Cloxacillin is a β-lactam antibiotic and a derivative of oxacillin (Item No.
23954).
1 It is active against clinical isolates of the Gram-positive bacteria
S. aureus and
S. epidermidis (MICs = 0.004-0.4 and 0.1-0.8 μg/ml, respectively) but not 34 Gram-negative bacteria (MICs = >128 μg/ml for all).
1,2 Cloxacillin binds to
S. aureus penicillin-binding protein 1 (PBP1), PBP2, PBP3, and PBP4 (IC
50s = 0.04, 0.12, 0.21, and 2.5 μg/ml, respectively).
3 It also binds to recombinant type Ib penicillinase, as well as
P. vulgaris and
C. freundii cephalosporinase (K
is = 15, 0.27, and 0.027 μM, respectively).
4 Cloxacillin decreases the number of staphylococci in the mammary gland in a mouse model of acute, but not chronic, mastitis induced by
Staphylococcus infection.
5