Christine Bernard

Compassionate Use of Bedaquiline for the Treatment of Multidrug-Resistant and Extensively Drug-Resistant Tuberculosis: Interim Analysis of a French Cohort

BACKGROUND Bedaquiline is a new antibiotic that was approved for the treatment of multidrug-resistant (MDR) tuberculosis. We aimed to evaluate the short-term microbiological efficacy and the tolerability profile of bedaquiline. METHODS We performed a retrospective cohort study among patients with MDR tuberculosis receiving bedaquiline for compassionate use between January 2010 and July 2013 and evaluated at 6 months of bedaquiline treatment. RESULTS A total of 35 patients with MDR tuberculosis were included in the study. Nineteen (54%) had extensively drug-resistant (XDR) tuberculosis, and 14 (40%) had isolates resistant to fluoroquinolones (Fqs) or second-line injectables. Bedaquiline was associated with a median of 4 (range, 2-5) other drugs, including linezolid in 33 (94%) cases. At 6 months of bedaquiline treatment, culture conversion was achieved in 28 of 29 (97%) cases with culture-positive pulmonary tuberculosis at bedaquiline initiation. Median time to culture conversion was 85 days (range, 8-235 days). Variables independently associated with culture conversion were treatment with a Fq (P = .01), absence of lung cavities (P < .001), and absence of hepatitis C virus infection (P = .001). A total of 7 patients (20%) experienced a ≥60-ms increase in QT interval, leading to bedaquiline discontinuation in 2 (6%) cases. Severe liver enzyme elevation occurred in 2 patients (6%). During the study period, 1 death (3%) occurred and was reported as unrelated to tuberculosis or antituberculosis treatment. CONCLUSIONS The use of bedaquiline combined with other active drugs has the potential to achieve high culture conversion rates in complicated MDR and XDR tuberculosis cases, with a reassuring safety profile at 6 months of treatment.

Long-term outcome and safety of prolonged bedaquiline treatment for multidrug-resistant tuberculosis

Bedaquiline, a recently approved drug for the treatment of multidrug-resistant tuberculosis (MDR-TB), is recommended for a duration of 24 weeks. There are scarce data on patients treated with this drug outside clinical trials. All MDR-TB patients who started treatment from January 1, 2011 to December 31, 2013 and received ≥30 days of bedaquiline were included in a multicentre observational cohort. Among 45 MDR-TB patients, 53% harboured isolates resistant to both fluoroquinolones and second-line injectables, and 38% harboured isolates resistant to one of these drug classes. Median bedaquiline treatment duration was 361 days and 33 patients (73%) received prolonged (>190 days) bedaquiline treatment. Overall, 36 patients (80%) had favourable outcome, five were lost to follow-up, three died, and one failed and acquired bedaquiline resistance. No cases of recurrence were reported. Severe and serious adverse events were recorded in 60% and 18% of patients, respectively. Values of Fridericia-corrected QT interval (QTcF) >500 ms were recorded in 11% of patients, but neither arrhythmias nor symptomatic cardiac side-effects occurred. Bedaquiline was discontinued in three patients following QTcF prolongation. No significant differences in outcomes or adverse events rates were observed between patients receiving standard and prolonged bedaquiline treatment. Bedaquiline-containing regimens achieved favourable outcomes in a large proportion of patients. Prolonged bedaquiline treatment was overall well tolerated in this cohort. Treatment regimens including prolonged bedaquiline use are effective and overall well tolerated in MDR-TB patients http://ow.ly/vhtl305CYJj

Molecular Diagnosis of Fluoroquinolone Resistance in Mycobacterium tuberculosis

ABSTRACT As a consequence of the use of fluoroquinolones (FQ), resistance to FQ has emerged, leading to cases of nearly untreatable and extensively drug-resistant tuberculosis. Mutations in DNA gyrase represent the main mechanism of FQ resistance. A full understanding of the pattern of mutations found in FQ-resistant (FQr) clinical isolates, and of their proportions, is crucial for improving molecular methods for the detection of FQ resistance in Mycobacterium tuberculosis. In this study, we reviewed the detection of FQ resistance in isolates addressed to the French National Reference Center for Mycobacteria from 2007 to 2012, with the aim of evaluating the performance of PCR sequencing in a real-life context. gyrA and gyrB sequencing, performed prospectively on M. tuberculosis clinical isolates, was compared for FQ susceptibility to 2 mg/liter ofloxacin by the reference proportion method. A total of 605 isolates, of which 50% were multidrug resistant, were analyzed. The increase in FQr strains among multidrug-resistant (MDR) strains during the time of the study was alarming (8% to 30%). The majority (78%) of the isolates with gyrA mutations were FQr, whereas only 36% of those with gyrB mutations were FQr. Only 12% of the FQr isolates had a single mutation in gyrB. Combined gyrA and gyrB sequencing led to >93% sensitivity for detecting resistance. The analysis of the four false-positive and the five false-negative results of gyrA and gyrB sequencing illustrated the actual limitations of the reference proportion method. Our data emphasize the need for combined gyrA and gyrB sequencing in the investigation of FQ susceptibility in M. tuberculosis and challenge the validity of the current phenotype-based approach as the diagnostic gold standard for determining FQ resistance.

Rapid emergence of Mycobacterium tuberculosis bedaquiline resistance: lessons to avoid repeating past errors

Bedaquiline (BDQ) has demonstrated potent clinical activity against multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis complex strains [1–3]. It has now been used in >50 countries, and it is estimated that ∼2500 patients had been treated with BDQ by the end of 2015. In spite of its recent clinical use, there are few reports of BDQ-resistant strains [4, 5]. Mutations in the rv0678 gene encoding the MmpL5 efflux pump repressor generate low-level BDQ resistance and clofazimine (CFZ) cross-resistance [6]. To our knowledge, this is the sole mechanism of BDQ resistance described in clinical strains [4, 5]. Despite its introduction in France in 2011 for XDR- and MDR-tuberculosis (TB) treatment, we report herein four BDQ-resistant cases, and discuss strategies to avoid a surge of BDQ resistance. Bedaquiline resistance appears rapidly both after treatment and in patients that have never been treated http://ow.ly/mxEM30604OF

Molecular Analysis of the embCAB Locus and embR Gene Involved in Ethambutol Resistance in Clinical Isolates of Mycobacterium tuberculosis in France

ABSTRACT Modification of codon 306 in embB is regarded as the main mechanism leading to ethambutol (ETB) resistance in clinical isolates of Mycobacterium tuberculosis. However, numerous mutations elsewhere in the embCAB locus and in embR, a putative transcriptional activator of this locus, have been reported to be involved in ETB resistance. Here, we investigated the diversity of nucleotide variations observed in embCAB and embR in M. tuberculosis complex isolates from France. These regions were sequenced in 71 ETB-resistant (ETB-R) and 60 ETB-susceptible (ETB-S) clinical isolates of known phylogenetic lineages. The 131 isolates had 12 mutations corresponding to phylogenetic markers. Among the 60 ETB-S isolates, only 3 (5%) had nonsynonymous mutations that were not phylogenetic markers. Among the 71 ETB-R isolates, 98% had mutations in embCAB that likely contribute to ETB resistance: 70% had mutations located in embB codon 306, 406, or 497; 13% had mutations located outside these three positions between codons 296 and 426; and 15% had mutations corresponding to mutations in the embC-embA intergenic region. We found a strong association between resistance to ETB and the presence of mutations in embB and the embC-embA intergenic region (P < 0.001). In contrast, the mutations detected in embC and embA were not involved in ETB resistance, and no mutation was detected in embR. These results strongly suggest that the sensitivity of diagnostic assays for detecting ETB resistance based on testing of embB codon 306 can be increased by testing of the embB region between codons 296 and 497 and by including the embC-embA intergenic region between positions −8 and −21.

Are moxifloxacin and levofloxacin equally effective to treat XDR tuberculosis

Background Moxifloxacin retains partial activity against some fluoroquinolone-resistant mutants of Mycobacterium tuberculosis . Levofloxacin is presumed to be as active as moxifloxacin against drug-susceptible tuberculosis and to have a better safety profile. Objectives To compare the in vivo activity of levofloxacin and moxifloxacin against M. tuberculosis strains with various levels of fluoroquinolone resistance. Methods BALB/c mice were intravenously infected with 10 6 M. tuberculosis H37Rv and three isogenic mutants: GyrA A90V, GyrB E540A and GyrB A543V. Treatment with 50 or 100 mg/kg levofloxacin and 60 or 66 mg/kg moxifloxacin was given orally every 6 h, for 4 weeks. Results Levofloxacin 50 and 100 mg/kg q6h and moxifloxacin 60 and 66 mg/kg q6h generated AUCs in mice equivalent to those of levofloxacin 750 and 1000 mg/day and moxifloxacin 400 and 800 mg/day, respectively, in humans. Moxifloxacin 60 and 66 mg/kg q6h had bactericidal activity against strain H37Rv (MIC ≤ 0.25 mg/L) and mutants GyrB E540A and GyrB A543V (MIC = 0.5 mg/L). Against mutant GyrA A90V (MIC = 2 mg/L), moxifloxacin 60 mg/kg q6h did not prevent bacillary growth, whereas 66 mg/kg q6h had bacteriostatic activity. Levofloxacin 50 mg/kg q6h had bactericidal activity against H37Rv (MIC ≤ 0.25 mg/L) but not against the mutant strains. Levofloxacin 100 mg/kg q6h had bactericidal activity against H37Rv and mutants GyrB E540A (MIC = 0.5 mg/L) and GyrB A543V (MIC= 1 mg/L) but not against mutant GyrA A90V (MIC = 4 mg/L). Conclusions All mutations reduced fluoroquinolone activity, even those classified as susceptible according to phenotypic tests. High-dose levofloxacin is less effective than high-dose moxifloxacin against both fluoroquinolone-resistant and -susceptible M. tuberculosis strains in mice.

Evaluation of the new GenoType NTM-DR kit for the molecular detection of antimicrobial resistance in non-tuberculous mycobacteria

Objectives Non-tuberculous mycobacteria (NTM) are emerging pathogens causing difficult-to-treat infections. We tested a new assay (GenoType NTM-DR) that detects natural and acquired resistance mechanisms to macrolides and aminoglycosides in frequently isolated NTM species. Methods Performance was assessed on 102 isolates including reference strains [16 Mycobacterium avium , 10 Mycobacterium intracellulare , 8 Mycobacterium chimaera , 15 Mycobacterium chelonae and 53 Mycobacterium abscessus (including subsp. abscessus isolates, 18 with a t28 in erm(41) and 10 with a c28, 13 subsp. bolletii isolates and 12 subsp. massiliense isolates)]. Genotypes were determined by PCR sequencing of erm(41) and rrl for clarithromycin resistance and of the 1400-1480 rrs region for aminoglycoside resistance. Phenotypes were determined by MIC microdilution. Results GenoType NTM-DR yielded results concordant with Sanger sequencing for 100/102 (98%) isolates. The erm(41) genotypic pattern was accurately identified for M. abscessus isolates . Mutations in rrl were detected in 15 isolates (7 M. avium complex, 5 M. abscessus and 3 M. chelonae ) with acquired clarithromycin resistance harbouring rrl mutations (a2057c, a2058g, a2058t or a2059c). Mutations in rrs were detected in five isolates with amikacin resistance harbouring the rrs mutation a1408g. In two isolates, the NTM-DR test revealed an rrl mutation (initial sequencing being WT), which was confirmed by re-sequencing. The test results were concordant with phenotypic susceptibility testing in 96/102 (94.1%) isolates, with four clarithromycin-resistant and two amikacin-resistant isolates not harbouring mutations. Conclusions The GenoType NTM-DR test is efficient in detecting mutations predictive of antimicrobial resistance in M. avium complex, M. abscessus and M. chelonae.

Molecular Investigation of Resistance to Second-Line Injectable Drugs in Multidrug-Resistant Clinical Isolates of Mycobacterium tuberculosis in France

ABSTRACT The second-line injectable drugs (SLID, i.e., amikacin, kanamycin, capreomycin) are key drugs for the treatment of multidrug-resistant tuberculosis. Mutations in rrs region 1400, tlyA, and eis promoter are associated with resistance to SLID, to capreomycin, and to kanamycin, respectively. In this study, the sequencing data of SLID resistance-associated genes were compared to the results of phenotypic drug susceptibility testing by the proportion method for the SLID in 206 multidrug-resistant clinical isolates of Mycobacterium tuberculosis collected in France. Among the 153 isolates susceptible to the 3 SLID, 145 showed no mutation, 1 harbored T1404C and G1473A mutations in rrs, and 7 had an eis promoter mutation. Among the 53 strains resistant to at least 1 of the SLID, mutations in rrs accounted for resistance to amikacin, capreomycin, and kanamycin for 81%, 75%, and 44% of the isolates, respectively, while mutations in eis promoter were detected in 44% of the isolates resistant to kanamycin. In contrast, no mutations in tlyA were observed in the isolates resistant to capreomycin. The discrepancies observed between the genotypic (on the primary culture) and phenotypic drug susceptibility testing were explained by (i) resistance to SLID with MICs close to the critical concentration used for routine DST and not detected by phenotypic testing (n = 8, 15% of SLID-resistant strains), (ii) low-frequency heteroresistance not detected by sequencing of drug resistance-associated genes on the primary culture (n = 8, 15% of SLID-resistant strains), and (iii) other resistance mechanisms not yet characterized (n = 7, 13% of SLID-resistant strains).

Neither genotyping nor contact tracing allow correct understanding of multidrug-resistant tuberculosis transmission

The control of tuberculosis (TB) is challenged by the progressive increase of cases of multi-drug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). A recent European study underlined the need for data showing how TB control can be improved in terms of case finding, contact tracing, infection control and treatment to prevent further spread of MDR-/XDR-TB in the EU [1]. Even combined contact tracing and genotyping fail to explain how MDR-TB transmission occurs in one third of cases http://ow.ly/2ZKB30dRVGw

First Whole-Genome Sequence of a Clinical Isolate of Multidrug-Resistant Mycobacterium bovis BCG

ABSTRACT The attenuated BCG strain of Mycobacterium bovis is widely used as a vaccine against tuberculosis. However, in rare cases, it can be pathogenic to humans. Here, we report the first draft of a whole-genome sequence of a multidrug-resistant clinical isolate of M. bovis BCG.