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Latent tuberculosis infection (LTBI) constitutes an important public health problem because of risk of progression to TB disease. Effective treatment of multi-drug resistant (MDR) LTBI would prevent progression to MDR TB disease, which would improve patient and public health outcomes. The majority of MDR LTBI treatment studies have focused on the use of fluoroquinolone-based antibiotic regimens. Options for and experience in the treatment of fluoroquinolone-resistant MDR LTBI are limited in the published literature and not comprehensively addressed in current guidelines. In this review, we share our experience with the treatment of fluoroquinolone-resistant MDR LTBI with linezolid. We discuss treatment options for MDR TB that provide context for predicting effective MDR LTBI treatment, with a focus on the microbiologic and pharmacokinetic properties of linezolid that support its use. We then summarize the evidence for treatment of MDR LTBI. Finally, we present our experiences treating fluoroquinolone-resistant MDR LTBI with linezolid with an emphasis on dosing considerations to optimize efficacy and minimize potential toxicities.

Background: In 2019, the World Health Organization released guidelines reflecting major changes in multidrug-resistant tuberculosis (MDR-TB) management—prioritizing fluoroquinolones, bedaquiline, and linezolid (LZD) while de-emphasizing previously favored injectable agents. In some cases, linezolid use is associated with gastrointestinal intolerance, mitochondrial toxicity, and significant drug interactions. CDC’s Division of Tuberculosis Elimination supports a network of regional TB Centers of Excellence, which provide medical consultation to healthcare providers. Consultations are documented in a medical consultation database (MCD) enabling evaluation of management questions and recommendations. We describe the scope of clinical inquiries and responses specific to linezolid use for MDR-TB in the US. Research Question: What are the major themes of provider and patient challenges regarding the use of linezolid for the treatment of MDR-TB in the US? Methods: We queried MCD consults categorized as “MDR/XDR-TB” from 1/1/2013 to 12/31/2018. Only linezolid-specific consultations were included; incomplete and duplicate entries were excluded as were those citing linezolid historically or theoretically. Subgroup characteristics were assessed (e.g., Center, year, provider type). A descriptive coding scheme was developed through inductive thematic analysis. Results: In 2013–2018 of the 1889 consults regarding MDR/XDR-TB, 934 MDR-TB consults referenced linezolid; 137 met inclusion criteria, representing between 4 and 10% of MDR-TB consults annually. Four main themes emerged: adverse effects (71.5%); concerns about linezolid use due to co-morbidities or concurrent medication use (15.3%); dosing adjustments (8.8%); and monitoring and maintenance logistics (4.4%). Interpretations: Linezolid consults consistently exceeded 4% of all consults annually over the 6-year period, suggesting a need for access to expert opinion for providers using linezolid to manage MDR-TB. While only a snapshot of MDR-TB in the US, this evaluation summarizes major provider concerns regarding particular adverse effects, and highlights a need for evidence-based guidance regarding linezolid dosing and toxicity management.

The current tuberculosis (TB) case reporting system for the United States, the Report of Verified Case of TB (RVCT), has minimal capture of multidrug-resistant (MDR) TB treatment and adverse events. Data were abstracted in five states using the form for 13 MDR TB patients during 2012–2015. The Centers for Disease Control and Prevention Guidelines for Evaluating Public Health Surveillance Systems were used to evaluate attributes of the form. Unstructured interviews with pilot sites and stakeholders provided qualitative feedback. The form was acceptable, simple, stable, representative, and provided high-quality data but was not flexible or timely. For the 13 patients on whom data were collected, the median duration of treatment with an injectable medication was 216 days (IQR 203–252). Six (46%) patients reported a side effect requiring a medication change and eight (62%) had a side effect present at treatment completion. A standardized MDR TB supplemental surveillance form was well received by stakeholders whose feedback was critical to making modifications. The finalized form will be implemented nationally in 2020 and will provide MDR TB treatment and morbidity data in the United States to help ensure patients with MDR TB receive the most effective treatment regimens with the least toxic drugs. Keywords: Drug resistance, Surveillance, Tuberculosis