Relationship between culture conversion and clinical outcomes in nontuberculous mycobacterial pulmonary disease: Narrative review

PURPOSE: Nontuberculous mycobacterial pulmonary disease (NTMPD) is a chronic, often progressive condition associated with a significant symptom burden and increased mortality. Goals of NTMPD treatment include microbiological eradication, symptom reduction, improved quality of life (QoL), and preventing disease progression. Antibiotics are used to reduce microbial burden, and cultures of sputum are used to guide treatment. However, it is unclear whether achieving culture-negative status (often called "culture conversion") is associated with improved clinical outcomes. Studies use a variety of measures including symptom burden, radiological status, lung function, 6-min walk test distance, QoL assessments, and mortality to evaluate clinical outcomes related to changes in how patients feel, function, and survive. There is strong interest in more clearly understanding which clinical benefits may be associated with culture conversion. As NTMPD can cause sustained structural lung damage and declines in long-term pulmonary function, it is important to have clear evidence if prevention of these morbidities is associated with culture conversion. METHODS: This targeted literature review summarizes the published evidence regarding associations between sputum culture conversion and clinical outcomes in patients with NTMPD. Identified studies used varying definitions of culture conversion and treatment success, making interpretation of outcomes across studies challenging. RESULTS: Although some studies suggest an association between culture conversion and aspects of clinical improvement, overall, there are currently few high-quality studies supporting a link. CONCLUSION: Further clarification of the relationship between culture conversion and clinical outcomes would be helpful in improving clinical monitoring and therapeutic decision-making during the treatment of patients with NTMPD.