In structure these drugs are analogues of p-amino benzoic acid Different types of antimicrobial drugs are as follows :
1 . Antibiotics
These are the substances ( produced wholly or partially by chemical synthesis ) which in low concentrations inhibit the growth of microorganisms or destroy them by intervening in their metabolic processes .
Antibiotics are products of microbial growth and thus , antibiotic therapy has been likened to setting one thief against another ‟.
Antibiotics are of two types :
1 . Bactericidal antibiotics have cidal ( killing ) effect on microbes . For example , penicillin , ofloxacin , amino glycosides , etc .
2 . Bacteriostatic antibiotics have a static ( inhibitory ) effect on microbes . For example , erythromycin , tetracycline , chloramphenicol , etc