Some antibiotics are effective against only certain types of bacteria. Others can effectively fight a wide range of bacteria. Antibiotics weaken or destroy bacteria. Antibiotics do this by interfering with the protein formation of bacteria. Various types of antibiotics work either by directly attacking an existing infection or by preventing a new infection from growing.
Bacteria can become resistant to an antibiotic that had previously been effective.
Bacteria are most likely to develop resistance after long-term treatments with an antibiotic or with antibiotics that kill a wide variety of bacteria. Resistance is a growing problem, and there are concerns that some types of bacterial infections will eventually become immune to most antibiotics and will not be treatable. This resistance is attributed to excessive use of antibiotics, especially for common infections. This over use is believed to help create new strains of resistant bacteria. This is why it is so important to use antibiotics for only bacterial infections.