In reality, many antimicrobials have a relative toxicity. Antimicrobial is a broader category that includes antifungal, antiviral, antiprotozoal or antibacterial compounds. Antibacterials specfically act against bacterial cells. The actual mechanism of antibacterial compounds is not always known. The penicillin class of antibiotics is a diverse, yet highly essential class of antibiotics.
Penicillins work by damaging the cell wall of the bacteria.
Penicillin and all of its derivatives come from a mold, Penicillium notatum , which is toxic bluish-green mold often found on old bread. The mold must be carefully processed to produce the penecillin. With the emergence of drug-resistant microrganisms, drug treatments that used to be effective have become less effective against certain bacteria, and in some cases, not effective at all. For example, simple penicillin V or other penicillins cannot always be used by themselves to treat a particular infection. In these cases, the microorganism is capable of disabling the drug and making it ineffective.