Depends a lot on the antibiotic and the bacteria. For example, many of the anti-TB drugs require a long course, because mycobateria are very slow growing, and s

Depends a lot on the antibiotic and the bacteria. For example, many of the anti-TB drugs require a long course, because mycobateria are very slow growing, and so don't take up the antibiotics that will kill them at all quickly. Speaking as an ex-microbiologist.