The perspective of local microbiologies brings attributes of microbes squarely into the anthropological purview, underscoring dialectics of biology and culture in which infectious diseases--and knowledge and practices about them--are produced. In this article I provide an anthropological perspective of expert discourses about tuberculosis at a tuberculosis reference laboratory in Tbilisi, Georgia. A latent-active dichotomy prevails in contemporary global health responses to tuberculosis. Based on ethnographic research about everyday laboratory-based diagnostic work, I question the stability of this dichotomy and unsettle biological and cultural reductionism. In so doing, I highlight the theoretical and methodological contributions that anthropological engagements with science, technology, and medicine bring to studies of global health.