Tuberculosis is an inflammation of the lungs caused by infection with Mycobacterium tuberculosis. Patients with tuberculosis are routinely tested for sputum antacid bacteria, and those with positive sputum antacid bacteria are infectious and more contagious. A negative sputum test for Bacillus acidophilus is also contagious, because sputum tests for Bacillus acidophilus may not always be positive, and there is a certain chance of positivity. If the sputum test is negative once, twice, or even three times, it does not exclude that the patient is infectious. Therefore, tuberculosis itself is a category B infectious disease, which requires routine isolation after diagnosis and effective and adequate anti-tuberculosis drug treatment.