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Antibiotic combination therapies are an approach used to counter the evolution of resistance; their purported benefit is they can stop the successive emergence of independent resistance mutations in the same genome. Here, we show that bacterial populations with 'mutators', organisms with defects in DNA repair, readily evolve resistance to combination antibiotic treatment when there is a delay in reaching inhibitory concentrations of antibiotic—under conditions where purely wild-type populations cannot. In populations of Escherichia coli subjected to combination treatment, we detected a diverse array of acquired mutations, including multiple alleles in the canonical targets of resistance for the two drugs, as well as mutations in multi-drug efflux pumps and genes involved in DNA replication and repair. Unexpectedly, mutators not only allowed multi-resistance to evolve under combination treatment where it was favoured, but also under single-drug treatments. Using simulations, we show that the increase in mutation rate of the two canonical resistance targets is sufficient to permit multi-resistance evolution in both single-drug and combination treatments. Under both conditions, the mutator allele swept to fixation through hitch-hiking with single-drug resistance, enabling subsequent resistance mutations to emerge. Ultimately, our results suggest that mutators may hinder the utility of combination therapy when mutators are present. Additionally, by raising the rates of genetic mutation, selection for multi-resistance may have the unwanted side-effect of increasing the potential to evolve resistance to future antibiotic treatments. Author summary: The global rise in antimicrobial resistance means we urgently need new approaches that halt its spread. Combination therapy, using multiple antibiotics as one treatment, proposes to do just that. Evolving resistance to combinations should be exceedingly rare, as it requires multiple mutations to occur in the same genetic background before microbial growth is inhibited. We find that wild-type bacteria cannot achieve this, even when inhibition does not occur rapidly. However, we show that introducing a small number of 'mutators' defective in DNA repair allows multi-drug resistance to readily evolve during both single-drug and combination treatments. As mutators are common in natural populations and infections, our results suggest that combination therapy may not be as resilient against resistance evolution as once thought. [ABSTRACT FROM AUTHOR]

Background: Levofloxacin is a preferred drug for multidrug-resistant (MDR)-tuberculosis (TB) with bactericidal activity that correlates with the pharmacokinetic exposures of serum peak concentration (Cmax) and total area under the concentration time curve (AUC0-24). Pharmacokinetic exposures can be measured to personalize dosing to reach targets, but this practice requires venepuncture, chromatographic or mass spectrometry equipment, and technical expertise. We sought to demonstrate the accuracy of using urine colorimetry as a more feasible estimation of levofloxacin exposure. Method: A colorimetric method using bromocresol green was tested on spiked urine samples with levofloxacin measured using a spectrophotometer. This method was tested in urine samples of healthy volunteers given one 750 mg dose of levofloxacin with urine collected at 0–4 h, 4–8 h, and 8–24 h intervals, and concomitant serum samples were collected and analyzed by high-performance liquid chromatography. Validation of this assay was done in a cohort of people living with human immunodeficiency virus (PLWH), initiating a levofloxacin containing MDR-TB regimen. Results: Urine colorimetry was reproducible in spiked samples and the calibration was curve linear for levofloxacin concentrations ranging from 7.8 μg/ml to 250 μg/ml, with r = 0.98. In healthy volunteers, correlation between urine absorbance values and serum AUC0-24 was highest in urine collected between 4 and 8 h (r = 0.91, P = 0.01), yet in PLWH, urine collected between 0 and 4 h had highest correlation (r = 0.66, P = 0.05). The area under the receiver operating characteristics curve was >0.8 in the derivation, as well as the validation cohort for the urine absorbance values identifying people with total serum exposure below target. Conclusion: Urine colorimetry was highly sensitive in predicting target serum concentrations. Colorimetric methods to determine levofloxacin in urine may improve the feasibility of therapeutic drug monitoring and personalized dose adjustment in TB endemic settings. [ABSTRACT FROM AUTHOR]

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Introduction: Completion of anti-tuberculosis (TB) treatment is of paramount importance for TB patients, as well as for the global efforts of TB control. However, there is neither a gold-standard measure to monitor adherence to TB treatment nor a widely used definition for different levels of adherence. Areas covered: in this review we aim to describe the different methods used to measure patients' adherence to anti-TB treatment, identifying their main strengths and limitations, with a focus on low resource settings. Expert commentary: there is a need for continuing the quest for a low cost, reliable and acceptable measure of adherence to TB treatment. We should harmonize treatment adherence measurement to allow adequate comparison of different interventions aimed at increasing adherence to TB treatment, although the way we ensure adherence can affect adherence endpoints themselves. The accuracy of adherence measurement is of importance in the context of drug clinical development. [ABSTRACT FROM AUTHOR]