The administration of anti-infective substances, such as antibiotics, should be considered if a person is unable to overcome a bacterial infection through his own defenses. Antibiotic agents are especially designed to eliminate bacteria. They interfere with their metabolism and growth by inhibiting the synthesis of proteins or DNA, and by increasing the permeability of their cell walls or the destruction thereof. Bacteriostatic antibiotics only inhibit growth and reproduction, whereas bactericidal antibiotics kill the bacteria. Some agents are active against a wide variety of bacteria (broad-spectrum) and others only against a few specific bacteria (narrow-spectrum).

Based on chemical structures and mechanisms of action, several classes of antibiotic agents can be distinguished.

Fluoroquinolones such as ciprofloxacin or moxifloxacin are bactericidal, broad-spectrum antibiotics that inhibit DNA gyrase, an enzyme required for repair, growth, and reproduction mechanisms of the bacteria. These potent antibiotics with excellent tissue penetration are effective against a wide range of bacteria, including many that are difficult to treat.

Penicillins, beta-lactam antibiotics, are a group of bactericidal antibiotics and provide either small spectrum or broad spectrum activity. They attach to bacterial enzymes (penicillin- binding proteins) inhibiting the synthesis of the cell wall and thus, usually result in cell resolution. Some bacteria have developed resistance by producing an enzyme (penicillinase) which destroys the beta-lactam structure.

Cephalosporins, younger beta-lactam antibiotics, were developed to treat penicillin-resistant infections. They also work by destroying the cell walls of bacteria. Cephalosporins can be divided in four generations depending on their spectrum of activity.

Aminoglycosides are effective bactericidal antibiotics in the treatment of serious, gram-negative infections. They interfere with the synthesis of proteins which are vital for the cell.

Macrolides are narrow-spectrum antibiotics, which have predominantly bacteriostatic activity inhibiting protein synthesis in the bacteria.

Tetracyclines interfere with bacteria by inhibiting protein synthesis. They have good tissue penetration and are effective against many gram-positive and gram-negative bacteria.

Glycopeptides, such as vancomycin, inhibit cell wall synthesis. They are active against aerobic and anaerobic gram-positive bacteria, but not against gram-negative bacteria. They mainly are used in combination with other antibiotics in severe infections.