Overview of antibacterial drugs

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Antibacterial drugs are derived from bacteria or molds or are synthesized de novo. Technically, “antibiotic” refers only to antimicrobials derived from bacteria or molds but is often (including in THE MANUAL) used synonymously with “antibacterial drug.”
(See also Antibiotics in Neonates.)
Antibiotics have many mechanisms of action, including the following:

Inhibiting cell wall synthesis
Increasing cell membrane permeability
Interfering with protein synthesis, nucleic acid metabolism, and other metabolic processes (eg, folic acid synthesis)

Antibiotics sometimes interact with other drugs, raising or lowering serum levels of other drugs by increasing or decreasing their metabolism or by various other mechanisms (see table Some Common Effects of Antibiotics on Other Drugs). The most clinically important interactions involve drugs with a low therapeutic ratio (ie, toxic levels are close to therapeutic levels). Also, other drugs can increase or decrease levels of antibiotics.
Many antibiotics are chemically related and are thus grouped into classes. Although drugs within each class share structural and functional similarities, they often have different pharmacology and spectra of activity.