Abstract Bacteria are developing resistance to antibiotics more quickly than people can develop new antibiotics. Moreover, resistance can spread between individual bacteria of the same species or between individuals of different species when genes encoding resistance mechanisms are passed between bacteria.
Resistant bacteria develop a variety of mechanisms to dodge the antibiotic bullet.
Some bacteria unleash enzymes that can dismantle antibiotics such as the -lactams, aminoglycosides, chloramphenicol and tetracycline before they even enter the bacteria cell. The enzymes can also chew up the antibiotics if they do enter. Sometimes, bacteria develop pumps that shunt antibiotics such as tetracycline and erythromycin out of the cell. Another tactic is to alter the shapes of a bacterial molecule to which the antibiotics erythromycin or tetracycline must bind. In some cases, bacterial metabolic enzymes that would be inhibited by antibiotics such as the sulfonamides or trimethoprim can become altered so that they continue to function in spite of the presence of antibiotics.