Antimicrobial agents and chemotherapy
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Antimicrob. Agents Chemother. · Jan 2015
Verapamil increases the bactericidal activity of bedaquiline against Mycobacterium tuberculosis in a mouse model.
Bedaquiline is a newly approved drug for the treatment of multidrug-resistant tuberculosis, but there are concerns about its safety in humans. We found that the coadministration of verapamil with subinhibitory doses of bedaquiline gave the same bactericidal effect in mice as did the full human bioequivalent bedaquiline dosing. Adding verapamil to bedaquiline monotherapy also protected against the development of resistant mutants in vivo. The adjunctive use of verapamil may permit use of lower doses of bedaquiline to be used and thereby reduce its dose-related toxicities in tuberculosis patients.
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Antimicrob. Agents Chemother. · Jan 2015
Comparative StudyContribution of the nitroimidazoles PA-824 and TBA-354 to the activity of novel regimens in murine models of tuberculosis.
New regimens based on two or more novel agents are sought in order to shorten or simplify the treatment of both drug-susceptible and drug-resistant forms of tuberculosis. PA-824 is a nitroimidazo-oxazine now in phase II trials and has shown significant early bactericidal activity alone and in combination with the newly approved agent bedaquiline or with pyrazinamide with or without moxifloxacin. While the development of PA-824 continues, a potential next-generation derivative, TBA-354, has been discovered to have in vitro potency superior to that of PA-824 and greater metabolic stability than that of the other nitroimidazole derivative in clinical development, delamanid. ⋯ The monotherapy studies demonstrated that TBA-354 is 5 to 10 times more potent than PA-824, but selected mutants are cross-resistant to PA-824 and delamanid. The combination studies revealed that TBA-354 is 2 to 4 times more potent than PA-824 when combined with bedaquiline, and when administered at a dose equivalent to that of PA-824, TBA-354 demonstrated superior sterilizing efficacy. Perhaps most importantly, the addition of either nitroimidazole significantly improved the sterilizing activities of bedaquiline and sutezolid, with or without pyrazinamide, confirming the value of each agent in this potentially universally active short-course regimen.
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Antimicrob. Agents Chemother. · Jan 2015
Randomized Controlled TrialImpact of nonlinear interactions of pharmacokinetics and MICs on sputum bacillary kill rates as a marker of sterilizing effect in tuberculosis.
The relationships between antituberculosis drug exposure and treatment effects on humans receiving multidrug therapy are complex and nonlinear. In patients on treatment, an analysis of the rate of decline in the sputum bacillary burden reveals two slopes. The first is the α-slope, which is thought to reflect bactericidal effect, followed by a β-slope, which is thought to reflect sterilizing activity. ⋯ However, isoniazid and ethambutol exposures may only be of importance when rifampin exposure is low. These findings need confirmation in larger studies. (This study has been registered at controlled-trials.com under registration no. ISRCTN80852505.).
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Antimicrob. Agents Chemother. · Jan 2015
Multicenter StudyStratification of the impact of inappropriate empirical antimicrobial therapy for Gram-negative bloodstream infections by predicted prognosis.
The bloodstream infection mortality risk score (BSIMRS) predicts the outcome of patients with Gram-negative bloodstream infections (BSI) with high discrimination. This retrospective cohort study examined the impact of inappropriate antimicrobial therapy on mortality in adult patients with Gram-negative BSI admitted to Palmetto Health Hospitals in Columbia, SC, USA, from 1 January 2011 to 31 December 2012 after stratification by predicted prognosis at initial presentation using BSIMRS. A multivariate Cox regression model was used to identify independent risk factors for 28-day mortality overall and within each predefined BSIMRS category (<5, 5 to 9, and ≥ 10). ⋯ RRR, ARR, and NNT were 0.25, 0.02, and 63 for BSIMRS of <5; 0.56, 0.32, and 3 for BSIMRS of 5 to 9; and 0.39, 0.39, and 3 for BSIMRS of ≥ 10, respectively. There is a significant benefit from appropriate antimicrobial therapy in patients with Gram-negative BSI with guarded (BSIMRS of 5 to 9) and poor (BSIMRS of ≥ 10) predicted prognosis. Survival difference remains unclear among those with good predicted prognosis (BSIMRS of <5) at initial presentation.
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Antimicrob. Agents Chemother. · Jan 2015
In vitro and in vivo activities of the nitroimidazole TBA-354 against Mycobacterium tuberculosis.
Nitroimidazoles are a promising new class of antitubercular agents. The nitroimidazo-oxazole delamanid (OPC-67683, Deltyba) is in phase III trials for the treatment of multidrug-resistant tuberculosis, while the nitroimidazo-oxazine PA-824 is entering phase III for drug-sensitive and drug-resistant tuberculosis. TBA-354 (SN31354[(S)-2-nitro-6-((6-(4-trifluoromethoxy)phenyl)pyridine-3-yl)methoxy)-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazine]) is a pyridine-containing biaryl compound with exceptional efficacy against chronic murine tuberculosis and favorable bioavailability in preliminary rodent studies. ⋯ In vitro studies suggest a low risk of drug-drug interactions. Low-dose aerosol infection models of acute and chronic murine tuberculosis reveal time- and dose-dependent in vivo bactericidal activity that is at least as potent as that of delamanid and more potent than that of PA-824. Its superior potency and pharmacokinetic profile that predicts suitability for once-daily oral dosing suggest that TBA-354 be studied further for its potential as a next-generation nitroimidazole.