Dynamic changes of respiratory microbiota associated with treatment outcome in drug-sensitive and drug-resistant pulmonary tuberculosis.

BACKGROUND: Respiratory microbiota is closely related to tuberculosis (TB) initiation and progression. However, the dynamic changes of respiratory microbiota during treatment and its association with TB progression remains unclear. METHODS: A total of 16 healthy individuals and 16 TB patients (10 drug-sensitive TB (DS-TB) and 6 drug-resistant TB (DR-TB)) were recruited. Sputum samples were collected at baseline for all anticipants and after anti-TB treatment at Month-6 for TB patients. High throughput 16 S RNA sequencing was used to characterize the respiratory microbiota composition. RESULTS: Compared to the healthy individuals, TB patients exhibited lower respiratory microbiota diversity (p < 0.05). This disruption was alleviated after anti-TB treatment, especially for DS-TB patients. Parvimonas spp. numbers significantly increased after six months of anti-TB treatment in both DS-TB and DR-TB patients (p < 0.05). Rothia spp. increase during treatment was associated with longer sputum-culture conversion time and worse pulmonary lesion absorption (p < 0.05). Besides, Moraxella spp. prevalence was associated with longer sputum-culture conversion time, while Gemella spp. increase was associated with worsening resolving of pulmonary lesions (p < 0.05). CONCLUSION: Dynamic changes of respiratory microbiota during anti-TB treatment is closely related to TB progression. The involvement of critical microorganisms, such as Parvimonas spp., Rothia spp., Moraxella, and Gemella spp., appears to be associated with pulmonary inflammatory conditions, particularly among DR-TB. These microorganisms could potentially serve as biomarkers or even as targets for therapeutic intervention to enhance the prognosis of tuberculosis patients.

Airway microecology in rifampicin-resistant and rifampicin-sensitive pulmonary tuberculosis patients.

BACKGROUND: Pulmonary tuberculosis is a chronic infectious disease of the respiratory system. It is still one of the leading causes of death from a single infectious disease, but it has been stuck in the study of a single pathogen. Recent studies have shown that many diseases are associated with disruption of the native microbiota. In this study we investigated the occurrence of tuberculosis and the correlation between drug resistance and respiratory flora. High-throughput 16 S rRNA gene sequencing was used to characterize the respiratory microbiota composition of 30 tuberculosis (TB) affected patients and compared with 30 healthy (H) controls. According to their Gene Xpert results, 30 pulmonary tuberculosis patients were divided into 12 persons in the drug-sensitive group (DS0) and 18 persons in the drug-resistant group (DR0). The microbial flora of the two were compared with the H group. RESULTS: The data generated by sequencing showed that Firmicutes, Proteus, Bacteroides, Actinomyces and Fusobacterium were the five main bacterial phyla detected, and they constituted more than 96% of the microbial community. The relative abundances of Fusobacterium, Haemophilus, Porphyromonas, Neisseria, TM7, Spirochetes, SR1, and Tenericutes in the TB group was lower than that of the H group, and Granulicatella was higher than the H group. The PcoA diagrams of the two groups had obvious clustering differences. The Alpha diversity of the TB group was lower than that of the H group, and the Beta diversity was higher than that of the H group (P < 0.05). The relative abundance of Streptococcus in the DS0 group was significantly higher than that in the DR0 group (P < 0.05). CONCLUSION: Pulmonary tuberculosis can cause disorders of the respiratory tract microbial flora, in which the relative abundance of Streptococcus was significantly different between rifampicin-sensitive and rifampicin-resistant patients.

Pyrazinoic Acid Inhibits a Bifunctional Enzyme in Mycobacterium tuberculosis.

Pyrazinamide (PZA), an indispensable component of modern tuberculosis treatment, acts as a key sterilizing drug. While the mechanism of activation of this prodrug into pyrazinoic acid (POA) by Mycobacterium tuberculosis has been extensively studied, not all molecular determinants that confer resistance to this mysterious drug have been identified. Here, we report how a new PZA resistance determinant, the Asp67Asn substitution in Rv2783, confers M. tuberculosis resistance to PZA. Expression of the mutant allele but not the wild-type allele in M. tuberculosis recapitulates the PZA resistance observed in clinical isolates. In addition to catalyzing the metabolism of RNA and single-stranded DNA, Rv2783 also metabolized ppGpp, an important signal transducer involved in the stringent response in bacteria. All catalytic activities of the wild-type Rv2783 but not the mutant were significantly inhibited by POA. These results, which indicate that Rv2783 is a target of PZA, provide new insight into the molecular mechanism of the sterilizing activity of this drug and a basis for improving the molecular diagnosis of PZA resistance and developing evolved PZA derivatives to enhance its antituberculosis activity.

Identification of Lysine Acetylation in Mycobacterium abscessus Using LC-MS/MS after Immunoprecipitation.

Mycobacterium abscessus (MAB), which manifests in the pulmonary system, is one of the neglected causes of nontuberculous mycobacteria (NTM) infection. Treatment against MAB is difficult, characterized by its intrinsic antibiotic drug resistance. Lysine acetylation can alter the physiochemical property of proteins in living organisms. This study aimed to determine if this protein post-translational modification (PTM) exists in a clinical isolate M. abscessus GZ002. We used the antiacetyl-lysine immunoprecipitation to enrich the low-abundant PTM proteins, followed by the LC-MS/MS analysis. The lysine acetylome of M. abscessus GZ002 was determined. There were 459 lysine acetylation sites found in 289 acetylated proteins. Lysine acetylation occurred in 5.87% of the M. abscessus GZ002 proteome, and at least 25% of them were growth essential. Aerobic respiration and carbohydrate metabolic pathways of M. abscessus GZ002 were enriched with lysine acetylation. Through bioinformatics analysis, we identified four major acetyl motif logos (K(ac)Y, K(ac)F, K(ac)H, and DK(ac)). Further comparison of the reported M. tuberculosis (MTB) acetylomes and that of MAB GZ002 revealed several common features between these two species. The lysine residues of several antibiotic-resistance, virulence, and persistence-related proteins were acetylated in both MAB GZ002 and MTB. There were 51 identical acetylation sites in 37 proteins found in common between MAB GZ002 and MTB. Overall, we demonstrate a profile of lysine acetylation in MAB GZ002 proteome that shares similarities with MTB. Interventions that target at these conserved sections may be valuable as anti-NTM or anti-TB therapies.

Role of the Cys154Arg Substitution in Ribosomal Protein L3 in Oxazolidinone Resistance in Mycobacterium tuberculosis.

We expressed the wild-type rplC and mutated rplC (Cys154Arg) genes, respectively, in Mycobacterium tuberculosis H37Ra and H37Rv in an attempt to delineate the role of rplC (Cys154Arg) regarding oxazolidinone resistance. An increase of the MICs of linezolid (LZD) and sutezolid (PNU-100480, PNU) against the recombinant mycobacteria with overexpressed rplC mutation (Cys154Arg) was found, suggesting the rplC gene is a determinant of bacillary susceptibilities to LZD and PNU.

Later emergence of acquired drug resistance and its effect on treatment outcome in patients treated with Standard Short-Course Chemotherapy for tuberculosis.

BACKGROUNDS: The failure of current Standard Short-Course Chemotherapy (SCC) in new and previously treated cases with tuberculosis (TB) was mainly due to drug resistance development. But little is known on the characteristics of acquired drug resistant TB during SCC and its correlation with SCC failure. The objective of the study is to explore the traits of acquired drug resistant TB emergence and evaluate their impacts on treatment outcomes. METHODS: A prospective observational study was performed on newly admitted smear positive pulmonary TB (PTB) cases without drug resistance pretreatment treated with SCC under China's National TB Control Program (NTP) condition from 2008 to 2010. Enrolled cases were followed up through sputum smear, culture and drug susceptibility testing (DST) at the end of 1, 2, and 5 months after treatment initiation. The effect factors of early or late emergence of acquired drug resistant TB , such as acquired drug resistance patterns, the number of acquired resistant drugs and previous treatment history were investigated by multivariate logistic regression; and the impact of acquired drug resistant TB emergence on treatment failure were further evaluated. RESULTS: Among 1671 enrolled new and previously treated cases with SCC, 62 (3.7%) acquired different patterns of drug resistant TB at early period within 2 months or later around 3-5 months of treatment. Previously treated cases were more likely to develop acquired multi-drug resistant TB (MDR-TB) (OR, 3.8; 95%CI, 1.4-10.4; P = 0.015). Additionally, acquired MDR-TB cases were more likely to emerge at later period around 3-5 months after treatment starting than that of non-MDR-TB mainly appeared within 2 months (OR, 8.3; 95%CI, 1.7-39.9; P = 0.008). Treatment failure was associated with late acquired drug resistant TB emergence (OR, 25.7; 95%CI, 4.3-153.4; P < 0.001) with the reference of early acquired drug resistant TB emergence. CONCLUSIONS: This study demonstrates that later development of acquired drug resistant TB during SCC is liable to suffer treatment failure and acquired MDR-TB pattern may be one of the possible causes.

Progress in resistance mechanisms and diagnosis of non-first line anti-TB drugs.

Tuberculosis (TB) is one of the three major infectious diseases in China and all over the world. In 2014, for the first time, TB killed more people than HIV did. Non-first line anti-TB drugs are used as main drugs in the treatment of MDR-TB. However, MDR-TB can gradually develop as extensively drug-resistant TB (XDR-TB) because of poor diagnosis, the unreasonable treatment, poor medical conditions and so on. The death rate of XDR-TB is close to lung cancer. Research on the mechanism of drug resistance of Mycobacterium tuberculosis has turned to non first-line anti-TB drugs: second and third line drugs and some new anti-TB drugs in development. In this review, we summarized the drug resistance mechanisms of the common non-first line anti-TB drugs. Most of drug resistant TB patients can't get timely diagnosis and correct treatment. So at the end of this article, we also summarized the common methods to diagnose drug-resistant TB.

Role of pncA and rpsA gene sequencing in detection of pyrazinamide resistance in Mycobacterium tuberculosis isolates from southern China.

We sequenced pncA and rpsA genes plus flanking regions of 161 Mycobacterium tuberculosis isolates and found 10 new pncA and 3 novel rpsA mutations in pyrazinamide-resistant strains determined by the Bactec MGIT 960 system. The 3' end of rpsA might be added as the target of molecular detection of pyrazinamide susceptibility.

[The therapeutic effect of regimens containing isoniazid and rifampicin for pulmonary tuberculosis with single isoniazid or rifampicin resistance].

OBJECTIVE: To study regimens containing isoniazid and rifampicin for the treatment of pulmonary tuberculosis with isoniazid or rifampicin resistance. METHODS: Eighty patients with isoniazid or rifampicin resistance, and whose sputum were still positive at the end of 2-month therapy with isoniazid (H), rifampicin (R), pyrazineamide (Z) and ethambutol (E), were retrospectively analyzed from Jan.2009 to Dec.2012 in Guangzhou Chest Hospital. According to the Mycobacterium drug sensitive test (DST) before the treatment with isoniazid and rifampicin, the patients were divided into the sensitive group (either H or R sensitive), the multidrug-resistance group (both H and R resistance) and the single-resistance group (H or R resistance). There were 80 patients (57 females, 23 males) whose sputum was still positive at the end of 2 month treatment. Their ages ranged from 16-80 (average 45) years. Among them, 29 received the first-treatment, while 51 received retreatment. There were 37 cases in the sensitive group, with 18 first-treatment patients and 19 retreatment patients. There were 15 cases in the single-resistance group, with 3 first-treatment patients and 12 retreatment patients. There were 28 cases in the multidrug-resistance group, with 8 first-treatment patients and 20 retreatment patients. RESULTS: After treatment, mycobacterial conversion to MDR-TB occurred in 2 patients in the sensitive group, and in 6 patients in the single-resistance group. The rate of conversion to MDR-TB was higher in the single-resistance group than that in the sensitive group (χ² = 12.849, P = 0.000).Six patients with single H resistance converted to MDR-TB and 2 patients with single R resistance converted to MDR-TB (P < 0.05, RR = 18.0). CONCLUSIONS: Single H or R drug-resistance was more common in retreated patients with pulmonary tuberculosis.If regimens containing isoniazid and rifampicin was used to treat patients with single H or R drug-resistance, resistant enlarging effect may appear and lead to MDR-TB. The retreated patients should be monitored as soon as possible for detection of Mycobacterium resistance to H and R, and regimens for H or R-resistance should be used to prevent resistant enlarging effect.

Diabetes mellitus and tuberculosis: pattern of tuberculosis, two-month smear conversion and treatment outcomes in Guangzhou, China.

OBJECTIVE: There is a high burden of both diabetes (DM) and tuberculosis (TB) in China. We evaluated the association between DM and the pattern of disease, 2-month sputum smear conversion and treatment outcomes of patients with TB in Guangzhou, China. METHOD: All patients registered with TB from September 2011 to June 2012 were screened for DM and assessed for treatment outcomes in relation to presence or absence of DM and quality of DM control using patient registers, treatment cards and electronic record systems. RESULTS: There were 1589 patients with TB of whom 189 (12%) had DM. Among those with DM, there was a significantly higher proportion of men, persons aged 35 years and older and persons with smear-positive pulmonary tuberculosis (PTB) (P < 0.01). In patients with DM and new smear-positive PTB, there was a higher proportion who had positive sputum smears at 2 months (21.7% vs. 5.6%, RR 3.85, 95%CI 2.24-6.63), who were lost-to-follow-up (5.2% vs. 1.7%, RR 3.23, 95%CI 1.08-9.63) and who failed treatment (10.3% vs. 2.3%, RR 4.46, 95%CI 1.96-10.18) compared with patients who had no DM. There was no significant association between these adverse outcomes and DM control as measured by 2 and 6-month fasting blood glucose. CONCLUSION: Diabetes mellitus in new smear-positive patients with PTB was associated with failure to sputum smear convert at 2 months and adverse treatment outcomes of loss-to-follow-up and failure. Further research is needed to understand the reasons for these findings and to determine whether the current length of treatment of 6 months is adequate.

[The treatment outcomes of 21 cases of rapidly growing mycobacteria related pulmonary disease].

OBJECTIVE: To explore the efficacy of the chemotherapeutic regimen with clarithromycin (CTM) and amikacin (AMK) as the main drugs in the therapy of rapidly growing mycobacteria (RGM) related pulmonary disease. METHODS: The clinical efficacy of 21 patients with RGM related pulmonary disease was retrospectively analyzed from January 2008 to October 2011 in Guangzhou Chest Hospital. The individual chemotherapeutic regimen was mainly based on azithromycin (ATM) 0.5 g/d or CTM 0.5 - 1.0 g/d, AMK 0.4 - 0.6 g/d according to the medication history and antimicrobial susceptibility tests. After 6 months of treatment, symptomatic improvement, changes of imaging findings, sputum cultures and adverse effects were observed. RESULTS: In the 21 cases of RGM related pulmonary disease, drug resistance to amikacin (9 cases) and clarithromycin (5 cases) were relatively low as compared to other antituberculous drugs. Lesions involving more than 3 lung fields were seen in 17 cases, cough and phlegm in 21, bloody sputum in 18, chest pain and shortness of breath in 15, and fever in 15 cases. After 2-week treatment, fever disappeared and shortness of breath improved in all the cases. Cough and phlegm improved in 12 and bloody sputum improved in 16 cases. After 6-month treatment, lesion absorption occurred in 12 cases, lung cavity became smaller in 9 cases and sputum culture became negative in 8 cases. Of the 16 cases sensitive to CTM, 11 was smear-negative, and of the 12 cases sensitive to AMK, 11 was smear-negative. Common adverse effects included gastrointestinal symptoms, liver damage and blood abnormalities. CONCLUSIONS: Patients with RGM related pulmonary disease had low rates of drug resistance to CTM and AMK. However, individual chemotherapy regimen based on CTM and AMK showed unsatisfactory clinical efficacy. More sensitive drugs combined with potent chemotherapy regimen are needed for the treatment of this disease.

[Comparison of P-nitrobenzoic acid and hydroxylamine hydrochloride for the primary screening of mycobacterial species].

OBJECTIVES: To examine the screening methods for mycobacteria recommended by the China Anti-tuberculosis Association, in order to increase laboratory diagnostic accuracy for mycobacterial screening. METHODS: Using P-nitrobenzoic acid (PNB 0.5 g/L) as the control group, and hydroxylamine hydrochloride (HA, in 125, 150 and 175 mg/L concentrations) as the study group, laboratory preserved strains of H37Rv M.tuberculosis, and standard and clinically isolated strains of M.nontuberculosis (NTM) from Guangzhou Chest Hospital were tested for both PNB and HA sensitivity. Differences between groups were analyzed by χ(2) test. RESULTS: Among the 2529 MTB strains, the resistance rate to PNB was 3.0% (76/2529), to HA was 12.2% (308/2529), 4.8% (121/2529), and 0.9% (23/2529), respectively, corresponding to the aforementioned 3 different concentrations of HA. Among the 1766 NTM strains, the sensitive rate to PNB was 8.3% (147/1766), to HA was 0.1% (2/1766), 0.5% (9/1766), and 0.9% (16/1766), respectively, corresponding to the aforementioned 3 different concentrations of HA. There was significant difference (χ(2) = 5.44-83.50, P < 0.05). CONCLUSION: HA at 175 mg/L concentration was the optimal condition for laboratory tuberculosis preliminary screening.

Molecular mechanisms of resistance and treatment efficacy of clofazimine and bedaquiline against Mycobacterium tuberculosis.

Clofazimine (CFZ) and bedaquiline (BDQ) are currently used for the treatment of multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) strains. In recent years, adding CFZ and BDQ to tuberculosis (TB) drug regimens against MDR Mtb strains has significantly improved treatment results, but these improvements are threatened by the emergence of MDR and extensively drug-resistant (XDR) Mtb strains. Recently, CFZ and BDQ have attracted much attention for their strong clinical efficacy, although very little is known about the mechanisms of action, drug susceptibility test (DST), resistance mechanisms, cross-resistance, and pharmacokinetics of these two drugs. In this current review, we provide recent updates on the mechanisms of action, DST, associated mutations with individual resistance and cross-resistance, clinical efficacy, and pharmacokinetics of CFZ and BDQ against Mtb strains. Presently, known mechanisms of resistance for CFZ and/or BDQ include mutations within the Rv0678, pepQ, Rv1979c, and atpE genes. The cross-resistance between CFZ and BDQ may reduce available MDR-/XDR-TB treatment options. The use of CFZ and BDQ for treatment in the setting of limited DST could allow further spread of drug resistance. The DST and resistance knowledge are urgently needed where CFZ and BDQ resistance do emerge. Therefore, an in-depth understanding of clinical efficacy, DST, cross-resistance, and pharmacokinetics for CFZ and BDQ against Mtb can provide new ideas for improving treatment outcomes, reducing mortality, preventing drug resistance, and TB transmission. Along with this, it will also help to develop rapid molecular diagnostic tools as well as novel therapeutic drugs for TB.

Screening of patients with tuberculosis for diabetes mellitus in China.

OBJECTIVE: There is a high burden of both diabetes (DM) and tuberculosis (TB) in China, and this study aimed to assess feasibility and results of screening patients with TB for DM within the routine healthcare setting of six health facilities. METHOD: Agreement on how to screen, monitor and record was reached in May 2011 at a stakeholders' meeting, and training was carried out for staff in the six facilities in July 2011. Implementation started in September 2011, and we report on 7 months of activities up to 31 March 2012. RESULTS: There were 8886 registered patients with TB. They were first asked whether they had DM. If the answer was no, they were screened with a random blood glucose (RBG) followed by fasting blood glucose (FBG) in those with RBG ≥ 6.1 mm (one facility) or with an initial FBG (five facilities). Those with FBG ≥ 7.0 mm were referred to DM clinics for diagnostic confirmation with a second FBG. Altogether, 1090 (12.4%) patients with DM were identified, of whom 863 (9.7%) had a known diagnosis of DM. Of 8023 patients who needed screening for DM, 7947 (99%) were screened. This resulted in a new diagnosis of DM in 227 patients (2.9% of screened patients), and of these, 226 were enrolled to DM care. In addition, 575 (7.8%) persons had impaired fasting glucose (FBG 6.1 to <7.0 mm). Prevalence of DM was significantly higher in patients in health facilities serving urban populations (14.0%) than rural populations (10.6%) and higher in hospital patients (13.5%) than those attending TB clinics (8.5%). CONCLUSION: This pilot project shows that it is feasible to screen patients with TB for DM in the routine setting, resulting in a high yield of patients with known and newly diagnosed disease. Free blood tests for glucose measurement and integration of TB and DM services may improve the diagnosis and management of dually affected patients.

A recombinant selective drug-resistant M. bovis BCG enhances the bactericidal activity of a second-line anti-tuberculosis regimen.

Drug-resistant tuberculosis (DR-TB) poses a new threat to global health; to improve the treatment outcome, therapeutic vaccines are considered the best chemotherapy adjuvants. Unfortunately, there is no therapeutic vaccine approved against DR-TB. Our study assessed the therapeutic efficacy of a recombinant drug-resistant BCG (RdrBCG) vaccine in DR-TB. We constructed the RdrBCG overexpressing Ag85B and Rv2628 by selecting drug-resistant BCG strains and transformed them with plasmid pEBCG or pIBCG to create RdrBCG-E and RdrBCG-I respectively. Following successful stability testing, we tested the vaccine's safety in severe combined immune deficient (SCID) mice that lack both T and B lymphocytes plus immunoglobulins. Finally, we evaluated the RdrBCG's therapeutic efficacy in BALB/c mice infected with rifampin-resistant M. tuberculosis and treated with a second-line anti-TB regimen. We obtained M. bovis strains which were resistant to several second-line drugs and M. tuberculosis resistant to rifampin. Notably, the exogenously inserted genes were lost in RdrBCG-E but remained stable in the RdrBCG-I both in vitro and in vivo. When administered adjunct to a second-line anti-TB regimen in a murine model of DR-TB, the RdrBCG-I lowered lung M. tuberculosis burden by 1 log10. Furthermore, vaccination with RdrBCG-I adjunct to chemotherapy minimized lung tissue pathology in mice. Most importantly, the RdrBCG-I showed almost the same virulence as its parent BCG Tice strain in SCID mice. Our findings suggested that the RdrBCG-I was stable, safe and effective as a therapeutic vaccine. Hence, the "recombinant" plus "drug-resistant" BCG strategy could be a useful concept for developing therapeutic vaccines against DR-TB.

Comparative Analysis of Whole-Genome and Methylome Profiles of a Smooth and a Rough Mycobacterium abscessus Clinical Strain.

Mycobacterium abscessus is a fast growing Mycobacterium species mainly causing skin and respiratory infections in human. M. abscessus is resistant to numerous drugs, which is a major challenge for the treatment. In this study, we have sequenced the genomes of two clinical M. abscessus strains having rough and smooth morphology, using the single molecule real-time and Illumina HiSeq sequencing technology. In addition, we reported the first comparative methylome profiles of a rough and a smooth M. abscessus clinical strains. The number of N4-methylcytosine (4mC) and N6-methyladenine (6mA) modified bases obtained from smooth phenotype were two-fold and 1.6 fold respectively higher than that of rough phenotype. We have also identified 4 distinct novel motifs in two clinical strains and genes encoding antibiotic-modifying/targeting enzymes and genes associated with intracellular survivability having different methylation patterns. To our knowledge, this is the first report about genome-wide methylation profiles of M. abscessus strains and identification of a natural linear plasmid (15 kb) in this critical pathogen harboring methylated bases. The pan-genome analysis of 25 M. abscessus strains including two clinical strains revealed an open pan genome comprises of 7596 gene clusters. Likewise, structural variation analysis revealed that the genome of rough phenotype strain contains more insertions and deletions than the smooth phenotype and that of the reference strain. A total of 391 single nucleotide variations responsible for the non-synonymous mutations were detected in clinical strains compared to the reference genome. The comparative genomic analysis elucidates the genome plasticity in this emerging pathogen. Furthermore, the detection of genome-wide methylation profiles of M. abscessus clinical strains may provide insight into the significant role of DNA methylation in pathogenicity and drug resistance in this opportunistic pathogen.

Detection of Novel Gene Mutations Associated with Pyrazinamide Resistance in Multidrug-Resistant Mycobacterium tuberculosis Clinical Isolates in Southern China.

OBJECTIVE: Pyrazinamide (PZA) is a cornerstone of modern tuberculosis regimens. This study aimed to investigate the performance of genotypic testing of pncA + upstream region, rpsA, panD, Rv2783c, and clpC1 genes to add insights for more accurate molecular diagnosis of PZA-resistant (R) Mycobacterium tuberculosis. METHODS: Drug susceptibility testing, sequencing analysis of PZA-related genes including the entire operon of pncA (Rv2044c-pncA-Rv2042c) and PZase assay were performed for 448 M. tuberculosis clinical isolates. RESULTS: Our data showed that among 448 M. tuberculosis clinical isolates, 113 were MDR, 195 pre-XDR and 70 XDR TB, while the remaining 70 strains had other combinations of drug-resistance. A total of 60.04% (269/448) M. tuberculosis clinical isolates were resistant to PZA, of which 78/113 were MDR, 119/195 pre-XDR and 29/70 XDR TB strains. PZAR isolates have predominance (83.3%) of Beijing genotype. Genotypic characterization of Rv2044c-pncA-Rv2042c revealed novel nonsynonymous mutations in Rv2044c with negative PZase activity which led to confer PZAR. Compared with phenotypic data, 84.38% (227/269) PZAR strains with mutations in pncA + upstream region exhibited 83.64% sensitivity but the combined evaluation of the mutations in rpsA 2.60% (7/269), panD 1.48% (4/269), Rv2783c 1.11% (3/269) and Rv2044c 0.74% (2/269) increased the sensitivity to 89.59%. Fifty-seven novel mutations were identified in this study. Interestingly, a frameshift deletion (C-114del) in upstream of pncAwt nullified the effect of A-11G mutation and induced positive PZase activity, divergent from five PZase negative A-11G PZAR mutants. Twenty-six PZAR strains having wild-type-sequenced genes with positive or negative PZase suggest the existence of unknown resistance mechanisms. CONCLUSION: Our study revealed that PZAR rate in MDR and pre-XDR TB was markedly higher in southern China. The concomitant evaluation of pncA + UFR, rpsA, panD, Rv2783c, and Rv2044c provides more dependable genotypic results of PZA resistance. Fifty-seven novel mutations/indels in this study may play a vital role as diagnostic markers. The upstream region of pncA and PZase regulation are valuable to explore the unknown mechanism of PZA-resistance.

Prevalence and molecular characterization of amikacin resistance among Mycobacterium tuberculosis clinical isolates from southern China.

OBJECTIVES: Amikacin is the only second-line injectable antituberculosis (anti-TB) drug still recommended for multidrug-resistant tuberculosis (MDR-TB) treatment when a short MDR-TB regimen is designed. Mutations in rrs and eis are reported to be associated with resistance to amikacin. In this study, we investigated the incidence of rrs, eis, tap and whiB7 mutations in amikacin-resistant Mycobacterium tuberculosis clinical isolates to find the proportion of different mutations related to amikacin resistance. METHODS: A total of 395 clinical isolates of M. tuberculosis were used for phenotypic drug susceptibility testing (DST) to 10 drugs with the Löwenstein-Jensen (L-J) method. We sequenced rrs, eis, tap and whiB7 genes in 178 M. tuberculosis clinical isolates (89 amikacin-resistant isolates and 89 of 306 amikacin-susceptible isolates). RESULTS: Our data showed that 22.53% (89/395) M. tuberculosis clinical isolates were resistant to amikacin. Of the 89 amikacin-resistant isolates, 89.89% (80/89) were MDR-TB, of which 12.36% (11/89) were pre-extensively drug-resistant TB (pre-XDR-TB) and 77.53% (69/89) were XDR-TB. The rrs mutations were found in 82% (73/89) in amikacin-resistant M. tuberculosis clinical isolates. The A1401G alteration in the rrs gene was the most dominant mutation (80.90%; 72/89). Five mutations were detected as new in rrs, tap and whiB7. Notably, 13.48% (12/89) amikacin-resistant isolates had no known mutation in these genes. CONCLUSIONS: Our data reveal that the rrs mutation is a predominant molecular marker of amikacin resistance in southern China. Analysis of the rrs gene mutations will significantly reduce the time and cost to diagnose amikacin resistance in TB patients. Other unknown amikacin resistance mechanism(s) exist.

Phenotypic and Genotypic Characterization of Streptomycin-Resistant Multidrug-Resistant Mycobacterium tuberculosis Clinical Isolates in Southern China.

Streptomycin (STR) is the first antibiotic used in the treatment of tuberculosis (TB) and the earliest antituberculosis drug with acquired resistance developed by Mycobacterium tuberculosis. The high prevalence of such resistance in many parts of the world limits its use for treating multidrug-resistant (MDR) TB. The aims of this study are to characterize of mutations in rpsL, rrs, and gidB genes in MDR M. tuberculosis isolates originating from southern China and to investigate possible relationship between mutations and strain genotypes for precise diagnosis and treatment. Sequences of rpsL, rrs, and gidB genes and the resistance profiles were analyzed for 218 MDR M. tuberculosis isolates. Our study showed that 68.35% of MDR M. tuberculosis isolates were resistant to STR and 89.91% of STR-resistant (STRR) isolates were Beijing lineage strains. Mutations were observed in STRR MDR M. tuberculosis isolates at the following rates: 72.48% in rpsL, 36.91% in rrs, and 15.44% in gidB. Compared with the phenotypic data, the combination of mutations in rpsL, rrs, and gidB has sensitivity and specificity of 96.64% and 100.00%, respectively. The most common mutations in STRR isolates were rpsL128,263 and rrs514,1401, of which rpsL128 showed association with Beijing lineage (p < 0.001). It is noteworthy that a1401g mutation was present in rrs, while MDR M. tuberculosis isolates were resistant to both STR and amikacin. Twenty two novel mutations were found in STRR isolates. These findings could be helpful to develop rapid molecular diagnostic methods and understand STR resistance in China for developing TB precision medicine and disturbance of drug-resistant TB transmission.

Phenotypic and genotypic characterization of levofloxacin- and moxifloxacin-resistant Mycobacterium tuberculosis clinical isolates in southern China.

BACKGROUND: Levofloxacin (LVX) and Moxifloxacin (MXF) are the cornerstones for treatment of multidrug-resistant tuberculosis (MDR-TB). China is one of the highest MDR- and fluoroquinolones (FQ)-resistant TB burdens countries. DNA gyrase encoded by gyr genes is the main target of FQ in Mycobacterium tuberculosis (MTB). The prevalence and molecular characterization of LVX- and MXF-resistant MTB strains from southern China were examined in this study. METHODS: Drug susceptibility testing (DST) of 400 MTB clinical isolates was evaluated by proportion method on Löwenstein-Jensen (LJ) medium against ten drugs. The sequencing of entire gyrA and gyrB genes and multiplex PCR were performed to distinguish the prevalence of mutant types in Beijing and non-Beijing genotypes. RESULTS: Three hundred and twenty-one out of four hundred (80.25%) drug-resistant isolates (resistant > one drug) were categorized as 83/321 (25.80%) MDR, 174/321 (54.20%) pre-XDR and 64/321 (19.93%) XDR-MTB. Overall, 303/400 (75.75%) LVX- and 292/400 (73.00%) MXF-resistant (R) MTB strains were identified. Two hundred seventy-one out of three hundred and three (89.43%) resistant strains carried mutations in gyrA and 91/303 (30.03%) in gyrB. Interestingly, 18 novel mutations were detected in gyrA and gyrB genes. Mutations at (A90, D94) and (T500, G510, G512) frequently existed in QRDR(s) of gyrA and gyrB respectively in 286/400 (71.50%) LVXRMXFR strains. The novel mutations in- and out-side the QRDR of gyrA (L105R, A126E, M127K, D151T, V165A) and gyrB (D461H, N499S, G520A) increased the sensitivity and consistency of genotypic tests. Notably, 25 LVXRMXFR strains were found with unknown resistance mechanisms. CONCLUSIONS: Mutations in QRDR(s) were concomitantly associated with Beijing and non-Beijing genotypes. The prevalence of resistance and cross-resistance between LVX and MXF in MTB isolates from southern China was immensely higher than other countries. Our valuable findings provide the substantial implications to improve the reliability of genotypic diagnostic tests relying on potential resistance conferring mutations in entire gyr genes.