CYCLOSERINE, TYROTHRICIN & NOVOBIOCIN



CYCLOSERINE
Broad spectrum antibiotic, also effective against many bacteria including Mycobacterium.
Being an analog of D-alanine inhibits bacterial cell wall formation by preventing d-ala-d-ala dipeptide synthesis required for formation of NAMA pentapetide (Peptidoglycon). 
TYROTHRICIN
It is a mixture of Gramocidin and Tyrocidine, obtained from B. brevis, mainly active against G +ve org., including Strepto. and Staphylo.
It acts on cell membrane and causes leakage and also uncouples oxidative phosphorylation in bac.
The drug is not absorbed orally, is too toxic for systemic use and causes hemolysis.
Used in bovine mastitis during dry period as intramammary infusion, to treat metritis and topically for skin and ear infections.
It does not cause hypersensitivity reactions.
 

NOVOBIOCIN
Obtained biosynthetically from  2 actinomycetes viz., Streptomyces niveus and S.spheroides.
It is narrow spectrum antibiotic, mainly bacteriostatic and cidal at high concentrations.
Mainly active against G +ve bac. And some strains of Proteus, Pseudomonas and Pasteurella multocida.
Acts by spincer attack both by interfering the bac. Cell memb. Permeability as well as by inhibiting cell wall synthesis.
Synergistic with tetracyclines.
Used mainly in combination with penicllin and other drugs for the Rx of mastitis in bovines.
Though it has good efficacy against Anthrax, various Streptococcal and staphylococcal infections in man and animals but not used because of its frequent and serious adverse effects (severe GI disturbances, allergy and blood dyscrasias).

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