Light micrograph of a cluster of Mycobacterium tuberculosis, the rod-like bacilli bacteria that cause tuberculosis in humans. This bacterium forms filamentous, branching structures, which are inhaled into the lungs in airborne droplets to form a primary tubercle, an initial focus of infection; spread takes place via adjacent lymph nodes. This form is called pulmonary tuberculosis or consumption (wasting). It is a disease still fatal to those in poor countries suffering lowered resistance and malnutrition. The bacteria are transmitted from infected patients by coughing or sneezing. Mag: x320 at 6x4.5cm, x192 at 35mm size.