLGA) microparticles and scaffolds containing LFX at a therapeutically significant concentration, providing for its sustained release. To achieve the target, both nonpolar supercritical carbon dioxide and polar supercritical trifluoromethane have been used. By changing the composition, surface morphology, size, and internal structure of the polymer carriers, one can control the kinetics of the LFX release into phosphate buffered saline solutions and physiological media, providing for its acceptable burst and desirable concentration in the prolonged phase. The biocompatibility and bactericidal efficacy of PLGA/LFX carriers assessed both in vitro (against Mtb phagocytosed by macrophages) and in vivo (against inbred BALB/c mice aerogenically infected with Mtb) demonstrated their anti-tuberculosis activity comparable with that of the standard daily intragastric levofloxacin administration. These results make it possible to consider the developed compositions as a promising candidate for anti-tuberculosis control release formulations providing for the further evaluation of their activity against Mtb and their metabolism in vivo over long periods of tuberculosis infection.

New in vitro model to evaluate kinetics of antimycobacterial drug release from bioresorbable polymeric carriers

Sustained-release drugs against tuberculosis are a promising approach to therapy since they positively affect patient compliance with long regimens, especially when it comes to the multidrug-resistant form of the disease. Conventional UV-visible spectroscopy does not work well with multicomponential culture media used for growing M. tuberculosis. The aim of this study was to develop a method for evaluating the kinetics of anti-tuberculosis drug released from bioresorbable polymeric carriers suitable for screening a wide range of encapsulated prolonged-release drugs and identifying the best performing candidate. While studying the growth dynamics of the laboratory susceptible strain M. tuberculosis H37Rv in the presence of different levofloxacin concentrations (from 0.03 to 0.4 μg/ml), we developed a model, which is essentially a set of 2 parallel experiments evaluating the kinetics of drug release into the culture medium. The results of these 2 experiments conducted on 3 encapsulated forms of levofloxacin loaded onto bioresorbable polymeric PLGA carriers (particles sized 50 μm and 100 μm and the matrix) revealed that release kinetics of the drug largely depended on the type of polymeric carrier. The best encapsulation of the antibiotic and its gradual release into the culture medium was observed for the matrix. All experiments were run in 3 replicates. The obtained data were analyzed using descriptive statistics.

New assay to diagnose and differentiate between Mycobacterium tuberculosis complex and nontuberculous mycobacteria

The purpose of the present study was to create a real-time PCR test system allowing simultaneous detection of nontuberculous mycobacteria (NTM) and Mycobacterium tuberculosis complex (MTBC) both in culture and sputum. NTM cultures (18 strains, 18 species), MTBC cultures (16 strains, 2 species) and non-mycobacterial microorganisms from the collection of the Central Research TB Institute (CTRI) were used for the preliminary evaluation of the test system. 301 NTM cultures from patients with mycobacteriosis were used to assess the sensitivity of the developed test system. Clinical respiratory samples (sputum) from 104 patients with mycobacteriosis, 3627 patients with tuberculosis and 118 patients with other lung diseases were used for diagnostic sensitivity and specificity testing. The specificity and sensitivity of the assay for MTBC was found to be 100% both in culture and sputum samples; for NTM, the specificity was 100% in culture and sputum, the sensitivity reached 100% in culture and 73.1% in sputum samples. Positive predictive value (PPV) and negative predictive value (NPV) of the assay for culture were both 100%, for clinical material 100% and 80.8%, respectively. The limit of detection at the probability of detection 95% (LoD95%) was estimated to be 16 cfu/ml for M. tuberculosis H37RV and 1200 cfu/ml for M. avium.

Non-invasive approach to diagnosis of pulmonary tuberculosis using microdroplets collected from exhaled air

In this report we present a proof-of-principle study aimed at developing non-invasive diagnostics for pulmonary TB that are based on analyzing TB biomarkers in exhaled microdroplets of lung fluid (MLFs). Samples were collected on electrospun filters recently developed by the authors, and then tested for the presence of Mycobacterium tuberculosis (Mtb) cells, Mtb DNA, and protein biomarkers (secreted Mtb antigens and antigen-specific antibodies). The latter were detected using rapid ultra-sensitive immunochemistry methods developed in our laboratory. Neither Mtb cells (limit of detection, LOD = 1 cell) nor Mtb DNA (LOD ∼ 10 CFU) were found in the MLF samples exhaled by TB patients. However, immunoglobulin A (IgA) was found in over 90% of samples from TB patients and healthy volunteers. Antigen-specific IgA were detected at higher rates in the patient samples as compared to those from nominally healthy volunteers resulting in a modest discrimination level of 72% sensitivity and 58% specificity. As such, this novel, non-invasive and fast breath diagnostic method shows promise for further development.

Severe Tuberculosis in Humans Correlates Best with Neutrophil Abundance and Lymphocyte Deficiency and Does Not Correlate with Antigen-Specific CD4 T-Cell Response

It is generally thought that Mycobacterium tuberculosis (Mtb)-specific CD4⁺ Th1 cells producing IFN-γ are essential for protection against tuberculosis (TB). In some studies, protection has recently been associated with polyfunctional subpopulation of Mtb-specific Th1 cells, i.e., with cells able to simultaneously secrete several type 1 cytokines. However, the role for Mtb-specific Th1 cells and their polyfunctional subpopulations during established TB disease is not fully defined. Pulmonary TB is characterized by a great variability of disease manifestations. To address the role for Mtb-specific Th1 responses during TB, we investigated how Th1 and other immune cells correlated with particular TB manifestations, such as the degree of pulmonary destruction, TB extent, the level of bacteria excretion, clinical disease severity, clinical TB forms, and “Timika X-ray score,” an integrative parameter of pulmonary TB pathology. In comparison with healthy Mtb-exposed controls, TB patients (TBP) did not exhibit deficiency in Mtb-specific cytokine-producing CD4⁺ cells circulating in the blood and differed by a polyfunctional profile of these cells, which was biased toward the accumulation of bifunctional TNF-α⁺IFN-γ⁺IL-2⁻ lymphocytes. Importantly, however, severity of different TB manifestations was not associated with Mtb-specific cytokine-producing cells or their polyfunctional profile. In contrast, several TB manifestations were strongly correlated with leukocyte numbers, the percent or the absolute number of lymphocytes, segmented or band neutrophils. In multiple alternative statistical analyses, band neutrophils appeared as the strongest positive correlate of pulmonary destruction, bacteria excretion, and “Timika X-ray score.” In contrast, clinical TB severity was primarily and inversely correlated with the number of lymphocytes in the blood. The results suggest that: (i) different TB manifestations may be driven by distinct mechanisms; (ii) quantitative parameters and polyfunctional profile of circulating Mtb-specific CD4⁺ cells play a minor role in determining TB severity; and (iii) general shifts in production/removal of granulocytic and lymphocytic lineages represent an important factor of TB pathogenesis. Mechanisms leading to these shifts and their specific role during TB are yet to be determined but are likely to involve changes in human hematopoietic system.

[The Spectrum of Mutations in Genes Associated with Resistance to Rifampicin, Isoniazid, and Fluoroquinolones in the Clinical Strains of M. tuberculosis Reflects the Transmissibility of Mutant Clones]

To study the transmissibility of drug resistant mutant clones, M. tuberculosis samples were isolated from the patients of the clinical department and the polyclinic of the Central TB Research Institute (n = 1455) for 2011-2014. A number of clones were phenotypically resistant to rifampicin (n = 829), isoniazid (n = 968), and fluoroquinolones (n = 220). We have detected 21 resistance-associated variants in eight codons of rpoB, six variants in three codons of katG, three variants in two positions of inhA, four variants in four positions of ahpC, and nine variants in five codons of gyrA, which were represented in the analyzed samples with varied frequencies. Most common mutations were rpoB 531 Ser→Leu (77.93%), katG 315 (Ser→Thr) (94.11%), and gyrA 94 (Asp→Gly) (45.45%). We found that the mutations at position 15 of inhA (C→T) (frequency of 25.72%) are commonly associated with katG 315 (Ser→Thr). This association of two DNA variants may arise due to the double selection by coexposure of M. tuberculosis to isoniazid and ethionamide. The high transmissibility of mutated strains was observed, which may be explained by the minimal influence of the resistance determinants on strain viability. The high transmissibility of resistant variants may also explain the large populational prevalence of drug-resistant TB strains.

Mycobacterium tuberculosis Type II Toxin-Antitoxin Systems: Genetic Polymorphisms and Functional Properties and the Possibility of Their Use for Genotyping

Various genetic markers such as IS-elements, DR-elements, variable number tandem repeats (VNTR), single nucleotide polymorphisms (SNPs) in housekeeping genes and other groups of genes are being used for genotyping. We propose a different approach. We suggest the type II toxin-antitoxin (TA) systems, which play a significant role in the formation of pathogenicity, tolerance and persistence phenotypes, and thus in the survival of Mycobacterium tuberculosis in the host organism at various developmental stages (colonization, infection of macrophages, etc.), as the marker genes. Most genes of TA systems function together, forming a single network: an antitoxin from one pair may interact with toxins from other pairs and even from other families. In this work a bioinformatics analysis of genes of the type II TA systems from 173 sequenced genomes of M. tuberculosis was performed. A number of genes of type II TA systems were found to carry SNPs that correlate with specific genotypes. We propose a minimally sufficient set of genes of TA systems for separation of M. tuberculosis strains at nine basic genotype and for further division into subtypes. Using this set of genes, we genotyped a collection consisting of 62 clinical isolates of M. tuberculosis. The possibility of using our set of genes for genotyping using PCR is also demonstrated.

Multidrug-Resistant Tuberculosis Treatment Outcomes in Relation to Treatment and Initial Versus Acquired Second-Line Drug Resistance

BACKGROUND

Resistance to second-line drugs develops during treatment of multidrug-resistant (MDR) tuberculosis, but the impact on treatment outcome has not been determined.

METHODS

Patients with MDR tuberculosis starting second-line drug treatment were enrolled in a prospective cohort study. Sputum cultures were analyzed at a central reference laboratory. We compared subjects with successful and poor treatment outcomes in terms of (1) initial and acquired resistance to fluoroquinolones and second-line injectable drugs (SLIs) and (2) treatment regimens.

RESULTS

Of 1244 patients with MDR tuberculosis, 973 (78.2%) had known outcomes and 232 (18.6%) were lost to follow-up. Among those with known outcomes, treatment succeeded in 85.8% with plain MDR tuberculosis, 69.7% with initial resistance to either a fluoroquinolone or an SLI, 37.5% with acquired resistance to a fluoroquinolone or SLI, 29.3% with initial and 13.0% with acquired extensively drug-resistant tuberculosis (P < .001 for trend). In contrast, among those with known outcomes, treatment success increased stepwise from 41.6% to 92.3% as the number of drugs proven effective increased from ≤1 to ≥5 (P < .001 for trend), while acquired drug resistance decreased from 12% to 16% range, depending on the drug, down to 0%-2% (P < .001 for trend). In multivariable analysis, the adjusted odds of treatment success decreased 0.62-fold (95% confidence interval, .56-.69) for each increment in drug resistance and increased 2.1-fold (1.40-3.18) for each additional effective drug, controlling for differences between programs and patients. Specific treatment, patient, and program variables were also associated with treatment outcome.

CONCLUSIONS

Increasing drug resistance was associated in a logical stepwise manner with poor treatment outcomes. Acquired resistance was worse than initial resistance to the same drugs. Increasing numbers of effective drugs, specific drugs, and specific program characteristics were associated with better outcomes and less acquired resistance.

Resistance to pyrazinamide in Russian Mycobacterium tuberculosis isolates: pncA sequencing versus Bactec MGIT 960

Resistance to pyrazinamide (PZA) may impact clinical outcome of anti-tuberculosis chemotherapy. PZA susceptibility testing using MGIT 960 is not reliable and little information is available on the prevalence of PZA resistance in Russia. A collection of 64 clinical isolates of Mycobacterium tuberculosis, including 35 multidrug resistant and extensively drug-resistant (MDR/XDR), was analyzed for PZA resistance using MGIT 960, Wayne test, and sequencing of PZA resistance genes pncA, rpsA and panD. In addition, we analyzed 519 MDR-TB strains for susceptibility to PZA by MGIT 960. Sequencing of pncA revealed 17 of 25 (68%) MDR strains and all 10 XDR strains harboring pncA mutations. A correlation of φ = 0.81 between MGIT 960 and pncA sequencing was observed. Mutations in rpsA and panD not associated with PZA resistance as defined by MGIT 960 were identified. We found 1 PZA-resistant strain without mutations in known PZA resistance genes. Almost 73% of MDR-TB strains isolated in Moscow, Russia, were PZA-resistant by MGIT 960 testing of 519 MDR-TB clinical isolates. Further studies are needed to determine the role of rpsA and panD mutations in possible low-level PZA resistance and to identify the molecular basis of new PZA resistance in the isolate without known PZA resistance mutations.

[[Length polymorphism of minisatellite repeat B2-VNTR of the bradykinin B2 receptor gene in healthy Russians and in patients with coronary heart disease]

Bradykinin B2 receptor is involved in many processes, including the regulation of blood pressure and smooth muscle contraction, vasodilation, inflammation, edema, cell proliferation, pain. It is suggested that this receptor may be one of the factors that have cardioprotective and infarct-limiting effects. It is assumed that certain genetic variants in both coding and non-coding regions ofBDKRB2 gene may influence its expression. In the 3'-untranslated region of BDKRB2 exon 3 the minisatellite repeat B2-VNTR is located. B2-VNTR has previously been shown to affect the BDKRB2 mRNA stability. Therefore, it is important to perform the molecular genetic analysis of this minisatellite in patients with different forms of coronary heart disease in order to reveal possible associations between specific B2-VNTR alleles and certain clinical forms of coronary heart disease. In the present study, a comparative analysis of the allele and genotype frequencies of B2-VNTR was carried out in groups of healthy individuals and patients with two clinical forms of coronary heart disease (angina pectoris and myocardial infarction), ethnically Russian. The results of the B2-VNTR length polymorphism analysis indicate that this tandem repeat may be attributed to a class of low polymorphic and non-hypervariable minisatellite. In all analyzed groups we revealed three B2-VNTR alleles, consisting of 43, 38 and 33 repeat units. Alleles of 43 and 33 repeats were major in all investigated groups. No statistically significant differences were found in the B2-VNTR allele and genotype frequencies between men and women in control group, and also between healthy men and men with angina pectoris and myocardial infarction. Thus, B2-VNTR length polymorphism was not associated with these clinical forms of coronary heart disease in Russian men. However, we do not exclude the possibility of association between the B2-VNTR short alleles (38 and 33 repeats) and cardioprotective effects of bradykinin B2 receptor in women with coronary heart disease. This hypothesis requires further investigation.

Comparative genomic analysis of Mycobacterium tuberculosis drug resistant strains from Russia

Tuberculosis caused by multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis (MTB) strains is a growing problem in many countries. The availability of the complete nucleotide sequences of several MTB genomes allows to use the comparative genomics as a tool to study the relationships of strains and differences in their evolutionary history including acquisition of drug-resistance. In our work, we sequenced three genomes of Russian MTB strains of different phenotypes--drug susceptible, MDR and XDR. Of them, MDR and XDR strains were collected in Tomsk (Siberia, Russia) during the local TB outbreak in 1998-1999 and belonged to rare KQ and KY families in accordance with IS6110 typing, which are considered endemic for Russia. Based on phylogenetic analysis, our isolates belonged to different genetic families, Beijing, Ural and LAM, which made the direct comparison of their genomes impossible. For this reason we performed their comparison in the broader context of all M. tuberculosis genomes available in GenBank. The list of unique individual non-synonymous SNPs for each sequenced isolate was formed by comparison with all SNPs detected within the same phylogenetic group. For further functional analysis, all proteins with unique SNPs were ascribed to 20 different functional classes based on Clusters of Orthologous Groups (COG). We have confirmed drug resistant status of our isolates that harbored almost all known drug-resistance associated mutations. Unique SNPs of an XDR isolate CTRI-4(XDR), belonging to a Beijing family were compared in more detail with SNPs of additional 14 Russian XDR strains of the same family. Only type specific mutations in genes of repair, replication and recombination system (COG category L) were found common within this group. Probably the other unique SNPs discovered in CTRI-4(XDR) may have an important role in adaptation of this microorganism to its surrounding and in escape from antituberculosis drugs treatment.

Performance of Cepheid ® Xpert MTB/RIF ® and TB-Biochip ® MDR in two regions of Russia with a high prevalence of drug-resistant tuberculosis

The purpose of this study was to assess the performance of Cepheid® Xpert MTB/RIF® ("Xpert") and TB-Biochip® MDR ("TB-Biochip"). Sputum specimens from adults with presumptive tuberculosis (TB) were homogenized and split for: (1) direct Xpert and microscopy, and (2) concentration for Xpert, microscopy, culture [Lowenstein-Jensen (LJ) solid media and Mycobacteria Growth Indicator Tube® (MGIT)], indirect drug susceptibility testing (DST) using the absolute concentration method and MGIT, and TB-Biochip. In total, 109 of 238 (45.8 %) specimens were culture-positive for Mycobacterium tuberculosis complex (MTBC), and, of these, 67 isolates were rifampicin resistant (RIF-R) by phenotypic DST and 64/67 (95.5 %) were isoniazid resistant (INH-R). Compared to culture of the same specimen, a single direct Xpert was more sensitive for detecting MTBC [95.3 %, 95 % confidence interval (CI), 90.0-98.3 %] than direct (59.6 %, 95 % CI, 50.2-68.5 %) or concentrated smear (85.3 %, 95 % CI, 77.7-91.1 %) or LJ culture (80.8 %, 95 % CI, 72.4-87.5 %); the specificity was 86.0 % (95 % CI, 78.9-91.3 %). Compared with MGIT DST, Xpert correctly identified 98.2 % (95 % CI, 91.5-99.9 %) of RIF-R and 95.5 % (95 % CI, 85.8-99.2 %) of RIF-susceptible (RIF-S) specimens. In a subset of 104 specimens, the sensitivity of TB-Biochip for MTBC detection compared to culture was 97.3 % (95 % CI, 91.0-99.5 %); the specificity was 78.1 % (95 % CI, 61.5-89.9 %). TB-Biochip correctly identified 100 % (95 % CI, 94.2-100 %) of RIF-R, 94.7 % (95 % CI, 76.7-99.7 %) of RIF-S, 98.2 % (95 % CI, 91.4-99.9 %) of INH-R, and 78.6 % (95 % CI, 52.1-94.2 %) of INH-S specimens compared to MGIT DST. Xpert and Biochip were similar in accuracy for detecting MTBC and RIF resistance compared to conventional culture methods.

Prevalence of and risk factors for resistance to second-line drugs in people with multidrug-resistant tuberculosis in eight countries: a prospective cohort study

BACKGROUND

The prevalence of extensively drug-resistant (XDR) tuberculosis is increasing due to the expanded use of second-line drugs in people with multidrug-resistant (MDR) disease. We prospectively assessed resistance to second-line antituberculosis drugs in eight countries.

METHODS

From Jan 1, 2005, to Dec 31, 2008, we enrolled consecutive adults with locally confirmed pulmonary MDR tuberculosis at the start of second-line treatment in Estonia, Latvia, Peru, Philippines, Russia, South Africa, South Korea, and Thailand. Drug-susceptibility testing for study purposes was done centrally at the Centers for Disease Control and Prevention for 11 first-line and second-line drugs. We compared the results with clinical and epidemiological data to identify risk factors for resistance to second-line drugs and XDR tuberculosis.

FINDINGS

Among 1278 patients, 43·7% showed resistance to at least one second-line drug, 20·0% to at least one second-line injectable drug, and 12·9% to at least one fluoroquinolone. 6·7% of patients had XDR tuberculosis (range across study sites 0·8-15·2%). Previous treatment with second-line drugs was consistently the strongest risk factor for resistance to these drugs, which increased the risk of XDR tuberculosis by more than four times. Fluoroquinolone resistance and XDR tuberculosis were more frequent in women than in men. Unemployment, alcohol abuse, and smoking were associated with resistance to second-line injectable drugs across countries. Other risk factors differed between drugs and countries.

INTERPRETATION

Previous treatment with second-line drugs is a strong, consistent risk factor for resistance to these drugs, including XDR tuberculosis. Representative drug-susceptibility results could guide in-country policies for laboratory capacity and diagnostic strategies.

FUNDING

US Agency for International Development, Centers for Disease Control and Prevention, National Institutes of Health/National Institute of Allergy and Infectious Diseases, and Korean Ministry of Health and Welfare.

[Regulatory effect of complex of natural cytokines and antimicrobial peptides on murine macrophages infected with multidrug-resistant Mycobacterium tuberculosis]

AIM

To study the effect of complex of natural cytokines and antimicrobial peptides (CNCAP) included in preparation Superlymph on growth of multidrug-resistant Mycobacterium tuberculosis CN-37 on the modem of murine peritoneal macrophages (MPh) cultivated in vitro.

MATERIALS AND METHODS

Effect of CNCAP on peritoneal MPh of tuberculosis-susceptible mice C57BL/6 infected by M. tuberculosis CN-37 was studied using ex vivo model. Macrophages were preliminary incubated with CNCAP during one day. M. tuberculosis growth was assessed on 7th day by PCR.

RESULTS

Preliminary incubation of infected MPh with CNCAP resulted in inhibition of M. tuberculosis CN-37 growth.

CONCLUSION

Superlymph activates macrophages which lead to enhanced bactericidal action of MPh on M. tuberculosis CN-37.

[Detection of mutations in codon 306 of the embB gene for molecular genetic characterization of clinical Mycobacterium tuberculosis strains]

A total of 254 Mycobacterium tuberculosis strains were used in the study. Among them, there were 183 ethambutol (EMB)-resistant strains, 13 multidrug resistant ones, but EMB-sensitive, and 39 strains sensitive to rifampicin (RIF), isoniazid (INZ), and EMB. All the strains were analyzed for genetic changes in three loci: embB306, rpoB, and katG/inhA promoter, which were associated with the formation of resistance to EMB, RIF, and INZ, respectively. The Mycobacterium tuberculosis strains were obtained from pulmonary tuberculosis patients living in the Central Region of the Russian Federation. Resistance to RIF, INZ, and EMB was revealed by the absolute concentration test. The inhibitory concentration (IC) of EMB was determined for all the strains. Genetic changes in the above loci were estimated by mini-sequencing, followed by mass-spectrometry recording MALDI-TOF products. The relative low frequency of embB306 mutations was observed among the EMB-resistant strains (about 41.5%). Mutations in codon 306 were detected only in strains with EMB IC > or = 2 mg/L. A statistical significant association was found between the frequency of embB306 mutations and the multidrug resistant phenotype. A combination of these mutations with the traditional genetic markers of multidrug resistance may be used for the more effective detection of multidrug-resistant strains.

[Inhibiting effect of complex of natural cytokines and cationic antimicrobial peptides on the growth of Mycobacterium tuberculosis H37Rv in vitro]

AIM

To assess direct antimicrobial effect of complex of natural cytokines (CNC) and antimicrobial peptides (Syperlymph preparation; CNC) on Mycobacterium tuberculosis H37Rv (H37Rv) and effect mediated by macrophages (MP) treated with the preparation.

MATERIALS AND METHODS

Direct effect of CNC was studied during cultivation of H37Rv in the presence of preparation, whereas indirect effects--during simultaneous cultivation of H37Rv and mice peritoneal MP C57B1/6. Assessment of growth was performed on the 7th day using PCR.

RESULTS

It was shown that CNC directly inhibits growth of H37Rv in vitro. Cultivation of H37Rv in culture of MP resulted in inhibition of M. tuberculosis. The most evident inhibition was noted after extension of time of preliminary treatment of MP with Syperlymph and simultaneous increase of its concentration.

CONCLUSION

Antimycobacterial effect of Syperlymph preparation related to complex effect of cytokines and antimicrobial peptides directed to M. tuberculosis and macrophages, which forms the conditions for killing of mycobacteria.

[Biological properties of M. Tuberculosis W cluster strains]

To study the biological characteristics of M. tuberculosis W cluster strains, the authors carried out in vitro, ex vivo, and in vivo experiments on 18 clinical strains and 2 laboratory ones, which had been clustered by a standardized methodology. Comparison was made in experiments in vitro and in macrophageal inoculation (ex vivo) from the 5,6-[3H]-uracil incorporation that reflected mycobacterial replication. The in vivo experiments estimated mycobacterial survival and cultivation and the lung pathomorphological pattern of infected animals. The results showed that M. tuberculosis W cluster strains had in vitro the mean multiplication rate, showing a high viability in the macrophages; the in vivo experiments demonstrated that the W cluster strains did not differ in virulence and might be both more and less virulent than the laboratory strain H37Rv. Notwithstanding the fact that the assumption on the hypervirulence of M. tuberculosis W cluster has not been supported, the distinguishing characteristic of the strains of this cluster is their enhanced capacity to survive in the macrophages no matter what infective dose.

Mass-spectrometry based minisequencing method for the rapid detection of drug resistance in Mycobacterium tuberculosis

A MALDI TOF MS based minisequencing method has been developed and applied for the analysis of rifampin (RIF)- and isoniazid (INH)-resistant M. tuberculosis strains. Eight genetic markers of RIF resistance-nucleotide polymorphisms located in RRDR of rpoB gene, and three of INH resistance including codon 315 of katG gene and -8 and -15 positions of the promoter region of fabG1-inhA operon were worked out. Based on the analysis of 100 M. tuberculosis strains collected from the Moscow region in 1997-2005 we deduced that 91% of RIF-resistant and 94% of INH-resistant strains can be identified using the technique suggested. The approach is rapid, reliable and allows to reveal the drug resistance of M. tuberculosis strains within 12 h after sample isolation.

Molecular characteristics of rifampicin- and isoniazid-resistant Mycobacterium tuberculosis isolates from the Russian Federation

OBJECTIVES

Three Mycobacterium tuberculosis genetic loci--rpoB and katG genes and the fabG1(mabA)-inhA operon promoter region--were studied to reveal the mutations associated with rifampicin and isoniazid resistance.

METHODS

Four hundred and twelve isolates of M. tuberculosis from different regions of the Russian Federation were collected during 1997-2005. A matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS)-based minisequencing method was used for the detection of mutations.

RESULTS

Thirteen different variants of single mutations in codons 533, 531, 526, 516, 513 and 511 of the rifampicin resistance-determining region of the rpoB gene as well as the TTG insertion in the 514a position were found among the rifampicin-resistant isolates. Single nucleotide substitutions in codons 531, 526 and 516 (64.8%, 10.3% and 7.7%, respectively) were the most prevalent mutations. Codon 526 was shown to be the most variable of all. No mutations were detected in rpoB genes for 29 (10.7%) of the rifampicin-resistant isolates. 76.9% of the isoniazid-resistant isolates carried single mutations in codon 315 of the katG gene. For another 12.9% of them, double mutations in the katG gene and the fabG1(mabA)-inhA promoter region were revealed. No mutations were detected in 8.2% of the isoniazid-resistant isolates.

CONCLUSIONS

Molecular analysis of the loci of rpoB and katG genes and the inhA promoter region of 412 M. tuberculosis clinical isolates from various parts of the Russian Federation was carried out. The new MALDI-TOF MS-based method may be used for rapid and accurate monitoring of the spread of drug resistance.

[Impact of M. tuberculosis genotype on survival in mice with experimental tuberculosis]

To study the virulence of Mycobacterium tuberculosis strains of the W cluster, C57B1/6 mice were intravenously inoculated with a lethal dose (5x10(6) CFU) of 14 clinical M. tuberculosis strains (11 drug-sensitive and 3 multidrug-resistant) belonging to different RFDP IS6110 genotypic clusters and two laboratory M. tuberculosis strains H37Rv and H37Ra. The virulence was evaluated by the survival of mice after infection and by the trends in body weight loss. The study indicated that the mice inoculated with different M. tuberculosis strains differed in survival rates and in the trend in body weight loss. A minor HD cluster strain and 2 non-clustered strains were most virulent, next were 2 AI cluster strains. W cluster strains had both higher (n = 2) and lower (n = 3), and comparable (n = 2) H37Rv virulence. A KQ cluster strain had the least virulence. An attenuated H37Ra strain caused no animal death. Inoculation with three multidrug-resistant strains belonging to the W cluster (n = 2) and one non-clustered strain demonstrated no relationship of virulence to the sensitivity of a strain to antituberculous agents. The findings argue against the opinion on W cluster M. tuberculosis strains as hypervirulent.

[Mycobacterium tuberculosis strain transmission caused by migratory processes in the Russian Federation (in case of populational migration from the Caucasian Region to Moscow and the Moscow Region)]

The investigation was carried out on 134 M. tuberculosis isolated from 134 patients treated at the Central Research Institute of Tuberculosis, Russian Academy of Medical Sciences. The patients were divided into 2 groups: 1) those who were natives of Moscow and the Moscow Region (MR patients); 2) those who were migrants to the Moscow Region from Azerbaijan, Daghestan, Chechnya, Ingushetia, Karachai-Cherkessia, North Ossetia (the Caucasian Region) (CR patients) who had fallen in the place of birth. Genotyping by the polymorphism of lengths of the restriction fragments containing the insertion sequence IS6110 revealed a genetic diversity of M. tuberculosis strains. The examined M. tuberculosis strains belonged to 13 genotypic families. The W and AI families were prevalent. The family W M. tuberculosis strains isolated from the Caucasians were highly clustered, as confirmed by the overwhelming predominance of the strain variant W148 (19.7%). The spectrum of the strain variants of the W family, and those of the AI family in particular, greatly differed in MR and CR patients. Only one strain variant AI12 occurring both in MR and CR patients was detected. A study of the transmission activity coefficient (TAC) of the families W and AI indicated that the transmission activity of W strains was significantly higher than that of M. tuberculosis strains of the AI family. A comparative analysis of the TAC of M. tuberculosis strains of the AI family demonstrated that the transmission activity of the strains of this family was identical no matter where a patient had fallen ill (1.59 and 1.41% in the Moscow and Caucasian Regions, respectively). Unlike M. tuberculosis strains of the AI family, the TAC of W strains isolated from the patients infected in the Moscow Region (28.17 and 19.05%, respectively), which suggests the more intensive transmission of the pathogen M. tuberculosis of the W family in the Caucasian Region.

[Examining the ex vivo growth in the macrophages of Mycobacterium tuberculosis of various genotypic clusters]

To study the specific features of replication of Mycobacterium tuberculosis (MBT) strains of the W cluster in the macrophages (MP) on the ex vivo model of peritoneal MP of MBT-infected C57B1/6 mice, the authors estimated the viability of 6 antituberculous drug-sensitive MBT strains of the W-cluster from the incorporation of 5,6-[3H]-uracil into the mycobacterial cells and their induced specific MP from the level of LDH. Eight sensitive MBT strains of other genotypes clustered by the restriction fragment length polymorphism (PDRF) IS6110 and 2 laboratory strains M. tuberculosis H37Rv and M. tuberculosis H37Ra were taken as a control. The study indicated that, cultured in vitro, MBT strains belonging to different genotypic clusters differed in the level of 5,6-[3H]-uracil inclusion. When grown in MP, the MBT population of all genotypes showed a diminished viability as compared with that cultured without MP. The MBT clusters of W and AI clusters, unclustered strains, and M. tuberculosis H37Rv displayed a higher inclusion of 5,6-[3H]-uracil and the strains of KQ and HD clusters and M. tuberculosis H37Ra exhibited a significantly lower inclusion of 5,6-[3H]-uracil. W-cluster strains, the unclustered strain R807, and M. tuberculosis H37Rv showed the highest fitness (adaptability when grown in MP). The virulent strain M. tuberculosis H37Rv and avirulent strain M. tuberculosis H37Ra differed in MP viability by almost 5 times. Evaluation of the cytopathogenic effect indicated that the clinical MBT strains led to a specific MP lysis greater than 40%, the highest effect was produced by the MBT strains of the W cluster (more than 93%) and the HD cluster (96.45%). The control laboratory strains M. tuberculosis H37Rv and M. tuberculosis H37Ra contrasted sharply in their induced specific MP lysis (93.35 and 5.93%, respectively).

[The association of tuberculosis with the specificities of the HLA gene DRB1 in different regions of Tuva]

The fact that genetic factors largely determine susceptibility to different diseases, including those of infectious nature is beyond question now. Tuberculosis is not an exception in this respect. HLA genes that determine different immunological phenomena make a certain contribution to tuberculosis susceptibility. This paper presents the results of typing using the polymerase chain reaction from the specificities of the HLA gene DRB1 in patients with pulmonary tuberculosis and healthy individuals in different regions of the Republic of Tuva. The studies in these regions of Tuva have revealed a significant positive association of tuberculosis with the specificities of HLA DRb1 13(6) and HLA DRB1 14(6). Analyzing 14 families of patients with tuberculosis has shown that HLA haplotypes from the sick parents who carry the specificities of HLA DRB1 13 and/or DRb1 14 are more frequently transmitted to sick children than to healthy ones. High morbidity in the indigenous dwellers of the Republic of Tuva may be associated with these specificities of the HLA gene DRB1, which is due to the national peculiarities of the native population of this republic.

[Comparative characterization of molecular and microbiological methods for controlling chemotherapy in new cases of pulmonary tuberculosis]

The purpose of the study was to define a role of molecular genetic techniques in the evaluation of the efficacy of short-term chemotherapy in patients with pulmonary tuberculosis. A total of 203 patients with first detected tuberculosis patients who isolated Mycobacterium tuberculosis (MBT) were examined. Microbiological methods (bacterioscopy and seeding) and polymerase chain reaction (PCR) were used to detect MBT in new cases. During chemotherapy, there was a reduction in the number of positive results of both bacterioscopy and PCR, which serves as a sign of abacillation. Following 2 months of chemotherapy, 50% of the patients with negative bacterioscopy and seeding were found to have MBT DNA. In the patients with negative bacterioscopy and seeding, the results of PCR were also negative by month 6. In a group of patients without bacterial isolation, but with positive sputum tests for MBT DNA, the efficiency of chemotherapy was confirmed by the negative results of PCR. The latter is shown to enhance the sensitivity of bacteriological tests for MBT and to reduce the time of obtaining their results.

[Genotypic characteristics of Mycobacterium tuberculosis strains from the Republic of Tyva]

To determine the genetic heterogenicity of Mycobacterium tuberculosis isolated from patients with tuberculosis from different districts of the Republic of Tyva, 71 M. tuberculosis strains IS6110 according to the polymorphism of restriction fragment lengths were typed; of them 32 strains were spoligotyped. The study could genetically characterize the groups of M. tuberculosis strains circulating among patients with tuberculosis in the Republic of Tyva. There was a predominance of the W family of mycobacteria (60.56%). The spoligotyping permitted identification of M. tuberculosis with the spoligotype Beijing in the Republic of Tyva. The mycobacteria belonging to this spoligotype were prevalent and accounted for 50% of the strains. The high proportion of strains with the unique spoligotype (25%) that have not earlier been encountered in the international database is a specific feature of the Mycobacterium population from the Republic of Tyva.

[Significance of molecular genetic and immunological techniques in risk groups and in children with tuberculosis]

A total of 188 children and adolescents were examined. In all the children, blood Mycobacterium tuberculosis (MBT) DNA was determined by polymerase chain reaction (PCR) and MBT antigens (AG) and antibodies (AB) were by enzyme immunoassay. The studies have shown that it is expedient to concurrently determine MBT DNA and MBT AT in order to identify local forms of tuberculosis in children from risk groups. If the tests are positive, a comprehensive examination for tuberculosis is required; the presence of the syndrome of common disturbances is generally associated with tuberculous infection. When a local form of tuberculosis is excluded, preventive chemotherapy should be performed. Further negative tests for MBT DNA and lower MBT AT may be a criterion for the efficiency of preventive treatment. In children with tuberculosis, the results of repeated blood and urine tests for MBT DNA provide a way of evaluating the course of a tuberculous process and the efficiency of chemotherapy. PCR used to determine blood and urine MBT DNA is a highly specific test as positive results were in 79% of the children with tuberculosis.

[Role of PCR analysis in complex bacteriological studies in phthisiology]

The study was undertaken to assess the role of polymerase chain reaction (PCR) analysis in complex bacteriological studies in diagnosing pulmonary tuberculosis in 197 patients by bacterioscopy, inoculation, and PCR. It was shown that in addition to conventional bacteriological methods, PCR might be used as an additional laboratory study in making a diagnosis in patients with restrictive pulmonary tuberculosis. A combination of cultural inoculation and PCR analysis enhances the sensitivity of bacteriological diagnosis and reduces its duration in oligo- and abacillary patients with tuberculosis. PCR analysis enhances the efficiency of laboratory control over antituberculous chemotherapy.

[Molecular characteristics of multiresistant clinical strains of Mycobacterium tuberculosis isolated in Russia]

The efficiency of tuberculosis control programs is largely determined by methods for rapid diagnosis of the agent. In comparison with the traditional methods, new molecular technologies for characterization of mycobacteria appear to be more promising, because the result can be obtained in almost no time. Sixty-five strains of M. tuberculosis isolated in various regions of Russia were investigated. Drug resistance and strain appurtenance of this sample were determined by classical (absolute concentrations method, IS6110-RFLP) and modern molecular genetic methods (detection of mutations in rpo B gene, DRE-PCR). The spectrum of mutations of the rpoB gene associated with rifampicin resistance was evaluated by direct sequencing. Mutations involving codons 531 (62.7%), 526 (18.6%), and 516 (10.2%) of rpoB gene predominated in the studied sample. The studied strains were discriminated into 52 individual strains by IS6110-RFLP and DRE-PCR typing. Analysis of the resultant genetic variants showed the predominance of M. tuberculosis family W. The efficiency of combined approach to screening for M. tuberculosis is discussed.