Biochem/physiol Actions Cloxacillin interferes with the last stage of bacterial cell wall synthesis by binding to penicillin-binding proteins. This inhibits the necessary cross-linking and leads to autolysis of the bacteria by autolysins. Application Cloxacillin is a semisynthetic antibiotic in the same class as penicillin. Cloxacillin is used against staphylococci that produce β-lactamase. It is used to study the role of pH in antibiotic effectiveness1 and how oxgall, acid, and hydrogen peroxide stress effects the susceptibility of Bifidobacteria2.