Mechanism of action
Bactericidal and act by interfering with bacterial cell wall synthesis.
Ampicillin exerts bactericidal action on both gm+ve and gm-ve organisms. Its spectrum includes gm+ve organisms eg, S pneumoniae and other Streptococci, L monocytogenes and gm-ve bacteria eg, M catarrhalis, N gonorrhoea, N meningitidis, E coli, P mirabilis, Salmonella, Shigella, and H influenzae. Ampicillin exerts its action by inhibiting the synthesis of bacterial cell wall.
Cloxacillin is a penicillinase-resistant penicillin. It is active against gm+ve organisms including penicillinase-producing strains of Staphylococci. Cloxacillin is highly active against Staph aureus, Strep pyogenes, Strep viridans and Strep pneumoniae. It is also active against penicillinase-producing gonococci and against N meningitidis and H influenzae. Other gm-ve organisms are resistant to cloxacillin as are also methicillin-resistant strains of Staphylococci.