Tuberculosis. Coloured X-ray of the chest of a male patient with pulmonary tuberculosis (TB). The affected areas of the lungs are red. Pulmonary tuberculosis is caused by the bacterium Mycobacterium tuberculosis, which is spread by coughing and sneezing. The bacteria create primary tubercles, nodular lesions of dead tissue and bacteria, when inhaled into the lungs. Pulmonary tuberculosis may be symptomless, and may recur at periods when the patient's immune system is weakened. Symptoms include fever, weight loss and the coughing up of blood. Treatment is with long-term antibiotics.