[Study on the resistance of rifampicin-resistant Mycobacterium tuberculosis to anti-tuberculosis drugs in group A].

Objective: To summarize the resistance of rifampicin-resistant Mycobacterium tuberculosis to anti-tuberculosis drugs in group A. Methods: In the retrospective study, a total of 1 226 clinical isolates from suspected multidrug-resistant pulmonary tuberculosis patients in Beijing TB control system from 2016 to 2021 were identified as Mycobacterium tuberculosis (MTB) strains by MPB64 antigen detection test. Rifampicin-resistant tuberculosis (RR-TB) strains were screened by the phenotypic drug susceptibility using the proportion method. The drug susceptibilities of Levofloxacin(LFX), Moxifloxacin(MFX), Bedaquiline(BDQ) and Linezolid(LZD)were detected by the phenotypic drug susceptibility with microplate method. The drug resistance rate, drug resistance level and minimum inhibitory concentration (MIC) distribution of four anti-tuberculosis drugs in group A were analyzed. We calculated the demographic distribution of RR-TB, multidrug-resistant tuberculosis(MDR-TB), pre-extensively drug resistant tuberculosis (pre-XDR-TB), extensively drug resistant tuberculosis (XDR-TB) patients and the cross resistance of LFX and MFX, then summarized the drug-resistance spectrum of BDQ-resistant and LZD-resistant strains and the treatment outcome of RR-TB patients. Measurement data were expressed as rate or composition ratio,χ2 test was used between and within groups, and P<0.05 was considered statistically significant. Results: Among the 1 226 suspected multidrug-resistant pulmonary tuberculosis patients, the detection rates of RR/MDR/pre-XDR/XDR-TB patients were 20.8%(255/1 226), 15.2%(186/1 226), 5.7%(70/1 226), 0.5%(6/1 226), respectively. There were statistically significant differences in the distribution of patients with the four types of drug resistance in terms of age and treatment history (χ2=14.95, P=0.020;χ2=15.91, P=0.001). The drug resistance rates of LFX, MFX, BDQ and LZD in RR-TB patients were 27.5% (70/255), 27.5% (70/255), 0.4% (1/255) and 2.4% (6/255), respectively. The MICs of LFX, MFX and LZD-susceptible MTB were mainly at 0.25 mg/L, and the MIC of BDQ-susceptible MTB was mainly concentrated at 0.03 mg/L. 25.1% (64/255) of the RR MTB were resistant to both LFX and MFX, and 6 strains were resistant to LFX or MFX, showing incomplete two-way cross resistance. One BDQ-resistant strain and six LZD-resistant strains were detected. The treatment success rate of RR-TB patients was 74.4% (151/203), and there were statistically significant differences in treatment outcomes between resistant and sensitive patients on the LFX-containing treatment regimen (Fisher's exact test, P=0.012). Conclusions: The prevalence of fluoroquinolones (LFX and MFX) resistance in rifampicin-resistant MTB is very serious. LFX and MFX show incomplete bidirectional cross-resistance. BDQ and LZD have the most promising future in the treatment of MDR-TB. Improve drug-resistance testing will help to further improve the success rate of treatment.

[Analysis of tuberculosis epidemiological characteristics and drug resistance among the floating population in Beijing in 2019].

Objective: To analyze the epidemic characteristics and drug resistance of pulmonary tuberculosis among the floating population in Beijing and to provide a scientific basis for formulating strategies for the prevention and control of tuberculosis among the floating population. Methods: Data of tuberculosis patients who were positive for Mycobacterium tuberculosis culture was collected from 16 districts and one municipal institution of tuberculosis control and prevention in Beijing in 2019. The strain samples were tested for drug sensitivity by the proportional method. According to household registration location, patients were divided into the floating population and Beijing registration. SPSS 19.0 software analyzed tuberculosis patients' epidemic characteristics and drug resistance in the floating population. Results: In 2019, there were 1 171 culture-positive tuberculosis patients in Beijing, among the floating population, 593 (50.64%) patients were identified, with a male-to-female sex ratio of 2.2∶1 (409∶184). Compared to patients under household registration as Beijing residents, a higher proportion of young adults aged 20-39 years (65.09%,386/593) were noticed, with 55.65% (330/593) reported from the urban areas and 96.80% (574/593) were reported the first time. The differences were statistically significant (all P<0.05). After completing the drug sensitivity test, 37 cases were with multiple drug-resistant tuberculosis, accounting for 6.24% (37/593). The rates of isoniazid resistance (42.11%,8/19) and multidrug resistance (21.05%,4/19) in floating population patients after retreatment were significantly higher than those in newly treated patients (11.67%, 67/574 and 5.75%, 33/574), and the differences were statistically significant (all P<0.05). Conclusions: Most patients with tuberculosis in the floating population in Beijing in 2019 were young males aged 20-39 years. The reporting areas were urban areas and the newly treated patients mainly. The patients with tuberculosis in the re-treated floating population were more likely to suffer from multidrug and drug resistance, which should be taken as the key population for prevention and control.

[Distribution and drug resistance of nontuberculous Mycobacteria in Beijing].

Objective: To analyze the distribution and drug resistance of nontuberculous mycobacteria(NTM) in Beijing. Methods: Using PCR-fluorescence probe method we identified 1 552 mycobacterial isolates in 2009 and 1 553 mycobacterial isolates in 2013, which were stored by Beijing Research Institute for Tuberculosis Control.All identified NTM strains were confirmed by 16S rRNA gene sequencing, and drug sensitivity testing was performed by using 1% ratio method.SPSS 13.0 was used for statistical analysis. Results: The isolation rate for NTM in 2009 and 2013 was 3.8%(59/1 552), and 4.6%(71/1 553) respectively. A total of 130 NTM strains were identified to 13 species by 16S rRNA gene sequencing, including M. intracellulare strains 39.2%(51/130), M. kansasii strains 37.7%(49/130), M. avium strains 6.9%(9/130), M. abscessus strains 5.4%(7/130), M. fortuitum strains 3.0%(4/130), M. gordonae strains 1.5%(2/130), M. xenopi strains 1.5%(2/130), M. scrofulaceum, M. Phlei, M. smegmatis, M. vaccae, M. neoaurum, M. kumamotonense 1 strain each. For the patients infected with NTM, 87 were male and 43 were female, with an average age of 55 years. The results of drug sensitivity test from 97 strains of NTM showed that isoniazid and p-aminosalicylic acid showed the highest drug resistant rate of 98%(95/97), followed by streptomycin 94.8%(92/97), capreomycin 81.4%(79/97), amikacin 69.1%(67/97), levofloxacin 56.7%(55/97), rifampicin 54.6%(53/97), prothionamide 51.5%(50/97), and ethambutol 50.5%(49/97). Conclusions:Mycobacterium intracellulare and Mycobacterium kansasii were the main strains isolated from patients infected with NTM in Beijing. Patients infected with NTM were mostly males. NTM showed high resistance to anti-tuberculosis drugs.

Relationship of p15 and p16 gene alterations to elevated dihydrofolate reductase in childhood acute lymphoblastic leukaemia.

The downstream effects of p15 and p16 gene deletions and loss of transcripts on dihydrofolate reductase (DHFR) were examined in 63 B-precursor (BP) acute lymphoblastic leukaemia (ALL) samples. p15 and/or p16 gene deletions were seen in 6% and 8%, respectively, of BP-ALL samples; however, losses of p15 and/or p16 transcripts were seen in 26 out of 63 (41%) samples. Loss of p15 transcripts (36.5%) exceeded that for p16 (17.5%). For the 26 BP-ALLs that lacked p15 and/or p16 transcripts, only six (23%) exhibited low levels of DHFR by flow cytometry assay with Pt430, a fluorescent anti-folate. Conversely, 18 out of 37 (49%) BP-ALL samples with intact p15 and/or p16 genes and transcripts showed low levels of DHFR (P = 0.04). In p15- and p16-null K562 cells transfected with a tetracycline-inducible p15 cDNA construct, induction of p15 transcripts and protein was accompanied by decreased growth rates, decreased S-phase fraction, decreased retinoblastoma protein phosphorylation, and markedly reduced levels of DHFR transcripts and protein. Collectively, our results suggest that losses of p15 and/or p16 gene expression result in elevated levels of DHFR in BP-ALL in children. However, additional downstream factors undoubtedly also contribute to elevated levels of this enzyme target.

Association of deletions and translocation of the reduced folate carrier gene with profound loss of gene expression in methotrexate-resistant K562 human erythroleukemia cells.

Severe impairment of methotrexate membrane transport in methotrexate-resistant K562 (K500E) cells was characterized by a nearly complete loss of reduced folate carrier (RFC) transcripts and RFC protein. As determined by 5'-rapid amplification of cDNA ends (5'-RACE), approximately 93% of the RFC transcripts in wild-type cells contained the KS43 5'-untranslated region transcribed from the RFC-B promoter. KS43 transcripts decreased > 90% in K500E cells. The basal and full-length RFC-B promoters were more active (3- and 2-fold, respectively) in directing transcription of a luciferase reporter gene in K500E than in wild-type cells. Treatment with a demethylating agent, 5-aza-2'-deoxycytidine, or with a histone deacetylase inhibitor, trichostatin A, did not increase the levels of RFC transcripts in K500E cells. No differences in RFC gene structure were detected between the lines on Southern blots; however, the RFC signals were decreased approximately 60% in K500E cells. DNA sequences were identical between the lines for the RFC coding region and the two 5'-non-coding exons and their respective promoters. Spectral karyotype analysis and fluorescence in situ hybridization in wild-type cells showed two normal chromosome 21 copies and one or two marker chromosomes, each with an RFC signal. In K500E cells, the RFC gene locus was no longer localized to a normal chromosome 21 (at 21q22.2), and a single RFC signal was associated with a small metacentric chromosome, characterized by a 21/22 translocation. Our results suggest that loss of RFC transcripts in K500E cells is unrelated to changes in the levels of critical transcription factors, or to differences in the extent of RFC promoter methylation or core histone deacetylation. Rather, this phenotype is due to the loss of one or more RFC alleles, and to a translocation of the remaining RFC allele with the formation of a 21/22 fusion chromosome.

Repression of human reduced folate carrier gene expression by wild type p53.

The relationship between loss of functional p53 and human reduced folate carrier (hRFC) levels and function was examined in REH lymphoblastic leukemia cells, which express wild type p53, and in p53-null K562 cells (K562(pTet-on/p53)) engineered to express wild type p53 under control of a tetracycline-inducible promoter. Activation of p53 in REH cells by treatment with daunorubicin was accompanied by decreased ( approximately 5-fold) levels of hRFC transcripts and methotrexate transport. Treatment of K562(pTet-on/p53) cells with doxycycline resulted in a dose-dependent expression of p53 protein and transcripts, increased p21 protein, decreased dihydrofolate reductase, and G(1) arrest with decreased numbers of cells in S-phase. p53 induction was accompanied by up to 3-fold decreases in hRFC transcripts transcribed from the upstream hRFC-B promoter and similar losses of hRFC protein and methotrexate uptake capacity. Expression of p15 in an analogous inducible system in K562 cells resulted in a nearly identical decrease of S-phase cells and dihydrofolate reductase without effects on hRFC levels or activity. When the hRFC-B promoter was expressed as full-length and basal promoter-luciferase reporter constructs in K562(pTet-on/p53) cells, induction of p53 with doxycycline resulted in a 3-fold loss of promoter activity, which was reversed by cotransfection with a trans-dominant-negative p53. These studies show that wild type p53 acts as a repressor of hRFC gene expression, via a mechanism that is independent of its effects on cell cycle progression.

Comparison of effects of magnesium valproate and sodium valproate on the action potential of isolated papillary muscle from guinea pigs and dogs.

A comparison of the effects of magnesium valproate (MV) and sodium valproate (SV) on the action potential of isolated papillary muscle from guinea pigs and dogs was made in this study. The results in both animals were as follows: MV and SV induced a slight reduction of slope plateau of action potential and prolongation of action potential duration (APD). What is more, APD50 and APD90 were prolonged significantly, thus the ratio of APD90/APD25 was increased. The effective refractory period (ERP) was prolonged significantly. MV or SV showed no effects on action potential amplitude, overshoot, resting potential and phase 0 upstroke velocity. The above results suggested that MV and SV might play an antiarrhythmic role and that their effects were analogic. The mechanism of MV and SV inducing significant prolongation of APD50, APD90, and ERP, might be closely related to the slow-down of the velocity of K+ efflux during plateau and repolarization of phase 3 by radical of valproate and the slow-down of velocity of K+ efflux of repolarization of phase 3 in particular. These results showed that there was no difference in SV and MV action on guinea pigs and dogs.