In Vitro Activity of PBTZ169 against Multiple Mycobacterium Species.

In this study, we demonstrate that PBTZ169 exhibits significant differences in in vitro activity against multiple Mycobacterium species. The amino acid polymorphism at codon 387 of decaprenylphosphoryl-beta-d-ribose oxidase (DprE1) can be used as a surrogate marker for in vitro susceptibility to PBTZ169 in mycobacteria. In addition, the amino acid substitution at codon 154 in DprE1 may be associated with acquired resistance to PBTZ169 in the Mycobacterium fortuitum mutants.

In Vitro Drug Susceptibility of Bedaquiline, Delamanid, Linezolid, Clofazimine, Moxifloxacin, and Gatifloxacin against Extensively Drug-Resistant Tuberculosis in Beijing, China.

Extensively drug-resistant tuberculosis (XDR-TB) is a deadly form of TB that can be incurable due to its extreme drug resistance. In this study, we aimed to explore the in vitro susceptibility to bedaquiline (BDQ), delamanid (DMD), linezolid (LZD), clofazimine (CLO), moxifloxacin (MFX), and gatifloxacin (GAT) of 90 XDR-TB strains isolated from patients in China. We also describe the genetic characteristics of XDR-TB isolates with acquired drug resistance. Resistance to MFX, GAT, LZD, CLO, DMD, and BDQ was found in 82 (91.1%), 76 (84.4%), 5 (5.6%), 5 (5.6%), 4 (4.4%), and 3 (3.3%) isolates among the XDR-TB strains, respectively. The most frequent mutations conferring fluoroquinolone resistance occurred in codon 94 of the gyrA gene (57.8%), and the strains with these mutations (69.2%) were associated with high-level MFX resistance compared to strains with mutations in codon 90 (25.0%) (P < 0.01). All 5 CLO-resistant isolates exhibited ≥4-fold upward shifts in the BDQ MIC, which were attributed to mutations of codons 53 (60.0%) and 157 (20.0%) in the Rv0678 gene. Additionally, mutation in codon 318 of the fbiC gene was identified as the sole mutation related to DMD resistance. In conclusion, our data demonstrate that the XDR-TB strains exhibit a strikingly high proportion of resistance to the current anti-TB drugs, whereas BDQ, DMD, LZD, and CLO exhibit excellent in vitro activity against XDR-TB in the National Clinical Center on TB of China. The extensive cross-resistance between OFX and later-generation fluoroquinolones indicates that MFX and GAT may have difficulty in producing the desired effect for XDR-TB patients.

Probiotic Lactobacillus casei Zhang reduces pro-inflammatory cytokine production and hepatic inflammation in a rat model of acute liver failure.

PURPOSE: In this study, we sought to find the effects and mechanisms of probiotic Lactobacillus casei Zhang (L. casei Zhang) on the pro-inflammatory cytokine production and hepatic inflammatory response in a rat model of acute liver failure induced by lipopolysaccharide (LPS) and d-galactosamine (GalN). METHODS: Male Wistar rats were orally administrated with or without L. casei Zhang for 30 days prior to challenge with LPS and GalN. Dexamethasone administrated group serving as a positive anti-inflammation control. Serum, intestinal and liver samples were collected 8 h after LPS/GalN challenge for histological, molecular and biochemical analysis. RESULTS: LPS/GalN challenge alone resulted in significantly increased production of endotoxin, tumor necrosis factor-α (TNF-α), interleukin-1 beta (IL-1ß) and nitric oxide as compared to the normal control rats. Pretreatment with L. casei Zhang not only reduced these changes, but also attenuated hepatic inflammation as shown by improved histological assessment, decreased myeloperoxidase activity and reduced expression of IL-1ß and inducible nitric oxide synthase in the liver. L. casei Zhang supplementation significantly inhibited LPS/GalN-triggered phosphorylation of ERK, JNK and p-38 MAPK, but increased the expression of TLR2, TLR9 and PPAR-γ. Moreover, L. casei Zhang treatment prevented intestinal injury and modulated the intestinal ecology by increasing the fecal Lactobacillus and Bifidobacterium levels. CONCLUSIONS: Probiotic L. casei Zhang reduces LPS/GalN-induced pro-inflammatory cytokine and hepatic inflammation through modulating the TLR-MAPK-PPAR-γ signaling pathways and intestinal microbiota.

Probiotic Lactobacillus casei Zhang ameliorates high-fructose-induced impaired glucose tolerance in hyperinsulinemia rats.

AIM: To evaluate the preventive and therapeutic effects of Lactobacilluscasei Zhang on impaired glucose tolerance (IGT) by using fructose-induced hyperinsulinemia rats. METHODS: Rats were fed 25 % fructose solution for hyperinsulinemia with L.casei Zhang for prevention or therapy. Serum levels of insulin, glucagon-like peptide-2 (GLP-2), osteocalcin, malondialdehyde (MDA), total intestinal bile acids and hepatic glycogen contents were determined by assay kits. The major bacteria from feces and liver expression of adiponectin receptor 2 (AdipoR2), liver X receptor-α (LXR-α), peroxisome proliferator-activated receptor gamma (PPAR-γ) and vitamin K epoxide reductase complex subunit 1 mRNA were assessed by RT-PCR. Pancreas injury was evaluated by histological analysis. RESULTS: Lactobacilluscasei Zhang significantly increased numbers of Lactobacillus and Bifidobacterium and decreased Clostridium in the intestine (p < 0.01). Meanwhile, liver glycogen contents were significantly decreased (p < 0.05). In preventive group, accompanied by significantly lower insulin and GLP-2 levels (p < 0.05), L.casei Zhang prevented rats from an increase in oral glucose tolerance area under curve (AUC) which was significant in hyperinsulinemia group (p < 0.05). In therapeutic group, L.casei Zhang administration possessed improved glucose tolerance (p < 0.05), which were associated with increased osteocalcin level (p < 0.01), improved intestinal bile acids secretion (p = 0.060), decreased serum MDA levels (p < 0.05) and upregulation of LXR-α, PPAR-γ and AdipoR2 gene expression, as well as an increase in Bacteroides fragilis (p < 0.05). CONCLUSIONS: Lactobacilluscasei Zhang administration exert both preventive and ameliorative effect on oral glucose tolerance AUC in IGT rats but may be via different mechanisms. L.casei Zhang could prevent rats from increased AUC through GLP-2 lowering, while the ameliorative effect in high-fructose-fed post-adolescent rats may be via B. fragilis enriched vitamin K2-dependent osteocalcin mechanism in which AdipoR2, LXR-α and PPAR-γ signaling were involved.

An early and trustable indicator suggestive of non-tuberculosis mycobacteria isolation in a high tuberculosis burden setting.

BACKGROUND: Distinguishing between nontuberculous mycobacterial (NTM) lung infections and pulmonary tuberculosis becomes challenging due to their similar clinical manifestations and radiological images. Consequently, instances of delayed diagnosis or misdiagnosis are highly frequent. A feasible and reliable indicator of the existence of NTM in the early stages of the disease would help to solve this dilemma. METHODS: In this study, we evaluated the potential of smear-positive and Xpert assay (Cepheid, USA) negative outcomes as an early indicator of possible NTM infection in a high TB-burden setting retrospectively and prospectively. RESULTS: During the study period, 12·77% (138/1081) of the smear-positive cases yielded negative outcomes with the simultaneous Xpert assay. From the 110 patients who yielded smear-positive/Xpert-negative outcomes and cultivated strain as well, 105 (95·45%) were proved to have NTM isolated. By incorporating an additional criterion of a negative result from the Interferon-gamma release assay, the accuracy of the screening method reached 100%. Regarding the NTM presence prediction value, smear-positive/Xpert-negative has a sensitivity of 24·86% (45/181) in all NTM isolated cases but 93·75-96·55% accuracy in retrospective study or 93·75% accuracy in prospective study in smear-positive NTM isolated cases. In addition, the specificity was ∼99·47% (943/948) in smear-positive tuberculosis cases. CONCLUSION: The clue of the presence of NTM could be obtained on the first day of the hospital visit due to the point of care (POC) feature of smear testing and Xpert assay. About one-fourth of the NTM-isolated patients would benefit from this rapid, convenient, and reliable screening strategy in the given circumstance. Smear-positive/Xpert-negative outcome is an early, trustable indicator that is indicative of NTM isolation.

Lactobacillus casei Zhang modulate cytokine and toll-like receptor expression and beneficially regulate poly I:C-induced immune responses in RAW264.7 macrophages.

Lactobacilli are frequently used as probiotics due to their beneficial effects on health. Lactobacillus casei Zhang (LcZ), which has favorable probiotic properties, was first isolated from koumiss. In this study, the immunomodulating effects of LcZ on cytokine and toll-like receptor expression in RAW264.7 macrophages was assessed and it was found that live LcZ promotes production of nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-6 and interferon (IFN)-ß. Transcription of inducible nitric oxide synthase (iNOS) was also enhanced by viable LcZ. The immunostimulating effects of live LcZ are significantly attenuated in heat-killed LcZ. Live LcZ promotes TLR2 mRNA transcription, whereas heat-killed LcZ enhances transcription of TLR2, TLR3, TLR4 and TLR9. Furthermore, live LcZ significantly suppresses polyinosinic:polycytidylic acid (poly I:C)-stimulated NO, iNOS and TNF-α expression while enhancing expression of IFN-ß. It was also found that poly I:C-induced interferon regulatory factor 3 (IRF-3) reporter gene activity was significantly up-regulated by live LcZ. These results suggest that LcZ keeps the innate immune system alert by increasing transcription of Toll-like receptors and enhancing production of pro-inflammatory mediators and type I IFN in macrophages. The synergistic effect of live LcZ with poly I:C on IFN-ß expression is associated with increased activity of IRF-3. LcZ has the potential to be used as an adjuvant against viral infections.

Diagnostic Yield of Oral Swab Testing by TB-LAMP for Diagnosis of Pulmonary Tuberculosis.

OBJECTIVE: A prospective study was conducted to ascertain the accuracy of oral swab specimens collected in the early morning, spot and at night for detecting pulmonary tuberculosis (TB). METHODS: We prospectively enrolled patients with symptoms suggestive of pulmonary TB in Beijing Chest Hospital. An early morning sputum specimen was collected from each patient for GeneXpert MTB/RIF (Xpert) and mycobacterial culture. In addition, three oral swabs were collected for TB-LAMP testing. RESULTS: With the combined results of three oral swab specimens, the proportion of Mycobacterium tuberculosis (MTB)-positive cases achieved 40.6%, which was comparable to results for Xpert and MGIT (P=0.603). Using Xpert plus MGIT as reference, the sensitivity of OS-LAMP on a single specimen ranged from 32.6% on the night oral swab to 50.0% on the morning swab. The combination of three oral swab specimens correctly identified 38 MTB-positive cases, indicating an overall sensitivity of 82.6%, which was significantly higher than that of a single oral swab specimen (P<0.001, P=0.001). CONCLUSION: Oral swab can be used as an alternative specimen for diagnosis of pulmonary TB using TB-LAMP. Morning oral swab exhibits the highest sensitivity, and the inclusion of more specimens at different time points provides compensation in diagnostic sensitivity with single oral swab.

Assessment of current diagnostic algorithm for detection of mixed infection with Mycobacterium tuberculosis and nontuberculous mycobacteria.

BACKGROUND: The increasing pulmonary diseases are reported to be affected by mixed infection of Mycobacterium tuberculosis (MTB) and nontuberculous mycobacteria (NTM). In this study, our objective was to assess the efficiency of mycobacterial culture plus DNA sequencing to detect the mixed infections with MTB and various NTM organisms. We also aimed to investigate how efficiently GeneXpert detected MTB in mixed infections with NTM in in vitro models. METHODS: A serial of mixed infection samples was generated by combining suspensions of MTB and five NTM bacteria, respectively. The mixed suspensions were further detected with GeneXpert and liquid culture plus DNA sequencing. RESULTS: Overall, the GeneXpert assay exhibited promising capability to identify the presence of MTB at different proportions ranging from 1% to 99%. For the liquid culture, the subsequent DNA sequencing only detected the presence of NTM bacteria in the mixed samples, which the proportion of NTM ranged from 1% to 99%, including M. intracellulare, M. kansasii, M. abscessus, and M. fortuitum. For M. avium, DNA sequencing was able to identify the mixtures as M. avium infection in suspensions with no less than 10% M. avium bacteria, whereas only MTB was found in the other suspensions with less M. avium bacteria. CONCLUSIONS: Our data demonstrate that the current diagnostic algorithm cannot yield a precise detection of mixed infections with MTB and NTM bacteria. The GeneXpert assay only identify MTB in the mixed samples, while the subculture plus DNA sequencing prefers to identify the NTM species with the higher growth rate. Further targeted molecular analysis by specific capture of multiple loci of mycobacterial species from specimens is urgently required to solve this diagnostic dilemma.

Increased prevalence of levofloxacin-resistant Mycobacterium tuberculosis in China is associated with specific mutations within the gyrA gene.

OBJECTIVES: To compare the prevalence of levofloxacin (LFX) resistance and the population structure of Mycobacterium tuberculosis (MTB) with different mutations conferring LFX resistance between 2005 and 2015. METHODS: A total 542 MTB isolates were randomly selected from pulmonary tuberculosis (TB) patients in 2005 and 2015 and analyzed regarding minimum inhibitory concentrations (MICs) and quinolone resistance-determining regions (QRDR). RESULTS: One hundred and eleven of the 542 MTB isolates analyzed (20.5%) were resistant to LFX. There were 42 and 69 LFX-resistant isolates from 2005 and 2015, respectively, and MIC high-level LFX resistance was significantly higher in 2015 (40.6%, 28/69) than in 2005 (16.7%, 7/42) (p = 0.02). There were 87 (78.4%) mutations of these 111 LFX-resistant isolates. In addition, a significant difference in proportion was observed in the isolates with mutations in codon 90 of the gyrA gene between 2005 and 2015 (11.9% in 2005 versus 29.0% in 2015, p = 0.04). CONCLUSIONS: There was an alarming increase in prevalence of LFX-resistant TB in China between 2005 and 2015. This dynamic change is mostly attributed to the increase in high-level LFX resistance. Moreover, a significant difference was noted in the proportion of LFX-resistant isolates harboring specific mutations within the gyrA gene between 2005 and 2015.

Comparison of Lowenstein-Jensen medium and MGIT culture system for recovery of Mycobacterium tuberculosis from abscess samples.

PURPOSE: In this study, our aim was to assess Lowenstein-Jensen (L-J) medium and MGIT culture system for recovery of Mycobacterium tuberculosis (MTB) from abscess samples in skeletal tuberculosis (TB) cases. METHODS: Abscess samples were collected from patients suggestive of skeletal TB in Beijing Chest Hospital for laboratory examination, including smear microscopy, L-J culture and MGIT culture. RESULTS: Of the 232 abscess samples, 72 (31.0%) were culture-positive for mycobacteria. Of 72 isolates recovered, 94.4% were detected in MGIT 960 and 75.0% on L-J medium. MGIT could recover significantly higher rate of MTB isolates from smear-positive specimens than L-J medium. The mean time to detection of MTB in MGIT 960 was significantly lower than that on L-J medium. CONCLUSION: The BACTEC MGIT 960 outperforms the conventional L-J medium in recovering MTB from abscess samples. The combination of MGIT and L-J method also increases the overall recovery rate of MTB in culture.

Specific gyrA Gene Mutations Correlate with High Prevalence of Discordant Levofloxacin Resistance in Mycobacterium tuberculosis Isolates from Beijing, China.

Although rapid, highly sensitive molecular diagnostics tests are useful for diagnosing fluoroquinolone-resistant tuberculosis (TB), results of molecular testing versus conventional sequential phenotypic drug susceptibility testing (pDST) are frequently discordant. This article determined the discordance rate of levofloxacin (LFX) resistance results, obtained via MeltPro TB molecular testing, versus pDST of clinical TB isolates collected in Beijing, China, between January and December 2018. Isolates with discordant results were further subjected to LFX minimal inhibitory concentration (MIC) determinations and DNA sequence analysis to explore causes of discordance. Of 571 total TB cases, 126 (22.1%) were identified as LFX resistant using the MeltPro TB assay. However, 34 of these 126 LFX-resistant isolates yielded LFX-susceptible test results using pDST, for an overall discordance rate of 27.0%. LFX MICs mainly clustered around the critical LFX concentration, with 7 (21.2%) and 13 (39.4%) of isolates exhibiting MICs of 2.0 and 4.0 mg/L, respectively. The most prevalent LFX resistance mutations associated with discordant results were involved in DNA gyrase subunit A amino acid substitutions Ala90Val (13, 39.4%) and Asp94Ala (11, 33.3%). Notably, more than one-quarter of isolates deemed LFX resistant via the MeltPro assay were scored as LFX susceptible on the basis of pDST results. Ultimately, highly discordant LFX-resistance test results were associated with specific gyrA mutations in isolates with MICs approaching the critical LFX concentration.

Multicenter evaluation of the acid-fast bacillus smear, mycobacterial culture, Xpert MTB/RIF assay, and adenosine deaminase for the diagnosis of tuberculous peritonitis in China.

BACKGROUND: The aim of this study was to assess the validity of GeneXpert MTB/RIF (Xpert) and adenosine deaminase (ADA) in the diagnosis of tuberculous peritonitis (TBP). METHODS: The laboratory results of peritoneal effusion (PE) specimens from patients with symptoms suggestive of TBP, attending three TB specialized hospitals between January 2016 and December 2018, were included retrospectively. Clinically diagnosed TBP was set as the gold standard to evaluate the performance of these methods. RESULTS: In total, 191 individuals presenting with symptoms suggestive of TBP were included for analysis. The sensitivities of MGIT culture and Xpert were 17.2% and 18.3%, respectively. In addition, the TBP cases (69.8±6.0U/l) had higher amounts of ADA in their PE samples than the non-TBP cases (12.6±1.6U/l; p<0.01). Using a threshold of 31.5U/l to differentiate the TBP group from non-TBP group, the ADA assay provided a sensitivity of 89.6% and a specificity of 92.1%. The mean ADA concentration was significantly higher in bacteria-positive cases than in bacteria-negative cases (p<0.01). CONCLUSIONS: In conclusion, the study data demonstrate the high sensitivity and specificity of the ADA test for the early diagnosis of TBP. In addition, the ADA concentration is directly correlated with the mycobacterial load.

No in vitro synergistic effect of bedaquiline combined with fluoroquinolones, linezolid, and clofazimine against extensively drug-resistant tuberculosis.

PURPOSE: We explored the potential synergistic effect of bedaquiline (BDQ) combined with moxifloxacin (MFX), gatifloxacin (GAT), clofazimine (CLO), and linezolid (LZD) for treatment of extensively drug-resistant tuberculosis (XDR-TB). METHODS: Of 191 XDR-TB isolates, 20 exhibiting minimal inhibitory concentration (MIC) values ≥0.063 µg/mL for BDQ were selected to study potential synergistic, additive, or antagonistic drug effects using a checkerboard assay. RESULTS: Antagonism occurred in 14 (70.0%), 0 (0.0%), 13 (65.0%), and 4 (20.0%) XDR-TB isolates for BDQ-MFX, BDQ-GAT, BDQ-LZD, and BDQ-CLO combinations, respectively. CONCLUSION: Our in vitro data demonstrate no observed synergistic effects against XDR-TB for drug combinations that included BDQ in combination with MFX, GAT, LZD, or CLO.

Transdermal delivery of isoniazid and rifampin in guinea pigs by electro-phonophoresis.

Electro-phonophoresis (EP) has been used as a drug delivery approach in clinical fields. The objective of the present study is to evaluate the skin permeability of isoniazid and rifampin in guinea pigs by EP to provide reference basis for clinical applications of such transdermal delivery system in the treatment of patients with superficial tuberculosis. Isoniazid and rifampin solutions were delivered transdermally with or without EP in health guinea pigs for 0.5 h. Local skin and blood samples were collected serially at 0, 1/2, 1, 2, 4, 6 and 24 h after dosing. Drug concentrations in local skin and blood were evaluated by high-performance liquid chromatography. Isoniazid concentrations in local skin of guinea pigs receiving isoniazid through EP transdermal delivery were significantly higher than in animals receiving only isoniazid with transdermal patch. However, for rifampin, patches alone group presented almost uniform concentration versus time curve with that of EP group, and both groups had concentrations much higher than the therapeutic concentration of the drug over sustainable time. After EP transdermal delivery, the mean peak concentrations of isoniazid and rifampin in skin were 771.0 ± 163.4 µg/mL and 81.2 ± 17.3 µg/mL respectively. Neither isoniazid nor rifampin concentration in blood could be detected (below the lower detection limit of 1 µg/mL) at any time point. The present study showed that application of EP significantly enhanced INH penetration through skin in guinea pigs, while RIF patch alone obtained therapeutic concentration in local skin. Our work suggests several possible medication approaches for efficient treatment of superficial tuberculosis.

GeneXpert MTB/RIF assay in the diagnosis of urinary tuberculosis from urine specimens.

Conventional bacteriological methods are not generally helpful in diagnosing urinary tuberculosis (UTB). GeneXpert is endorsed for the detection of pulmonary tuberculosis, whereas the data on its utility for urine specimens is limited. In this study, we aimed to evaluate its performance on urine specimens in a country with high TB incidence. A total of 163 suspected UTB patients were consecutively enrolled in the analysis, including 37 (22.7%) culture-positive and 44 (27.0%) clinically diagnosed UTB cases. Compared with conventional culture, the sensitivity of GeneXpert (94.6%) was significantly higher than that of smear microscopy (40.5%, P < 0.001). When setting clinical diagnosis as gold standard, 51 out of 81 clinically diagnosed UTB cases were detected by GeneXpert, demonstrating a sensitivity of 63.0%, which was significantly higher than that of smear microscopy (18.5%, P < 0.001) and culture (45.7%, P = 0.027), respectively. In addition, the proportion of UTB cases in the migrant population was significantly higher than that in the resident population (P = 0.019). To conclude, our data demonstrate that GeneXpert outperforms AFB smear and culture for the detection of MTB in urine samples, which provides an alternative for the diagnosis of UTB. The migrant population and previously diagnosed TB cases are high risk factors for developing UTB cases.

Prevalence and treatment outcome of extensively drug-resistant tuberculosis plus additional drug resistance from the National Clinical Center for Tuberculosis in China: A five-year review.

OBJECTIVES: The objective of this study was to explore the prevalence and primary clinical outcomes of extensively drug-resistant tuberculosis plus addition resistance to all drug tested (XDR-TB-Plus) between 2011 and 2015 in Beijing Chest Hospital. METHODS: We retrospectively reviewed the drug susceptibility testing (DST) results of clinical Mycobacterium tuberculosis (MTB) strains from TB patients seeking health care in the National Clinical Center for Tuberculosis, between 2011 and 2015. The medical records of patients classified as XDR-TB-Plus were reviewed, including demographic characteristics, treatment regimen, and treatment outcome. RESULTS: Of 9544 MTB isolates, there were 3376 (35.4%), 842 (8.8%) and 61 (0.64%) isolates identified as multidrug resistant tuberculosis (MDR-TB), extensively drug resistant tuberculosis (XDR-TB) and XDR-TB-Plus, respectively. The proportion of XDR-TB showed significant increase from 6.3% in 2011 to 9.1% in 2015 (Chi-square trend 5.94, P = 0.015). Similarly, the proportion of XDR-TB-Plus seemed to increase from 0.46% in 2011 to 0.74% in 2015, while the increasing trend was not significant (Chi-square trend 1.50, P = 0.221). The most frequently prescribed anti-TB drug was moxifloxacin (18/29, 62.1%), followed by protionamide (16/29, 55.2%), clofazimine (15/29, 51.7%), and pyrazinamide (15/29, 51.7%). Patients receiving regimens containing linezolid (LZD) were almost 27 times more likely to have favorable treatment outcome compared with those receiving regimens without LZD [odds ratios = 27.00; 95% CI = 2.50-291.19; P = 0.003]. CONCLUSIONS: In conclusion, our data have demonstrated that the proportion of XDR-TB has significantly increased over the past five years in Beijing Chest Hospital. In addition, the XDR-TB-Plus patients were more likely to reach favorable clinical outcome under the treatment of regimen containing LZD.

The reliability analysis of Xpert-positive result for smear-negative and culture-negative specimen collected from bone and joint tuberculosis suspects.

BACKGROUND: The Xpert MTB/RIF assay (Xpert; Cepheid, Sunnyvale, CA, USA) has been widely used for pulmonary and extra-pulmonary tuberculosis (TB) diagnosis. In clinical practice, specimen yielding smear-negative, culture-negative but Xpert-positive results is frequently confronted. Due to the notorious possibility of contamination that molecular tests always been thought of, Xpert-positive results without bacteriological supporting evidence arouse great confusions to clinicians. METHODS: A retrospective study was performed. From April 2014 to February 2015, 852 clinical specimens were Xpert-positive. The results of Xpert assay, bacteriological and pathological examinations from either the same specimens or from the specimens collected during same clinical operations were investigated. RESULTS: A total of 90 specimens with Xpert-positive but smear-negative and culture-negative results were recruited, and 81 of them were pus specimens collected from Bone and Joint Tuberculosis (BJTB) patients. According to the pathological examination results, 77 of the 81 pus specimens, 8 of 9 other types of specimens were confirmed as either TB or strongly suggestive of TB; three pus specimens and one biopsy tissue were also suggested TB but with less stronger evidence; only one pus specimen was not TB suggestive. CONCLUSIONS: Our study demonstrated that Xpert could be trusted for BJTB diagnosis even when no supporting bacteriological evidence is available in high TB prevalence settings. Our results will alleviate the confusion among clinicians in such scenarios.

Rapid identification of the NAT2 genotype in tuberculosis patients by multicolor melting curve analysis.

AIM: NAT2 genotype is an indicator for isoniazid dosage adjusting for tuberculosis treatment. Multicolor melting curve analysis (MMCA) was evaluated as a potential method for NAT2 genotyping. MATERIALS & METHODS: 352 blood samples were analyzed by MMCA kit (Zeesan Biotech Co., Xiamen, China) targeting NAT2 SNPs at T341C, C481T, G590A and G857A, and direct sequencing was used as control. RESULTS: The sensitivity, specificity and accuracy of the MMCA assay for rapid NAT2 genotype detection were 97.9, 99.6 and 99.1% respectively, whereas for intermediate genotypes the values were 99.5, 98.7 and 99.1%, respectively, and for slow genotypes the values were 100% for the three aspects. The 24 saliva and blood for the control samples were also successfully analyzed using the MMCA assay, both produced uniform outcomes. CONCLUSION: The MMCA assay described in our study is very promising for the efficient determination of NAT2 genotype, and can facilitate the personalized dosing of isoniazid.

Pyrazinamide resistance among multidrug-resistant tuberculosis clinical isolates in a national referral center of China and its correlations with pncA, rpsA, and panD gene mutations.

Our study was aimed to identify the phenotypic and genotypic pyrazinamide (PZA) resistance features among multidrug-resistant (MDR) isolates in a national tuberculosis (TB) referral center of China. PZA susceptibility test was performed for a total of 142 MDR-TB clinical isolates using the MGIT 960 PZA kits, and the pncA, rpsA, and panD genes were sequenced. Extensively drug-resistant (XDR) and pre-XDR strains had higher PZA resistance rate than that of MDR strains which were still sensitive to fluoroquinolone and aminoglycoside (42.9%, 24/56) (χ(2)=8.922, P=0.012). No panD mutation was detected among the PZA resistant strains with wild-type pncA and rpsA genes. Our study indicates that PZA-resistant frequency increases with TB drug resistance level; pncA, rpsA, and panD mutations had strong, low, and no correlation with PZA resistance, and rapid molecular assay will facilitate the timely identification of the PZA-sensitive MDR-TB.

Antimicrobial susceptibility testing and genotyping of Mycobacterium avium isolates of two tertiary tuberculosis designated hospital, China.

BACKGROUND: Mycobacterium avium is frequently isolated from clinical samples, while the bacteriological features of M. avium clinical isolates from China have never been well defined. METHODS: A total of 50 M. avium isolates were recruited from two tertiary tuberculosis designated hospitals, one located in Beijing whereas another in Fujian Province, which are northern and southern parts of China, respectively. Subspecies identification was conducted by sequencing the variable 3' end of the hsp65 gene. The susceptibility against 15 antimicrobial agents, widely administered for the treatment of non-tuberculosis mycobacteria (NTM) infections, was tested by broth microdilution assay. Variable number of tandem repeats (VNTR) assay was also performed using the 16-loci genotyping method. RESULTS: All of the 50 M. avium isolates were identified as M. avium subsp. hominissuis. The drug susceptibility test revealed that clarithromycin (98%, 49/50) and moxifloxacin (86%, 43/50) had the best antimicrobial activities in vitro against the M. avium isolates. The overall Hunter-Gaston Discriminatory Index (HGDI) value for the VNTR typing was 0.95. However, the genotyping method yielded much greater discriminative power for isolates of northern China than that of southern China (1.00 V.S. 0.86, P<0.05). CONCLUSION: M. avium subsp. hominissuis is the dominate subspecies among M. avium clinical isolates in China. The 16-loci VNTR genotyping method is more discriminative in Beijing than in Fujian Province. The bacteriological features of M. avium isolates from different regions of China demonstrated dramatic variations, and stressed the importance of building up knowledge from the local isolates.