Usually bacteriostatic, but bactericidal against some organisms. Affects ribosomal function. Macrolides Derived from propionate. 1952 clarithromycin, azithromycin, and dirithromycin 1990s Bacteriostatic Lincosamines Derived from amino acids and carbohydrates. 1947 Affect bacterial cell membranes.
All antibiotics can cause hypersensitivity reactions.
Penicillins produce most hypersensitivity reactions. Resistance transfer is the most common mechanism, and was only discovered in 1963. Organisms manifest resistance in a multitude of ways. The problem here is that one risks underdosing which leads to treatment failure and emergence of resistant strains. Media and conditions are variable and may not reflect in vivo conditions.