Antibiotics are drugs prescribed by your health care provider to fight infections caused by bacteria. Antibiotics slow the spread of infection so that a person's own body can fight off the infection. Some of the drugs slow the growth of bacteria and allow the person to fight off the bacteria. Other antibiotics kill the bacteria.
Antibiotics only work against bacteria.
Virus infections, such as colds and flu, cannot be treated with antibiotics. An antibiotic should be taken when prescribed by your health care provider for an illness known or thought to be caused by bacteria. Your health care provider may try a higher dose of the antibiotic, a different antibiotic, or may find that either a virus or bacteria that are resistant to the antibiotic caused your infection. It means that the bacteria has genetically changed so that the antibiotic is no longer capable of slowing the growth or killing it. When this happens, you continue to be sick.