It is active against a large number of Gram Positive and Gram negative pathogens including strains resistant to first generation tetracyclines. It is essentially bacteriostatic; it inhibits the bacterial protein synthesis by blocking binding of transfer RNA to the messanger RNA- ribosome complex. Lactic Acid Bacillus: Lactic acid bacilli are helpful bacteria, occurs naturally in intestine and constitute major part of the intestinal microflora.