Newly synthesized surfactants for surface mannosylation of respirable SLN assemblies to target macrophages in tuberculosis therapy

The present study reports about new solid lipid nanoparticle assemblies (SLNas) loaded with rifampicin (RIF) surface-decorated with novel mannose derivatives, designed for anti-tuberculosis (TB) inhaled therapy by dry powder inhaler (DPI). Mannose is considered a relevant ligand to achieve active drug targeting being mannose receptors (MR) overexpressed on membranes of infected alveolar macrophages (AM), which are the preferred site of Mycobacterium tuberculosis. Surface decoration of SLNas was obtained by means of newly synthesized functionalizing compounds used as surfactants in the preparation of carriers. SLNas were fully characterized in vitro determining size, morphology, drug loading, drug release, surface mannosylation, cytotoxicity, macrophage internalization extent and ability to bind MR, and intracellular RIF concentration. Moreover, the influence of these new surface functionalizing agents on SLNas aerodynamic performance was assessed by measuring particle respirability features using next generation impactor. SLNas exhibited suitable drug payload, in vitro release, and more efficient ability to enter macrophages (about 80%) compared to bare RIF (about 20%) and to non-functionalized SLNas (about 40%). The involvement of MR-specific binding has been demonstrated by saturating MR of J774 cells causing a decrease of RIF intracellular concentration of about 40%. Furthermore, it is noteworthy that the surface decoration of particles produced a poor cohesive powder with an adequate respirability (fine particle fraction ranging from about 30 to 50%). Therefore, the proposed SLNas may represent an encouraging opportunity in a perspective of an efficacious anti-TB inhaled therapy.

Xpert MTB/RIF and Xpert MTB/RIF Ultra for pulmonary tuberculosis and rifampicin resistance in adults

BACKGROUND

Xpert MTB/RIF (Xpert MTB/RIF) and Xpert MTB/RIF Ultra (Xpert Ultra), the newest version, are the only World Health Organization (WHO)-recommended rapid tests that simultaneously detect tuberculosis and rifampicin resistance in persons with signs and symptoms of tuberculosis, at lower health system levels. A previous Cochrane Review found Xpert MTB/RIF sensitive and specific for tuberculosis (Steingart 2014). Since the previous review, new studies have been published. We performed a review update for an upcoming WHO policy review.

OBJECTIVES

To determine diagnostic accuracy of Xpert MTB/RIF and Xpert Ultra for tuberculosis in adults with presumptive pulmonary tuberculosis (PTB) and for rifampicin resistance in adults with presumptive rifampicin-resistant tuberculosis.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, Embase, Science Citation Index, Web of Science, Latin American Caribbean Health Sciences Literature, Scopus, the WHO International Clinical Trials Registry Platform, the International Standard Randomized Controlled Trial Number Registry, and ProQuest, to 11 October 2018, without language restriction.

SELECTION CRITERIA

Randomized trials, cross-sectional, and cohort studies using respiratory specimens that evaluated Xpert MTB/RIF, Xpert Ultra, or both against the reference standard, culture for tuberculosis and culture-based drug susceptibility testing or MTBDRplus for rifampicin resistance.

DATA COLLECTION AND ANALYSIS

Four review authors independently extracted data using a standardized form. When possible, we also extracted data by smear and HIV status. We assessed study quality using QUADAS-2 and performed meta-analyses to estimate pooled sensitivity and specificity separately for tuberculosis and rifampicin resistance. We investigated potential sources of heterogeneity. Most analyses used a bivariate random-effects model. For tuberculosis detection, we first estimated accuracy using all included studies and then only the subset of studies where participants were unselected, i.e. not selected based on prior microscopy testing.

MAIN RESULTS

We identified in total 95 studies (77 new studies since the previous review): 86 studies (42,091 participants) evaluated Xpert MTB/RIF for tuberculosis and 57 studies (8287 participants) for rifampicin resistance. One study compared Xpert MTB/RIF and Xpert Ultra on the same participant specimen.Tuberculosis detectionOf the total 86 studies, 45 took place in high tuberculosis burden and 50 in high TB/HIV burden countries. Most studies had low risk of bias.Xpert MTB/RIF pooled sensitivity and specificity (95% credible Interval (CrI)) were 85% (82% to 88%) and 98% (97% to 98%), (70 studies, 37,237 unselected participants; high-certainty evidence). We found similar accuracy when we included all studies.For a population of 1000 people where 100 have tuberculosis on culture, 103 would be Xpert MTB/RIF-positive and 18 (17%) would not have tuberculosis (false-positives); 897 would be Xpert MTB/RIF-negative and 15 (2%) would have tuberculosis (false-negatives).Xpert Ultra sensitivity (95% confidence interval (CI)) was 88% (85% to 91%) versus Xpert MTB/RIF 83% (79% to 86%); Xpert Ultra specificity was 96% (94% to 97%) versus Xpert MTB/RIF 98% (97% to 99%), (1 study, 1439 participants; moderate-certainty evidence).Xpert MTB/RIF pooled sensitivity was 98% (97% to 98%) in smear-positive and 67% (62% to 72%) in smear-negative, culture-positive participants, (45 studies). Xpert MTB/RIF pooled sensitivity was 88% (83% to 92%) in HIV-negative and 81% (75% to 86%) in HIV-positive participants; specificities were similar 98% (97% to 99%), (14 studies).Rifampicin resistance detectionXpert MTB/RIF pooled sensitivity and specificity (95% Crl) were 96% (94% to 97%) and 98% (98% to 99%), (48 studies, 8020 participants; high-certainty evidence).For a population of 1000 people where 100 have rifampicin-resistant tuberculosis, 114 would be positive for rifampicin-resistant tuberculosis and 18 (16%) would not have rifampicin resistance (false-positives); 886 would be would be negative for rifampicin-resistant tuberculosis and four (0.4%) would have rifampicin resistance (false-negatives).Xpert Ultra sensitivity (95% CI) was 95% (90% to 98%) versus Xpert MTB/RIF 95% (91% to 98%); Xpert Ultra specificity was 98% (97% to 99%) versus Xpert MTB/RIF 98% (96% to 99%), (1 study, 551 participants; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

We found Xpert MTB/RIF to be sensitive and specific for diagnosing PTB and rifampicin resistance, consistent with findings reported previously. Xpert MTB/RIF was more sensitive for tuberculosis in smear-positive than smear-negative participants and HIV-negative than HIV-positive participants. Compared with Xpert MTB/RIF, Xpert Ultra had higher sensitivity and lower specificity for tuberculosis and similar sensitivity and specificity for rifampicin resistance (1 study). Xpert MTB/RIF and Xpert Ultra provide accurate results and can allow rapid initiation of treatment for multidrug-resistant tuberculosis.

Early interaction between tacrolimus and rifampin

Drug interactions are unavoidable and need to be proactively identified and managed, in particular, the inductive effect of rifampin on tacrolimus whose potency and duration data are limited. We report the case of a renal transplant patient who was prescribed tacrolimus with preserved tough blood levels (C0) of 7.9 +/- 2 ng/mL. He presented ganglionic tuberculosis and started rifampin. One day later, C0 was 2.6 ng/mL with 5 mg/day. The serum creatinin was normal. Nine days later, C0 was 1.6 ng/mL with 7 mg/day. In this case-report, the tacrolimus-rifampin interaction occurred just one day after rifampin introduction necessitating early C0 monitoring.

An NAD+ Phosphorylase Toxin Triggers Mycobacterium tuberculosis Cell Death

Toxin-antitoxin (TA) systems regulate fundamental cellular processes in bacteria and represent potential therapeutic targets. We report a new RES-Xre TA system in multiple human pathogens, including Mycobacterium tuberculosis. The toxin, MbcT, is bactericidal unless neutralized by its antitoxin MbcA. To investigate the mechanism, we solved the 1.8 Å-resolution crystal structure of the MbcTA complex. We found that MbcT resembles secreted NAD+-dependent bacterial exotoxins, such as diphtheria toxin. Indeed, MbcT catalyzes NAD+ degradation in vitro and in vivo. Unexpectedly, the reaction is stimulated by inorganic phosphate, and our data reveal that MbcT is a NAD+ phosphorylase. In the absence of MbcA, MbcT triggers rapid M. tuberculosis cell death, which reduces mycobacterial survival in macrophages and prolongs the survival of infected mice. Our study expands the molecular activities employed by bacterial TA modules and uncovers a new class of enzymes that could be exploited to treat tuberculosis and other infectious diseases.

A Rapid Unraveling of the Activity and Antibiotic Susceptibility of Mycobacteria

The development of antibiotic-resistant bacteria is a worldwide health-related emergency that calls for new tools to study the bacterial metabolism and to obtain fast diagnoses. Indeed, the conventional analysis time scale is too long and affects our ability to fight infections. Slowly growing bacteria represent a bigger challenge, since their analysis may require up to months. Among these bacteria, Mycobacterium tuberculosis, the causative agent of tuberculosis, has caused more than 10 million new cases and 1.7 million deaths in 2016 only. We employed a particularly powerful nanomechanical oscillator, the nanomotion sensor, to characterize rapidly and in real time tuberculous and nontuberculous bacterial species, Mycobacterium bovis bacillus Calmette-Guérin and Mycobacterium abscessus, respectively, exposed to different antibiotics. Here, we show how high-speed and high-sensitivity detectors, the nanomotion sensors, can provide a rapid and reliable analysis of different mycobacterial species, obtaining qualitative and quantitative information on their responses to different drugs. This is the first application of the technique to tackle the urgent medical issue of mycobacterial infections, evaluating the dynamic response of bacteria to different antimicrobial families and the role of the replication rate in the resulting nanomotion pattern. In addition to a fast analysis, which could massively benefit patients and the overall health care system, we investigated the real-time responses of the bacteria to extract unique information on the bacterial mechanisms triggered in response to antibacterial pressure, with consequences both at the clinical level and at the microbiological level.

Discordant rifampicin susceptibility results are associated with Xpert® MTB/RIF probe B and probe binding delay

SETTING

Xpert® MTB/RIF is the first-line diagnostic test for Mycobacterium tuberculosis and rifampicin (RIF) resistance in South Africa.

OBJECTIVE

To describe the rates of Xpert RIF resistance not confirmed on follow-up testing, as well as the patient and test characteristics associated with discordant results.

DESIGN

Retrospective review of patients with isolates showing Xpert RIF resistance. Line-probe assay, phenotypic drug susceptibility testing or repeat Xpert were all considered confirmatory tests of RIF resistance. 'Discordance' was defined as a patient with RIF resistance identified on initial Xpert testing, with a subsequent confirmatory test indicating RIF susceptibility. Associations were analysed using Pearson χ² difference of proportions and modified Poisson regression.

RESULTS

RIF discordance occurred in 22/263 subjects and was associated with Xpert probe B, probe binding delay, as opposed to probe dropout, and probe binding delays (ΔCt) of between 4 and 4.9.

CONCLUSION

Discordant RIF resistance was common in our cohort and was associated with Xpert probe delay and use of probe B.

Impact of External Quality Assurance on the Quality of Xpert MTB/RIF Testing in Viet Nam

Following the endorsement of the Xpert MTB/RIF assay (Cepheid, Sunnyvale, CA, USA) by the World Health Organization (WHO) in 2010, Viet Nam's National Tuberculosis Control Program (NTP) began using GeneXpert instruments in NTP laboratories. In 2013, Viet Nam's NTP implemented an Xpert MTB/RIF external quality assurance (EQA) program in collaboration with the U.S. Centers for Disease Control and Prevention (CDC) and the Foundation for Innovative New Diagnostics (FIND). Proficiency-testing (PT) panels comprising five dried tube specimens (DTS) were sent to participating sites approximately twice a year from October 2013 to July 2016. The number of enrolled laboratories increased from 22 to 39 during the study period. Testing accuracy was assessed by comparing reported and expected results; percentage scores were assigned; and feedback reports were provided to sites. On-site evaluation (OSE) was conducted for underperforming laboratories. The results from the first five rounds demonstrate the positive impact of PT and targeted OSE visits on testing quality. On average, for every additional round of feedback, the odds of achieving PT scores of ≥80% increased 2.04-fold (95% confidence interval, 1.39- to 3.00-fold). Future work will include scaling up PT to all sites and maintaining the performance of participating laboratories while developing local panel production capacity.

Mycobacterium tuberculosis infection and resistance to rifampicin with GeneXpert®MTB/RIF: a single-center experience on bronchoalveolar lavage samples in renal failure patients

Patients with end-stage renal disease (ESRD) are immunocompromised and are more at risk to develop and acquire Mycobacterium tuberculosis (MTB) infection. However, risk assessment is uncertain. The objective of current research was to study the frequency of MTB infection in ESRD patients . For this purpose, bronchoalveolar lavage (BAL) samples were evaluated for the presence of MTB by using GeneXpert®MTB/RIF test. We analysed 350 clinical samples of BAL collected from a tertiary care hospital in Pakistan, from September, 2015 to July, 2016. We performed the GeneXpert®test on each sample. According to our results prevalence of MTB was observed in 1.7% of bronchoalveolar lavage (BAL) samples taken from patients with chronic kidney diseases. All the positive samples were susceptible to rifampicin. There is a low prevalence of MTB infec tion (pulmonar y tuberculosis) in patients with chronic kidney disease in our setup. Suspected patients can be diagnosed by using GeneXpert®MTB/RIF testing on bronchoalveolar lavage samples.

Role of CsrA in stress responses and metabolism important for Salmonella virulence revealed by integrated transcriptomics

To cause infection, Salmonella must survive and replicate in host niches that present dramatically different environmental conditions. This requires a flexible metabolism and physiology, responsive to conditions of the local milieu. The sequence specific RNA binding protein CsrA serves as a global regulator that governs gene expression required for pathogenicity, metabolism, biofilm formation, and motility in response to nutritional conditions. Its activity is determined by two noncoding small RNAs (sRNA), CsrB and CsrC, which sequester and antagonize this protein. Here, we used ribosome profiling and RNA-seq analysis to comprehensively examine the effects of CsrA on mRNA occupancy with ribosomes, a measure of translation, transcript stability, and the steady state levels of transcripts under in vitro SPI-1 inducing conditions, to simulate growth in the intestinal lumen, and under in vitro SPI-2-inducing conditions, to simulate growth in the Salmonella containing vacuole (SCV) of the macrophage. Our findings uncovered new roles for CsrA in controlling the expression of structural and regulatory genes involved in stress responses, metabolism, and virulence systems required for infection. We observed substantial variation in the CsrA regulon under the two growth conditions. In addition, CsrB/C sRNA levels were greatly reduced under the simulated intracellular conditions and were responsive to nutritional factors that distinguish the intracellular and luminal environments. Altogether, our results reveal CsrA to be a flexible regulator, which is inferred to be intimately involved in maintaining the distinct gene expression patterns associated with growth in the intestine and the macrophage.

Rifamycin congeners kanglemycins are active against rifampicin-resistant bacteria via a distinct mechanism

Rifamycin antibiotics (Rifs) target bacterial RNA polymerases (RNAPs) and are widely used to treat infections including tuberculosis. The utility of these compounds is threatened by the increasing incidence of resistance (RifR). As resistance mechanisms found in clinical settings may also occur in natural environments, here we postulated that bacteria could have evolved to produce rifamycin congeners active against clinically relevant resistance phenotypes. We survey soil metagenomes and identify a tailoring enzyme-rich family of gene clusters encoding biosynthesis of rifamycin congeners (kanglemycins, Kangs) with potent in vivo and in vitro activity against the most common clinically relevant RifR mutations. Our structural and mechanistic analyses reveal the basis for Kang inhibition of RifR RNAP. Unlike Rifs, Kangs function through a mechanism that includes interfering with 5'-initiating substrate binding. Our results suggest that examining soil microbiomes for new analogues of clinically used antibiotics may uncover metabolites capable of circumventing clinically important resistance mechanisms.

Meta-narrative review of molecular methods for diagnosis and monitoring of multidrug-resistant tuberculosis treatment in adults

Early and accurate diagnosis and rigorous clinical and microbiological monitoring of multidrug-resistant tuberculosis (MDR-TB) treatment can curb morbidity and mortality. While others are still under evaluation, the World Health Organization has recommended few novel molecular methods for MDR-TB diagnosis only. We present current molecular methods for diagnosis and monitoring of MDR-TB treatment in TB-endemic settings. A systematic meta-narrative review was conducted according to the RAMESES recommendations. Electronic databases were searched for relevant articles published in English language from January 2013 to June 2018. Based on predefined criteria, two independent reviewers extracted the key messages from relevant articles. Disagreement between them was resolved through discussion and the involvement of a third reviewer, if needed. Key messages were synthesized to create the meta-narratives for method's accuracy, drug-susceptibility capability, and laboratory infrastructure required. We included 33 articles out of 1213 records retrieved, of which 16 (48%) and 12 (36%) were conducted in high- and low-TB-endemic settings, respectively. Xpert® MTB/RIF, GenoType MTBDRplus, GenoType MTBDRsl, FlouroType™ MTBDR, TB TaqMan® array card, and DNA sequencers can accurately guide effective treatment regimens. Molecular bacterial load assay quantifies mycobactericidal impact of these regimens. Although they present inherent advantages compared to the current standard of care, they carry important limitations to implementation and/or scale-up. Therefore, considerable effort must now be directed to implementation and health systems research to maximize these forecasted benefits for individual patient's health outcomes.

Improvement of Mycobacterium tuberculosis detection by Xpert MTB/RIF Ultra: A head-to-head comparison on Xpert-negative samples

BACKGROUND

The new Xpert MTB/RIF Ultra assay (Ultra, Cepheid, Sunnyvale, USA) is a cartridge-based automated diagnostic test that can simultaneously identify Mycobacterium tuberculosis complex (MTB) and resistance to Rifampicin (RIF). With respect to the previous version Xpert MTB/RIF assay (Xpert), IS6110/IS1081 repetitive elements probes have been added allowing the detection of lower MTB load, defined by the new semi-quantitative category "trace" with indeterminate RIF resistance. The aim of this study was to evaluate performance of the new version Ultra on Xpert-negative, but TB culture-positive clinical samples.

METHODS

The de-identified frozen samples (-20 °C) collected over a 4-year period (February 2014-October 2017), which had previously resulted smear-negative, Xpert-negative but MTB culture-positive, were analyzed with Ultra. The de-frosted samples were loaded into the cartridge using the same process as the previous version, according to manufacturer's instruction.

RESULTS

During the study period 382 MTB culture-positive samples were archived: 314 resulted Xpert-positive and 68 Xpert-negative. Thirty-one of the 68 Xpert-negative samples resulted positive with Ultra, with an overall improvement in MTB detection of 45.6%. Out of 36 Xpert-negative respiratory samples, 18 resulted Ultra-positive with the following semi-quantitative loads: "low"(n = 1), "very low"(n = 11), "trace"(n = 6), with an improvement in MTB detection of 50%. The best performance was achieved on bronchoalveolar lavage specimens (53.8%). Out of 32 Xpert-negative non-respiratory samples, 13 resulted Ultra-positive with the following semi-quantitative loads: "very low"(n = 7), "trace"(n = 6), with an improvement in MTB detection of 40.6%. The best performance was achieved on biopsies (55.6%) and lymph nodes (50%). The new category "trace" detected 12 out of the 31 Ultra-positive MTB samples; in the remaining 19 samples RIF susceptibility was determined with 100% concordance with the phenotypic susceptibility test. The mean time to positivity of samples found negative by Ultra was significantly longer in comparison to positive samples in liquid culture.

CONCLUSIONS

Our results are consistent with the few studies published so far and confirm the better performance of Ultra compared to the previous version in both respiratory and non-respiratory smear-negative samples, with an overall improvement of 45.6%.

Diagnostic efficiency of Xpert MTB/RIF assay for osteoarticular tuberculosis in patients with inflammatory arthritis in China

BACKGROUND

Both osteoarticular tuberculosis (OA-TB) and inflammatory arthritis can lead to osteoarticular structural damage. These conditions exhibit similar symptoms, physical signs, and imaging features. Rapidly and accurately diagnosing OA-TB in patients with inflammatory arthritis presents a challenge to clinicians. Xpert MTB/RIF (Xpert) has been endorsed by the World Health Organization (WHO) as a rapid diagnostic tool for diagnosis of pulmonary and extrapulmonary TB. This study was designed to investigate diagnostic efficiency of Xpert for OA-TB in patients with inflammatory arthritis in China.

METHODS

A total of 83 consecutive patients with inflammatory arthritis and suspected OA-TB were enrolled prospectively from June 2014 to May 2018. Demographic, clinical, and biological data were recorded. Xpert assay, smear microscopy examination (smear), BACTEC MGIT 960 (MGIT 960), pathological examination, and T-SPOT.TB test were performed for each patient who received operations. Diagnostic efficiency of Xpert was evaluated based on a composite reference standard (CRS).

RESULTS

A total of 49 out of 83 patients with inflammatory arthritis and suspected OA-TB received operations, and 49 specimens were obtained during operations. According to CRS, 36 out of 49 patients with inflammatory arthritis were diagnosed with OA-TB, and 13 were not affected by the condition. Sensitivity of Xpert assay, smear, MGIT 960, pathological examination, and T-SPOT.TB test reached 66.70% (24/36), 25.00% (9/36), 30.55% (11/36), 47.22% (17/36), and 80.55% (29/36), respectively. Specificity of Xpert assay, smear, MGIT 960, and pathological examination was all 100% (13/13). Specificity of T-SPOT.TB test was 53.84% (7/13). Sensitivity of Xpert was higher than that of smear, MGIT 960 and pathological examination, but the sensitivity of Xpert was lower than that of T-SPOT.TB. Sensitivity of Xpert was statistically different from that of smear and MGIT 960 (P<0.001, P = 0.002), but the sensitivity of Xpert was not significantly different from that of pathological examination and T-SPOT.TB (P = 0.096, P = 0.181). Specificity of T-SPOT.TB was less than that of Xpert, smear, MGIT 960, and pathological examination, and the difference between them was statistically significant (P = 0.015). Among the 27 OA-TB patients with smear negative results, Xpert had the highest sensitivity, but sensitivity of Xpert was not significantly different from that of pathological examination and T-SPOT.TB (P = 0.413, P = 0.783). 2 of 36 OA-TB patients exhibited RIF resistance. Xpert was concordant with MGIT 960-based drug susceptibility testing (DST) in detecting rifampin (RIF) resistance.

CONCLUSIONS

Xpert is an efficient tool with high sensitivity and specificity for OA-TB diagnosis in patients with inflammatory arthritis in high-TB prevalence countries. Compared with conventional methods, Xpert has two advantages: one is fast, and the other is able to provide RIF resistance information simultaneously.

Precise Cas9 targeting enables genomic mutation prevention

Here, we present a generalized method of guide RNA "tuning" that enables Cas9 to discriminate between two target sites that differ by a single-nucleotide polymorphism. We employ our methodology to generate an in vivo mutation prevention system in which Cas9 actively restricts the occurrence of undesired gain-of-function mutations within a population of engineered organisms. We further demonstrate that the system is scalable to a multitude of targets and that the general tuning and prevention concepts are portable across engineered Cas9 variants and Cas9 orthologs. Finally, we show that the mutation prevention system maintains robust activity even when placed within the complex environment of the mouse gastrointestinal tract.

Comparison of the yield of tuberculosis among contacts of multidrug-resistant and drug-sensitive tuberculosis patients in Ethiopia using GeneXpert as a primary diagnostic test

OBJECTIVES

This study compared the yield of tuberculosis (TB) among contacts of multidrug-resistant tuberculosis (MDR-TB) index cases with that in drug-sensitive TB (DS-TB) index cases in a program setting.

METHODS

A comparative cross-sectional study was conducted among contacts of sputum smear-positive new DS-TB index cases and MDR-TB index cases. After contacts were screened, GeneXpert was used for the diagnosis of TB.

RESULTS

The study included 111 MDR-TB and 119 DS-TB index cases. A total of 340 and 393 contacts of MDR-TB and DS-TB index cases, respectively, were traced, of whom 331 among MDR-TB contacts and 353 among DS-TB contacts were screened. There were 20 (6%) presumptive TB cases for MDR-TB contacts and 41 (11%) for DS-TB contacts. The prevalence of TB among MDR-TB contacts was 2.7% and among DS-TB contacts was 4.0%. The majority of the MDR-TB contacts diagnosed with TB had MDR-TB; the reverse was true for DS-TB.

CONCLUSIONS

The yield of TB among contacts of MDR-TB and DS-TB patients using GeneXpert was high as compared to the population-level prevalence. The likelihood of diagnosing rifampicin-resistant TB among contacts of MDR-TB index cases was higher in comparison with contacts of DS-TB index cases. The use of GeneXpert in DS-TB contact investigation has the added advantage of diagnosing rifampicin-resistant TB cases when compared to the use of the nationally recommended acid-fast bacillus (AFB) microscopy for DS-TB contact investigation.

Adjunctive rifampicin for Staphylococcus aureus bacteraemia (ARREST): a multicentre, randomised, double-blind, placebo-controlled trial

BACKGROUND

Staphylococcus aureus bacteraemia is a common cause of severe community-acquired and hospital-acquired infection worldwide. We tested the hypothesis that adjunctive rifampicin would reduce bacteriologically confirmed treatment failure or disease recurrence, or death, by enhancing early S aureus killing, sterilising infected foci and blood faster, and reducing risks of dissemination and metastatic infection.

METHODS

In this multicentre, randomised, double-blind, placebo-controlled trial, adults (≥18 years) with S aureus bacteraemia who had received ≤96 h of active antibiotic therapy were recruited from 29 UK hospitals. Patients were randomly assigned (1:1) via a computer-generated sequential randomisation list to receive 2 weeks of adjunctive rifampicin (600 mg or 900 mg per day according to weight, oral or intravenous) versus identical placebo, together with standard antibiotic therapy. Randomisation was stratified by centre. Patients, investigators, and those caring for the patients were masked to group allocation. The primary outcome was time to bacteriologically confirmed treatment failure or disease recurrence, or death (all-cause), from randomisation to 12 weeks, adjudicated by an independent review committee masked to the treatment. Analysis was intention to treat. This trial was registered, number ISRCTN37666216, and is closed to new participants.

FINDINGS

Between Dec 10, 2012, and Oct 25, 2016, 758 eligible participants were randomly assigned: 370 to rifampicin and 388 to placebo. 485 (64%) participants had community-acquired S aureus infections, and 132 (17%) had nosocomial S aureus infections. 47 (6%) had meticillin-resistant infections. 301 (40%) participants had an initial deep infection focus. Standard antibiotics were given for 29 (IQR 18-45) days; 619 (82%) participants received flucloxacillin. By week 12, 62 (17%) of participants who received rifampicin versus 71 (18%) who received placebo experienced treatment failure or disease recurrence, or died (absolute risk difference -1·4%, 95% CI -7·0 to 4·3; hazard ratio 0·96, 0·68-1·35, p=0·81). From randomisation to 12 weeks, no evidence of differences in serious (p=0·17) or grade 3-4 (p=0·36) adverse events were observed; however, 63 (17%) participants in the rifampicin group versus 39 (10%) in the placebo group had antibiotic or trial drug-modifying adverse events (p=0·004), and 24 (6%) versus six (2%) had drug interactions (p=0·0005).

INTERPRETATION

Adjunctive rifampicin provided no overall benefit over standard antibiotic therapy in adults with S aureus bacteraemia.

FUNDING

UK National Institute for Health Research Health Technology Assessment.

Xpert MTB/RIF Ultra for detection of Mycobacterium tuberculosis and rifampicin resistance: a prospective multicentre diagnostic accuracy study

BACKGROUND

The Xpert MTB/RIF assay is an automated molecular test that has improved the detection of tuberculosis and rifampicin resistance, but its sensitivity is inadequate in patients with paucibacillary disease or HIV. Xpert MTB/RIF Ultra (Xpert Ultra) was developed to overcome this limitation. We compared the diagnostic performance of Xpert Ultra with that of Xpert for detection of tuberculosis and rifampicin resistance.

METHODS

In this prospective, multicentre, diagnostic accuracy study, we recruited adults with pulmonary tuberculosis symptoms presenting at primary health-care centres and hospitals in eight countries (South Africa, Uganda, Kenya, India, China, Georgia, Belarus, and Brazil). Participants were allocated to the case detection group if no drugs had been taken for tuberculosis in the past 6 months or to the multidrug-resistance risk group if drugs for tuberculosis had been taken in the past 6 months, but drug resistance was suspected. Demographic information, medical history, chest imaging results, and HIV test results were recorded at enrolment, and each participant gave at least three sputum specimen on 2 separate days. Xpert and Xpert Ultra diagnostic performance in the same sputum specimen was compared with culture tests and drug susceptibility testing as reference standards. The primary objectives were to estimate and compare the sensitivity of Xpert Ultra test with that of Xpert for detection of smear-negative tuberculosis and rifampicin resistance and to estimate and compare Xpert Ultra and Xpert specificities for detection of rifampicin resistance. Study participants in the case detection group were included in all analyses, whereas participants in the multidrug-resistance risk group were only included in analyses of rifampicin-resistance detection.

FINDINGS

Between Feb 18, and Dec 24, 2016, we enrolled 2368 participants for sputum sampling. 248 participants were excluded from the analysis, and 1753 participants were distributed to the case detection group (n=1439) and the multidrug-resistance risk group (n=314). Sensitivities of Xpert Ultra and Xpert were 63% and 46%, respectively, for the 137 participants with smear-negative and culture-positive sputum (difference of 17%, 95% CI 10 to 24); 90% and 77%, respectively, for the 115 HIV-positive participants with culture-positive sputum (13%, 6·4 to 21); and 88% and 83%, respectively, across all 462 participants with culture-positive sputum (5·4%, 3·3 to 8·0). Specificities of Xpert Ultra and Xpert for case detection were 96% and 98% (-2·7%, -3·9 to -1·7) overall, and 93% and 98% for patients with a history of tuberculosis. Xpert Ultra and Xpert performed similarly in detecting rifampicin resistance.

INTERPRETATION

For tuberculosis case detection, sensitivity of Xpert Ultra was superior to that of Xpert in patients with paucibacillary disease and in patients with HIV. However, this increase in sensitivity came at the expense of a decrease in specificity.

FUNDING

Government of Netherlands, Government of Australia, Bill & Melinda Gates Foundation, Government of the UK, and the National Institute of Allergy and Infectious Diseases.

Role of Alanine Racemase Mutations in Mycobacterium tuberculosis d-Cycloserine Resistance

A screening of more than 1,500 drug-resistant strains of Mycobacterium tuberculosis revealed evolutionary patterns characteristic of positive selection for three alanine racemase (Alr) mutations. We investigated these mutations using molecular modeling, in vitro MIC testing, as well as direct measurements of enzymatic activity, which demonstrated that these mutations likely confer resistance to d-cycloserine.

Rifampicin-induced injury in HepG2 cells is alleviated by TUDCA via increasing bile acid transporters expression and enhancing the Nrf2-mediated adaptive response

Bile acid transporters and the nuclear factor erythroid 2-related factor (Nrf-2)-mediated adaptive response play important roles in the development of drug-induced liver injury (DILI). However, little is known about the contribution of the adaptive response to rifampicin (RFP)-induced cell injury. In this study, we found RFP decreased the survival rate of HepG2 cells and increased the levels of lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), γ-glutamyl-transferase (γ-GT), total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL), total bile acid (TBA) and adenosine triphosphate (ATP) in the cell culture supernatants in both a concentration- and a time-dependent manner. RFP increased the expression levels of bile acid transporter proteins and mRNAs, such as bile salt export pump (BSEP), multidrug resistance protein 1 (MDR1), multidrug resistance-associated protein 2 (MRP2), Na+/taurocholate cotransporter (NTCP), organic anion transporting protein 2 (OATP2), organic solute transporter β (OSTβ) and Nrf2. Following the transient knockdown of Nrf2 and treatment with RFP, the expression levels of the BSEP, MDR1, MRP2, NTCP, OATP2 and OSTβ proteins and mRNAs were decreased to different degrees. Moreover, the cell survival was decreased, whereas the LDH level in the cell culture supernatant was increased. Overexpression of the Nrf2 gene produced the opposite effects. Treatment with tauroursodeoxycholic acid (TUDCA) increased the expression levels of the bile acid transporters and Nrf2, decreased the expression levels of glucose-regulated protein 78 (GRP78), PKR-like ER kinase (PERK), activating transcription factor 4 (ATF4), and C/EBP-homologous protein (CHOP), and inhibited RFP-induced oxidative stress. Moreover, TUDCA reduced cell apoptosis, increased cell survival and decreased the levels of LDH, ALT, AST, AKP, γ-GT, TBIL, DBIL, IBIL, TBA and ATP in the cell culture supernatant. Therefore, TUDCA alleviates RFP-induced injury in HepG2 cells by enhancing bile acid transporters expression and the Nrf2-mediated adaptive response.

Comparative yielding of BACTEC MGIT 960 and GeneXpert MTB/RIF Assay for Rapid Diagnosis of Drug Resistance Tuberculosis from Sputum Specimen

Among communicable disease, tuberculosis is the second leading cause of death worldwide, killing nearly two million people each year. Several diagnostic techniques are currently used to detect mycobacteria in respiratory specimens. Therefore an alternative, rapid and most effective method is required for diagnosis of pulmonary tuberculosis which is relatively more sensitive and specific. A total of 107 sputum samples of suspected TB patients were enrolled attending the National Tuberculosis Reference Laboratory (NTRL), Mohakhali, Dhaka, Bangladesh from July 2014 to July 2015. Liquid culture of 107 sputum samples, yielded 76.63% culture positive and 1.86% contamination was observed. Antibiotic susceptibility test was done for 82 culture positive sputum samples among which 28.04% cases were resistant to both Rifampicin and Isoniazid. GeneXpert assay detected 85.04% M. tuberculosis among which 25.23% were found to be Rifampicin Resistance.

Treatment initiation among persons diagnosed with drug resistant tuberculosis in Johannesburg, South Africa

BACKGROUND

In South Africa, roughly half of the drug-resistant TB cases diagnosed are reported to have been started on treatment. We determined the proportion of persons diagnosed with rifampicin resistant (RR-) TB who initiated treatment in Johannesburg after the introduction of decentralized RR-TB care in 2011.

METHODS

We retrospectively matched adult patients diagnosed with laboratory-confirmed RR-TB in Johannesburg from 07/2011-06/2012 with records of patients initiating RR-TB treatment at one of the city's four public sector treatment sites (one centralized, three decentralized). Patients were followed from date of diagnosis until the earliest of RR-TB treatment initiation, death, or 6 months' follow-up. We report diagnostic methods and outcomes, proportions initiating treatment, and median time from diagnosis to treatment initiation.

RESULTS

594 patients were enrolled (median age 34 (IQR 29-42), 287 (48.3%) female). Diagnosis was by GenoType MTBDRplus (Hain-Life-Science) line probe assay (LPA) (281, 47.3%), Xpert MTB/RIF (Cepheid) (258, 43.4%), or phenotypic drug susceptibility testing (DST) (30, 5.1%) with 25 (4.2%) missing a diagnosis method. 320 patients (53.8%) had multi-drug resistant TB, 158 (26.6%) rifampicin resistant TB by Xpert MTB/RIF, 102 (17.2%) rifampicin mono-resistance, and 14 (2.4%) extensively drug-resistant TB. 256/594 (43.0%) patients initiated treatment, representing 70.7% of those who were referred for treatment (362/594). 338/594 patients (57.0%) did not initiate treatment, including 104 (17.5%) who died before treatment was started. The median time from sputum collection to treatment initiation was 33 days (IQR 12-52).

CONCLUSION

Despite decentralized RR-TB treatment, fewer than half the patients diagnosed in Johannesburg initiated appropriate treatment. Offering treatment at decentralized sites alone is not sufficient; improvements in linking patients diagnosed with RR-TB to effective treatment is essential.

Detection of Mycobacterium tuberculosis from paraffin-embedded tissues by GeneXpert MTB/RIF

GeneXpert MTB/RIF (Xpert) assay, a rapid and automated system based on real-time PCR and molecular beacon technology, proved to be a sensitive and specific tool capable of detecting Mycobacterium tuberculosis and rifampin resistance in clinical specimens. In this study we provide a Xpert-dedicated successful protocol for processing paraffin-embedded tissue and assess the feasibility of the Xpert assay-based tuberculosis (TB) diagnosis on these specimens, thus proving the Xpert assay as a valuable TB diagnostic tool in supporting conventional histopathological methods.

Clinical and in vitro efficacy of colistin plus vancomycin and rifampin against colistin-resistant Acinetobacter baumannii causing ventilator-associated pneumonia

We present the case of a patient with ventilator-associated pneumonia (VAP) caused by a pan-resistant Acinetobacter baumannii successfully treated with the combination colistin plus vancomycin plus rifampin, whose in vitro activity was investigated by checkerboard method and killing testing. Furthermore, the serum bactericidal activity (SBA) was assessed. Our case shows that an innovative regimen consisting of colistin plus antimicrobials active only against Gram-positive microorganisms might represent a valid therapeutic option for severe infections caused by colistin-resistant A. baumannii.