Background Improved monitoring of Mycobacterium tuberculosis response to treatment is urgently required. We previously developed the molecular bacterial load assay (MBLA), but it is challenging to integrate into the clinical diagnostic laboratory due to a labor-intensive protocol required at biosafety level 3 (BSL-3). A modified assay was needed.Methods The rapid enumeration and diagnostic for tuberculosis (READ-TB) assay was developed. Acetic acid was tested and compared to 4 M guanidine thiocyanate to be simultaneously bactericidal and preserve mycobacterial RNA. The extraction was based on silica column technology and incorporated low-cost reagents: 3 M sodium acetate and ethanol for the RNA extraction to replace phenol-chloroform. READ-TB was fully validated and compared directly to the MBLA using sputa collected from individuals with tuberculosis.Results Acetic acid was bactericidal to M. tuberculosis with no significant loss in 16S rRNA or an unprotected mRNA fragment when sputum was stored in acetic acid at 25 degrees C for 2 weeks or -20 degrees C for 1 year. This novel use of acetic acid allows processing of sputum for READ-TB at biosafety level 2 (BSL-2) on sample receipt. READ-TB is semiautomated and rapid. READ-TB correlated with the MBLA when 85 human sputum samples were directly compared (R2 = 0.74).Conclusions READ-TB is an improved version of the MBLA and is available to be adopted by clinical microbiology laboratories as a tool for tuberculosis treatment monitoring. READ-TB will have a particular impact in low- and middle-income countries (LMICs) for laboratories with no BSL-3 laboratory and for clinical trials testing new combinations of anti-tuberculosis drugs.

Background Drug resistance in tuberculosis (TB) poses a major ongoing challenge to public health. The recent inclusion of bedaquiline into TB drug regimens has improved treatment outcomes, but this advance is threatened by the emergence of strains of Mycobacterium tuberculosis ( Mtb ) resistant to bedaquiline. Clinical bedaquiline resistance is most frequently conferred by off-target resistance-associated variants (RAVs) in the mmpR5 gene ( Rv0678 ), the regulator of an efflux pump, which can also confer cross-resistance to clofazimine, another TB drug. Methods We compiled a dataset of 3682 Mtb genomes, including 180 carrying variants in mmpR5 , and its immediate background (i.e. mmpR5 promoter and adjacent mmpL5 gene), that have been associated to borderline (henceforth intermediate) or confirmed resistance to bedaquiline. We characterised the occurrence of all nonsynonymous mutations in mmpR5 in this dataset and estimated, using time-resolved phylogenetic methods, the age of their emergence. Results We identified eight cases where RAVs were present in the genomes of strains collected prior to the use of bedaquiline in TB treatment regimes. Phylogenetic reconstruction points to multiple emergence events and circulation of RAVs in mmpR5 , some estimated to predate the introduction of bedaquiline. However, epistatic interactions can complicate bedaquiline drug-susceptibility prediction from genetic sequence data. Indeed, in one clade, Ile67fs (a RAV when considered in isolation) was estimated to have emerged prior to the antibiotic era, together with a resistance reverting mmpL5 mutation. Conclusions The presence of a pre-existing reservoir of Mtb strains carrying bedaquiline RAVs prior to its clinical use augments the need for rapid drug susceptibility testing and individualised regimen selection to safeguard the use of bedaquiline in TB care and control.

New classes of antitubercular drugs, diarylquinolines and nitroimidazoles, have been associated with improved outcomes in the treatment of drug-resistant tuberculosis, but that success is threatened by emerging drug resistance. We report a case of bedaquiline and delamanid resistance in a 55-year-old woman in South Africa with extensively drug-resistant tuberculosis and known HIV.

Mycobacterium tuberculosis has acquired drug resistance to all drugs that have been used against it, including those only recently introduced into clinical practice. Compared to other bacteria, it has a well conserved genome due to its role as an obligate human pathogen that has adapted to a niche over five to ten thousand years. These features facilitate reconstruction and dating of M. tuberculosis phylogenies, giving key insights into how resistance has been acquired and spread globally. Resistance to each new drug has occurred within five to ten years of clinical use and has occurred even more rapidly with recently introduced drugs. In most cases, resistance-conferring mutations come with a fitness cost, but this can be overcome by compensatory mutations which restore fitness to that of wild-type bacteria. It is likely that M. tuberculosis acquires drug resistance while maintaining limited genomic variability due the generation of low frequency within-host variation, combined with ongoing purifying selection causing loss of variants without a clear fitness advantage. However, variants that do confer an advantage, such as drug resistance, can increase in prevalence amongst all bacteria within a host and become the dominant clone. These resistant strains can then be transmitted leading to primary drug resistant infection in a new host. As many countries move towards genomic methods for diagnosis of M. tuberculosis infection and drug resistance, it is important to be aware of the implications for the evolution of resistance. Currently, understanding of resistance-conferring mutations is incomplete, and some targeted genetic diagnostics create their own selective pressures. We discuss an example where a rifampicin resistance-conferring mutation which was not routinely covered by standard testing became dominant. Finally, resistance to new drugs such as bedaquiline and delamanid is caused by individually rare mutations occurring across a large mutational genomic target that have been detected over a short time, and do not provide statistical power for genotype-phenotype correlation - in contrast to longer-established drugs that form the backbone of drug-sensitive antituberculosis therapy. Therefore, we need a different approach to identify resistance-conferring mutations of new drugs before their resistance becomes widespread, abrogating their usefulness.

The Comprehensive Resistance Prediction for Tuberculosis: an International Consortium (CRyPTIC) presents here a data compendium of 12,289 Mycobacterium tuberculosis global clinical isolates, all of which have undergone whole-genome sequencing and have had their minimum inhibitory concentrations to 13 antitubercular drugs measured in a single assay. It is the largest matched phenotypic and genotypic dataset for M. tuberculosis to date. Here, we provide a summary detailing the breadth of data collected, along with a description of how the isolates were selected, collected, and uniformly processed in CRyPTIC partner laboratories across 23 countries. The compendium contains 6,814 isolates resistant to at least 1 drug, including 2,129 samples that fully satisfy the clinical definitions of rifampicin resistant (RR), multidrug resistant (MDR), pre-extensively drug resistant (pre-XDR), or extensively drug resistant (XDR). The data are enriched for rare resistance-associated variants, and the current limits of genotypic prediction of resistance status (sensitive/resistant) are presented by using a genetic mutation catalogue, along with the presence of suspected resistance-conferring mutations for isolates resistant to the newly introduced drugs bedaquiline, clofazimine, delamanid, and linezolid. Finally, a case study of rifampicin monoresistance demonstrates how this compendium could be used to advance our genetic understanding of rare resistance phenotypes. The data compendium is fully open source and it is hoped that it will facilitate and inspire future research for years to come.

Background Bedaquiline has become a key drug for treatment of drug-resistant tuberculosis. Most clinical resistance is conferred by mutations in Rv0678, a negative repressor of the MmpL5 efflux pump, and confer clofazimine cross-resistance. Here, we estimate the date of emergence of several Rv0678 variants in global Mycobacterium tuberculosis lineages. Methods We constructed global whole genome sequence datasets of thousands of lineage 2 and 4 isolates using newly generated and publicly available data. We enriched these by screening public repositories for sequences containing all previously reported Rv0678 variants. We built a whole genome maximum likelihood phylogenetic tree using RAxML-Ng and dated the nodes of this phylogeny using BEAST. The lineage 2 dataset contained 1514 sequences from isolates collected between 1994–2019. The lineage 4 dataset contained 2168 sequences including three from 18th century mummies. Results We identified 483 non-synonymous and promoter variants in 439 sequences. 25 sequences were from isolates collected prior to bedaquiline clinical trials in 2007 and 21 of these contained bedaquiline resistance-associated variants. Most Rv0678 mutations occurred in sequences carrying other resistance variants. In lineage 2 we identify 58 unique emergences of resistance estimated to have occurred between 1988–2018 (figure 1), of which 40 were represented by a single genome. In lineage 4 we identify 85 unique emergences estimated to have occurred between 1701–2019 (figure 1), of which 59 were represented by a single genome. We also identified a clade of 65 samples carrying the Ile67fs variant that we estimated to have arisen in 1701 (1657–1732). This predates the first use of clofazimine or bedaquiline. Conclusions Rv0678 mutations conferring bedaquiline/clofazimine resistance have been in circulation since before the antibiotic era, implying non-synonymous mutations in Rv0678 have little fitness cost. This pre-existing reservoir of resistant strains is likely to expand with increasing bedaquiline and clofazimine use.

Background. Bedaquiline has a black-box warning of the risk of arrhythmias and sudden death. This study aimed to determine the incidence of QTc prolongation and cardiac events in patients receiving bedaquiline for drug-resistant tuberculosis (DR-TB) under programmatic conditions. Methods. Retrospective cohort study of patients receiving bedaquiline at a DR-TB hospital in KwaZulu Natal, South Africa from September 2017 to February 2019. The primary outcome, a prolonged QT interval corrected using the Fridericia formula (QTcF), was defined as QTcF >500 ms, QTcF change >60 ms from baseline, or both. Results. Among 420 patients (66.2% male, median age 36 years), the median QTcF was 406.4 (interquartile range [IQR], 389.1-421.3) ms at baseline, increasing to 430.5 (IQR, 414.4-445.1) ms by 3 months and 434.0 (IQR, 419.0-447.9) ms at 6 months. Eighteen of 420 patients (4.3%) had a QTcF >500 ms and 110 of 420 patients (26.2%) had a QTcF change >60 ms. There were no recorded arrhythmias or cardiac deaths. Odds of prolonged QTcF were increased with concomitant azoles (adjusted odds ratio [aOR], 5.61 [95% confidence interval (CI), 2.26-13.91]; P < .001) and an inverse association with HIV-positive status (aOR, 0.34 [95% CI, .15-.75]; P = .008) and hypertension (aOR, 0.13 [95% CI, .02-.86]; P = .02). After prolongation, the QTcF declined to <500 ms, whether drugs were interrupted or not. Conclusions. We observed a modest prolongation of QTcF, maximal at week 15; there were no recorded arrhythmias or related deaths.

BackgroundBedaquiline and clofazimine are important drugs in the treatment of drug-resistant tuberculosis and are commonly used across southern Africa, although drug susceptibility testing is not routinely performed. In this study, we did a genotypic and phenotypic analysis of drug-resistant Mycobacterium tuberculosis isolates from cohort studies in hospitals in KwaZulu-Natal, South Africa, to identify resistance-associated variants (RAVs) and assess the extent of clofazimine and bedaquiline cross-resistance. We also used a comprehensive dataset of whole-genome sequences to investigate the phylogenetic and geographical distribution of bedaquiline and clofazimine RAVs in southern Africa.MethodsIn this study, we included M tuberculosis isolates reported from the PRAXIS study of patients with drug-resistant tuberculosis treated with bedaquiline (King Dinuzulu Hospital, Durban) and three other cohort studies of drug-resistant tuberculosis in other KwaZulu-Natal hospitals, and sequential isolates from six persistently culture-positive patients with extensively drug-resistant tuberculosis at the KwaZulu-Natal provincial referral laboratory. Samples were collected between 2013 and 2019. Microbiological cultures were done as part of all parent studies. We sequenced whole genomes of included isolates and measured bedaquiline and clofazimine minimum inhibitory concentrations (MICs) for isolates identified as carrying any Rv0678 variant or previously published atpE, pepQ, and Rv1979c RAVs, which were the subject of the phenotypic study. We combined all whole-genome sequences of M tuberculosis obtained in this study with publicly available sequence data from other tuberculosis studies in southern Africa (defined as the countries of the Southern African Development Community), including isolates with Rv0678 variants identified by screening public genomic databases. We used this extended dataset to reconstruct phylogenetic relationships across lineage 2 and 4 M tuberculosis isolates.FindingsWe sequenced the whole genome of 648 isolates from 385 patients with drug-resistant tuberculosis recruited into cohort studies in KwaZulu-Natal, and 28 isolates from six patients from the KwaZulu-Natal referral laboratory. We identified 30 isolates with Rv0678 RAVs from 16 (4%) of 391 patients. We did not identify any atpE, pepQ, or Rv1979c RAVs. MICs were measured for 21 isolates with Rv0678 RAVs. MICs were above the critical concentration for bedaquiline resistance in nine (43%) of 21 isolates, in the intermediate category in nine (43%) isolates, and within the wild-type range in three (14%) isolates. Clofazimine MICs in genetically wild-type isolates ranged from 0·12–0·5 μg/mL, and in isolates with RAVs from 0·25–4·0 μg/mL. Phylogenetic analysis of the extended dataset including M tuberculosis isolates from southern Africa resolved multiple emergences of Rv0678 variants in lineages 2 and 4, documented two likely nosocomial transmission events, and identified the spread of a possibly bedaquiline and clofazimine cross-resistant clone in eSwatini. We also identified four patients with pepQ frameshift mutations that may confer resistance.InterpretationBedaquiline and clofazimine cross-resistance in southern Africa is emerging repeatedly, with evidence of onward transmission largely due to Rv0678 mutations in M tuberculosis. Roll-out of bedaquiline and clofazimine treatment in the setting of limited drug susceptibility testing could allow further spread of resistance. Designing strong regimens would help reduce the emergence of resistance. Drug susceptibility testing is required to identify where resistance does emerge.FundingWellcome Trust, National Institute of Allergy and Infectious Diseases and National Center for Advancing Translational Sciences of the National Institutes of Health.

Background Distribution of N-acetyltransferase2 ( NAT2 ) polymorphisms varies considerably among different ethnic groups. Information on NAT2 single-nucleotide polymorphisms in South African population is limited. We investigated NAT2 polymorphisms and their effect on isoniazid pharmacokinetics in Zulu black HIV-infected South Africans in Durban, South Africa. Methods: HIV-infected participants with culture-confirmed pulmonary tuberculosis (TB) were enrolled from two unrelated studies. Culture-confirmed participants were genotyped for NAT2 polymorphisms 282C>T, 341T>C, 481C>T, 857G>A, 590G>A and 803A>G using Life Technologies pre-validated Taqman assays (Life Technologies, Paisley, UK). Participants underwent sampling for determination of plasma isoniazid and N -acetylisoniazid concentrations. Results Amongst the 120 patients, 63/120 (52.5%) were slow metabolisers ( NAT2 *5/*5), 43/120 (35.8%) had intermediate ( NAT2*5/12 ), and 12/120 (11.7%) had rapid genotype ( NAT2*4/*11, NAT2*11/12 and NAT2*12/12 ). NAT2 alleles in this study were *4, *5C, *5D, *5E, *5J, *5K, *5KA, *5T, *11A, *12A/12C and *12M. NAT2*5 was the most frequent allele (70.4%) followed by NAT2 *12 (27.9%). 34/40 had both PK results and NAT2 genotyping results. The median area under the concentration-time-curve to infinity (AUC 0-∞ ) interquartile range (IQR) was 7.81 (5.87 – 16.83) μg/ml/hr and maximum concentration (Cmax) 3.14 μg/ml (2.42 – 4.36) μg/mL. Individual polymorphisms were not equally distributed, with some represented in small numbers. Genotype did not correlate with phenotype, rapid genotype showing higher AUC 0-∞ than slow but not significant, p=0.43. Conclusion There was high prevalence of slow followed by intermediate then rapid acetylator genotypes. The poor concordance between genotype and phenotype suggests that other factors or genetic loci influence INH metabolism, and warrants further investigation in this population.

AbstractBackgroundStudying within-host genetic diversity ofMycobacterium tuberculosis(Mtb) in patients during treatment may identify adaptations to antibiotic and immune pressure. Understanding the significance of genetic heteroresistance, and more specifically heterozygous resistance-associated variants (RAVs), is clinically important given increasing use of rapid molecular tests and whole genome sequencing (WGS).MethodsWe analyse data from six studies in KwaZulu-Natal, South Africa. Most patients (>75%) had baseline rifampicin-resistance. Sputum was collected for culture at baseline and at between two and nine intervals until month six. Positive cultures underwent WGS. Mixed infections and reinfections were excluded from analysis.FindingsBaselineMtboverall genetic diversity (at treatment initiation or major change to regimen) was associated with cavitary disease, not taking antiretroviral therapy if HIV infected, infection with lineage 2 strains and absence of second-line drug resistance on univariate analyses. Baseline genetic diversity was not associated with six-month outcome. Genetic diversity increased from baseline to weeks one and two before returning to previous levels. Baseline genetic heteroresistance was most common for bedaquiline (6/10 [60%] of isolates with RAVs) and fluoroquinolones (9/62 [13%]). Most patients with heterozygous RAVs on WGS with sequential isolates available demonstrated persistence or fixation (17/20, 85%). New RAVs emerged in 9/286 (3%) patients during treatment. We could detect low-frequency RAVs preceding emergent resistance in only one case, although validation of deep sequencing to detect rare variants is required.InterpretationIn this study of single-strainMtbinfections, baseline within-host bacterial genetic diversity did not predict outcome but may reveal adaptations to host and drug pressures. Predicting emergent resistance from low-frequency RAVs requires further work to separate transient from consequential mutations.FundingWellcome Trust, NIH/NIAID

Genetic mutations linked to bedaquiline resistance were found before starting treatment and acquired during treatment in patients with drug-resistant TB and HIV in KwaZulu-Natal, South Africa. Routine bedaquiline resistance testing needs to be accelerated.http://bit.ly/2vnL4VY

BACKGROUND:Studying within-host genetic diversity of Mycobacterium tuberculosis (Mtb) in patients during treatment may identify adaptations to antibiotic and immune pressure. Understanding the significance of genetic heteroresistance, and more specifically heterozygous resistance-associated variants (RAVs), is clinically important given increasing use of rapid molecular tests and whole genome sequencing (WGS).METHODS:We analyse data from six studies in KwaZulu-Natal, South Africa. Most patients (>75%) had baseline rifampicin resistance. Sputum was collected for culture at baseline and at between two and nine intervals until month six. Positive cultures underwent WGS. Mixed infections and reinfections were excluded from analysis.FINDINGS:Baseline Mtb overall genetic diversity (at treatment initiation or major change to regimen) was associated with cavitary disease, not taking antiretroviral therapy if HIV infected, infection with lineage 2 strains and absence of second-line drug resistance on univariate analyses. Baseline genetic diversity was not associated with six-month outcome. Genetic diversity increased from baseline to weeks one and two before returning to previous levels. Baseline genetic heteroresistance was most common for bedaquiline (6/10 [60%] of isolates with RAVs) and fluoroquinolones (9/62 [13%]). Most patients with heterozygous RAVs on WGS with sequential isolates available demonstrated RAV persistence or fixation (17/20, 85%). New RAVs emerged in 9/286 (3%) patients during treatment. We could detect low-frequency RAVs preceding emergent resistance in only one case, although validation of deep sequencing to detect rare variants is required.INTERPRETATION:In this study of single-strain Mtb infections, baseline within-host bacterial genetic diversity did not predict outcome but may reveal adaptations to host and drug pressures. Predicting emergent resistance from low-frequency RAVs requires further work to separate transient from consequential mutations.FUNDING:Wellcome Trust, NIH/NIAID.

Background Pyrazinamide (PZA) is a key component of current and future regimens for tuberculosis (TB). Inclusion of PZA at higher doses and for longer durations may improve efficacy outcomes but must be balanced against the potential for worse safety outcomes. Methods We will search for randomised and quasi-randomised clinical trials in adult participants with and without the inclusion of PZA in TB treatment regimens in the Cochrane infectious diseases group’s trials register, Cochrane central register of controlled trials (CENTRAL), MEDLINE, EMBASE, LILACS, the metaRegister of Controlled Trials (mRCT) and the World Health Organization (WHO) international clinical trials registry platform. One author will screen abstracts and remove ineligible studies (10% of which will be double-screened by a second author). Two authors will review full texts for inclusion. Safety and efficacy data will be extracted to pre-piloted forms by one author (10% of which will be double-extracted by a second author). The Cochrane risk of bias tool will be used to assess study quality. The study has three objectives: the association of (1) inclusion, (2) dose and (3) duration of PZA with efficacy and safety outcomes. Risk ratios as relative measures of effect for direct comparisons within trials (all objectives) and proportions as absolute measures of effect for indirect comparisons across trials (for objectives 2 and 3) will be calculated. If there is insufficient data for direct comparisons within trials for objective 1, indirect comparisons between trials will be performed. Measures of effect will be pooled, with corresponding 95% confidence intervals and p values. Meta-analysis will be performed using the generalised inverse variance method for fixed effects models (FEM) or the DerSimonian-Laird method for random effects models (REM). For indirect comparisons, meta-regression for absolute measures against dose and duration data will be performed. Heterogeneity will be quantified through the I 2 -statistic for direct comparisons and the τ 2 statistic for indirect comparisons using meta-regression. Discussion The current use of PZA for TB is based on over 60 years of clinical trial data, but this has never been synthesised to guide rationale use in future regimens and clinical trials. Systematic review registration: International Prospective Register of Systematic Reviews (PROSPERO) CRD42019138735

Objectives: The oxazolidinone linezolid is an effective component of drug-resistant TB treatment, but its use is limited by toxicity and the optimumdose is uncertain. Current strategies are not informed by clinical pharmacokinetic (PK)/pharmacodynamic (PD) data; we aimed to address this gap. Methods: We defined linezolid PK/PD targets for efficacy (fAUC(0-24): MIC > 119 mg/L/h) and safety (fC(min)< 1.38mg/L). We extracted individual-level linezolid PK data from existing studies on TB patients and performed meta-analysis, producing summary estimates of fAUC(0-24) and fCmin for published doses. Combining these with a published MIC distribution, we performed Monte Carlo simulations of target attainment. Results: The efficacy target was attained in all simulated individuals at 300mg q12h and 600mg q12h, but only 20.7% missed the safety target at 300mg q12h versus 98.5% at 600mg q12h. Although suggesting 300mg q12h should be used preferentially, these data were reliant on a single centre. Efficacy and safety targets were missed by 41.0% and 24.2%, respectively, at 300mg q24h and by 44.6% and 27.5%, respectively, at 600mg q24h. However, the confounding effect of between-study heterogeneity on target attainment for q24h regimens was considerable. Conclusions: Linezolid dosing at 300mg q12h may retain the efficacy of the 600mg q12h licensed dosing with improved safety. Data to evaluate commonly used 300mg q24h and 600mg q24h doses are limited. Comprehensive, prospectively obtained PK/PD data for linezolid doses in drug-resistant TB treatment are required.

Background: The ‘external validity’ of randomized controlled trials is an important measure of quality, but is often not formally assessed. Trials concerning mass drug administration for helminth control are likely to guide public health policy and careful interpretation of their context is needed. We aimed to determine how representative participants in one such trial were of their community. We explore implications for trial interpretation and resulting public health recommendations. Methods: The trial assessed was the Entebbe Mother and Baby Study (EMaBS), a trial of anthelminthic treatment during pregnancy and early childhood. In a novel approach for assessing external validity, we conducted a two-stage cluster sample community survey within the trial catchment area and compared characteristics of potentially-eligible community children with characteristics of children participating in the trial. Results: A total of 173 children aged three to five-years-old were surveyed from 480 households. Of children surveyed, we estimated that mothers of 60% would have been eligible for recruitment, and of these, 31% had actually been enrolled. Children surveyed were compared to 199 trial children in the same age group reviewed at annual trial visits during the same time period. There were significant differences in ethnicity between the trial participants and the community children, and in socioeconomic status, with those in the trial having, on average, more educated parents and higher maternal employment. Trial children were less likely to have barefoot exposure and more likely to use insecticide-treated bed nets. There were no significant differences in numbers of reported illness events over the last year. Conclusions: The trial had not enrolled all eligible participants, and those enrolled were of higher socioeconomic status, and had lower risk of exposure to the parasitic infections targeted by the trial interventions. It is possible the trial may have underestimated the absolute effects of anthelminthic treatment during pregnancy and early childhood, although the fact that there were no differences in reported incidence of common infectious diseases (one of the primary outcomes of EMaBS) between the two groups provides reassurance. Concurrent community surveys may be an effective way to test the external validity of trials. EMaBS Trial registration: ISRCTN32849447, registered 22 July 2005

An epidemic of acute hepatitis C (AHC) has been described amongst HIV-infected MSM [1–8]. Traditionally, treating AHC in this population has had clear advantages over waiting to treat in the chronic phase, with improved sustained virological response (SVR) rates and reduced length of therapy [9–12]. Treatment is offered to those who fail to demonstrate a 2 log decline at week 4 or still have detectable hepatitis C virus (HCV) RNA at week 12 and hence are unlikely to clear spontaneously [13]. The treatment of chronic HCV has been revolutionized by the advent of directly acting antivirals (DAAs) [14]. However, the role of these agents in AHC is unclear, particularly in light of the now-excellent efficacy in chronic infection. Guidelines still recommend therapy with pegylated interferon and ribavirin, and DAAs are not currently licensed for AHC [9,15]. Nonetheless, we have encountered several cases in which we have felt the use of DAAs warranted for AHC. The demographics and essentials of the HIV and AHC history of these patients are presented in Table 1.Table 1: Demographics, HIV, acute hepatitis C history and therapy for four patients treated with directly acting antivirals for acute hepatitis C.Patient 1 was monitored for 4 weeks, failed to reduce his viral load by 2 log and was thus considered for AHC therapy. He had a background of depression and was a healthcare professional in an important role. Two companies were therefore approached to access an all-oral, interferon-free DAA regimen, as DAAs were not licensed at this time, both of whom agreed to provide medication. Patient 2 presented with evidence of hepatic failure, with deranged clotting and low albumin, which failed to resolve after more than 10 days of supportive inpatient therapy. Similarly, although patient 4 had initially normal synthetic function, after a week he developed hepatic failure. Given the clinical severity and, in the case of patient 2, background of depression, we aimed to avoid interferon-based therapy and obtained access to DAAs. Patient 3 was concerned about transmission risk, keen to initiate therapy and had access to DAAs privately. All patients were commenced on Harvoni, a fixed dose combination of 90 mg of the NS5A inhibitor ledipasvir and 400 mg of the nucleotide analogue NS5B polymerase inhibitor sofosbuvir, once per day. Length of therapy and the addition (or otherwise) of ribavirin was based on current understanding of the length of therapy required for AHC at the time of treatment initiation, HCV RNA viral load and evidence of underlying liver disease; with patient 1 (low viral load, no underlying liver disease and prior to evidence for the possible efficacy of shorter courses [16]) receiving 12 weeks of Harvoni alone, patients 2 and 4 (high viral load and evidence of underlying liver disease on the basis of Fibroscan or liver biopsy) commencing 12 weeks of Harvoni and ribavirin and patient 3 (modest viral load, no underlying liver disease and after publication of evidence for the possible efficacy of shorter courses [16]) receiving only 8 weeks of Harvoni. Three patients (1, 2 and 4) were receiving protease inhibitor therapy for their HIV infection at the time of the AHC diagnosis. To minimize any potential drug–drug interactions and reduce any liver toxicity, patients 1 and 2 had their HIV therapy switched to integrase inhibitor based therapy (Truvada and Raltegravir in the case of patient 1 and Triumeq, after a 3-week pause to allow liver function test recovery, in the case of patient 4). Patient 2 had extensive previous antiretroviral exposure and current hepatic failure, and hence antiretrovirals were discontinued until complete normalization of liver function tests and completion of DAA therapy, at which point, the same antiretrovirals were recommenced. Patient 3 was receiving an non-nucleoside reverse-transcriptase inhibitor-based regimen and had only a modest alanine transaminase (ALT) rise and hence remained on the same antiretrovirals throughout. Aside from patient 2, who had to discontinue ribavirin after 2 weeks due to nausea, all patients had an uncomplicated follow-up, requiring only three to five short visits. Liver function tests and HCV RNA monitoring were variable and dictated by clinical need, all patients had no detectable HCV RNA and normal ALT by week 8, and those with lower baseline HCV RNA became undetectable sooner. Patients 1, 2 and 4 have achieved an SVR12, and patient 3 has achieved an SVR4. The optimum regimen and duration of therapy for AHC are unclear, particularly in the light of recent, poorer than expected results, for both 6- and 12-week regimens of sofosbuvir and ribavirin [17,18]. However, our experience offers proof of principle for well tolerated, all-oral DAA therapy with Harvoni (with and without ribavirin) across a range of clinical situations and with minimal follow-up.

#### The bottom line Tuberculosis remains a major cause of morbidity and mortality globally, with an estimated nine million people developing the disease and 1.5 million deaths in 2013; equating to 4100 deaths a day.1 Nevertheless, considerable gains have been made in international tuberculosis control; incidence rates are decreasing (albeit slowly) and mortality has been reduced by 45% worldwide. The advent of multidrug resistant tuberculosis threatens this progress. In this review we detail the challenges faced globally in the diagnosis, treatment, and control of multidrug resistant tuberculosis and why this matters to high and low burden multidrug resistant tuberculosis settings alike. #### Sources and selection criteria We searched Medline, Embase, and Scielo with the terms “MDR TB”, “Tuberculosis, Multidrug-Resistant”. We also reviewed the World Health Organization Global Tuberculosis Report 2014 and other national tuberculosis programme reports. We included data from systematic reviews/meta-analyses, randomised controlled trials, and good quality observational studies focused on multidrug resistant tuberculosis. Rifampicin and isoniazid form the backbone of conventional first line treatment for tuberculosis. Multidrug …