The mechanism of action of cephalosporin is:: (A) Interferes with cell wall synthesis, (B) Inhibition ol DNA gyrase, (C) Inhibition of protein synthesis, (D) Inhibition of DMA polymerase
Answer is A. Ans: A (Interferes with cell wall synthesis) Ref: Goodman & Gilmans The Pharmacological Basis of Therapeutics, 12th ed, 2011. Pg 1479, 1493: Basic and Clinical Pharmacology by Katzung, 2012, 12th ed, Pg 792Explanation:Cephalosporin inhibits bacterial cell wall synthesis.Its mechanism of action is similar to penicillin as both are beta lactams.Bacterial ceil wall plays a major role in the growth and development of bacteria.Peptidoglycan. a component of bacterial cell wall owing to its cross-linked structure offers strength to the cell wall.Peptidoglycan is composed of N-acetyl- glucosamine and N-acetylmuramic acid with cross-linking.A five amino acid peptide known as pentapeptide is linked to N-acetylmuramic acid and this peptide terminates as D-alanyl-D- alanine.Penicillin Binding Protein (PBP) removes terminal alanine from D-alanyl -D-alanine and forms cross link with the adjacent peptide, thus enhancing cell wall rigidity.Beta lactam antibiotics are structurally similar to D-alanyl -D-alanine, and hence covalently bind to PBP, resulting in inhibition of transpeptidation reaction w hich is essential for the removal of D-alanine from D-alanyl-D- alanine.As peptidoglycan synthesis is inhibited by cephalosporins as any other beta lactams, the bacterial cell dies. However cell death is maximum when the cells are actively growing and synthesizing cell wall.