Cloxacillin-13C4 is intended for use as an internal standard for the quantification of cloxacillin by GC- or LC-MS. Cloxacillin is a semisynthetic β-lactamase inhibitor.1 It binds to and inactivates penicillin-binding proteins that cross-link peptidoglycans, which are structural components of bacterial cell walls. In vitro, cloxacillin (0.50 μg/ml) completely inhibits B. megaterium growth.2 Cloxacillin inhibits recombinant type Ib penicillinase, P. vulgaris cephalosporinase, and C. freundii cephalosporinase (Kis = 15, 0.27, and 0.027 μM, respectively) as well as S. aureus and S. epidermidis growth (MIC = 0.2 μg/ml for both).3,4 Formulations containing cloxacillin have been used to treat infections caused by methicillin-sensitive staphylococci.1
|1. Bru, J.P., and Garraffo, R. Role of intravenous cloxacillin for inpatient infections. Med. Mal. Infect. 42(6), 241-246 (2012).|2. Wickus, G.G., and Strominger, J.L. Penicillin-sensitive transpeptidation during peptidoglycan biosynthesis in cell-free preparations from Bacillus megaterium. II. Effect of penicillins and cephalosporins on bacterial growth and in vitro transpeptidation. J. Biol. Chem. 247(17), 5307-5311 (1972).|3. Yamaguchi, A., Adachi, A., Hirata, T., et al. Conversion of cloxacillin into a progressive inhibitor of beta-lactamases by sulfonation and its activity against various types of these enzymes. J. Antibiot. (Tokyo) 38(1), 83-93 (1985).|4. Sabath, L.D., Garner, C., Wilcox, C., et al. Susceptibility of Staphylococcus aureus and Staphylococcus epidermidis to 65 antibiotics. Antimicrob. Agents Chemother. 9(6), 962-969 (1976).