Antibiotics are strong medicines that fight bacterial infections either by killing the bacteria or preventing it from reproducing. Patients should be cautious with antibiotic use because they are ineffective against viral infections. Antibiotics include many different families of drugs that are categorized according to their chemical structure. Doctors prescribe a particular antibiotic based upon their knowledge of what is effective for a particular type of bacteria or condition.
Mechanism of Action
Different families of antibiotics have different mechanisms of action. The Alliance of Prudent Use of Antibiotics out of Tufts University explains that penicillins, bacitracin, cephalosporins and drugs like vancomycin interfere with the development of the bacterial cell wall. Other antibiotics such as chloramphenicol, erythromycin and the tetracyclines work by inhibiting protein synthesis by attaching to the bacterial ribosome. Still other antibiotics such as rifampin and the quinolones block the synthesis of bacterial RNA or DNA.
All of the drugs in these families can also be categorized as either systemic or topical, depending on how they are administered.
Topical Antibiotics
Topical antibiotics are those that are applied directly to the skin or to the eyes. Some topical antibiotics are available in over-the-counter preparations to treat minor scrapes and wounds. These preparations include creams and ointments made from neomycin, polymyxin and bacitracin. Other preparations are available by prescription.
Bacitracin and mupirocin are particularly effective against open infections such as infected eczema and infected dermal ulcers as well as nasal infections. Retapamulin, another topical antibiotic, is helpful with a common skin infection called impetigo. Mupirocin and retapamulin are only available by prescription while bacitracin is available over the counter.
Systemic Antibiotics
Systemic antibiotics are those that are given orally or intravenously to treat a whole host of different conditions. Intravenous antibiotics are routinely given to treat septic shock, a disease in which the patient's body becomes so over-ridden with bacteria that the blood pressure becomes dangerously low. Oral antibiotics are given with specific instructions for their use. Patients need to follow these directions and take the entire prescription or antibiotic resistance can occur.
Antibiotic Resistance
Mayo Clinic experts explain that "bacteria live on the evolutionary fast track." Since they reproduce so quickly, the characteristics of a strain of bacteria can change relatively rapidly. Any bacteria that survives antibiotic use can give rise to a new antibiotic-resistant strain. Antibiotics first became mass produced by drug companies in the early 1940s. Since that time, many new strains of resistant bacteria have evolved, necessitating the development of new and stronger antibiotics.
MRSA
MRSA stands for methicillin-resistant staphylococcus aureus. Although this "superbug" was long known in hospitals and other medical settings, it has been appearing with alarming frequency outside of these settings. MRSA infections often appear on the skin as open wounds, pimples and sores. In other instances, it can burrow deeply in the body, causing potentially life-threatening infections in bones, joints, surgical wounds, the bloodstream, heart valves and lungs. Although it can be treated with the antibiotic vancomycin, it is only a matter of time before vancomycin-resistant strains develop.
