Broad-spectrum antibiotic their greater potential to disrupt a larger variety of normal human flora. After continued exposure to an antibiotic, bacteria may develop changes in their structure or function that make them resistant to the antibiotic. These resistant organisms will live, while the susceptible organisms will die, leaving the population of bacteria entirely resistant to a given antibiotics. For example, after the discovery of penicillin and its subsequent use to treat bacterial infections, bacteria were found to have begun producing an enzyme, penicillinase, which rendered the penicillin molecule inactive. In response to this newly-acquired resistance, newer penicillins were produced that could not
Antibiotic synergy potential therapies is moving in three primary directions. Some research is devoted to finding combinations of extant antibiotics which when combined exhibit synergy. A classic example of this effect is the interaction between β-lactams, which damage the bacteria cell membrane, and aminoglycosides, which inhibit protein synthesis. The damage dealt to the cell wall by β-lactams allows more aminoglycoside molecules to be taken up into the cell than would otherwise be possible, enhancing cell damage. In some cases, antibacterial combinations restore potency to ineffective drugs. Other research has been devoted to finding antibiotic resistance breakers (ARB's) which enhance an antibiotic's potency.