Transmission Links and Clinical Spectrum of Exhaled Mycobacterium Tuberculosis

PROJECT ABSTRACT Tuberculosis (TB) continues to pose a significant global public health challenge, with persistent burden of over 10 million incident cases likely perpetuated by millions of undiagnosed/unreported TB cases contributing to global transmission. We recently observed an unexpected rate of viable Mycobacterium tuberculosis (Mtb) aerosolization among individuals in a high burden TB setting who test negative for Mtb in their sputum. In response to RFA AI-24-049 Halting Tuberculosis (TB) Transmission, this study aims to investigate the role of sputum-negative, Mtb breath-positive individuals in transmission and characterize their underlying clinical spectrum. We will use original breath sampling techniques combined with an Mtb viability assay, highly- sensitive molecular methods, and longitudinal clinical phenotyping with high-resolution imaging to address two specific aims. First, we will assess the association between Mtb breath shedding and transmission. Specifically, we will assess the prevalence of sputum-negative individuals who shed viable Mtb in their breath across high and low TB burden settings. We will then estimate their prevalence in transmission clusters by genotypically linking single nucleotide polymorphisms in exhaled Mtb strains to sequenced Mtb isolates of sputum-positive household members. To estimate infectiousness, we will compare the IGRA positivity rates of child household contacts in sputum-negative, Mtb breath-positive households to those in exclusively sputum-negative, Mtb breath-negative households. Secondly, we aim to examine the extent to which sputum-negative exhaled Mtb reflects underlying pathology, immune activation, and disease progression versus regression over time. We will thus characterize the clinical spectrum of sputum-negative exhaled Mtb through high-resolution CT imaging, immune response markers, and detailed longitudinal evaluations over 12 months. By integrating breath sampling, genotyping, and clinical evaluations, this study will provide critical insights into a potential hidden reservoir of undiagnosed TB transmission. These findings would directly guide comprehensive and early/preventive diagnostic strategies for the missing millions on the undiagnosed TB spectrum, in turn reducing the global burden of TB disease and transmission.