Temocillin compared to ampicillin against Haemophilus influenzae and with other penicillins against intestinal aerobic Gram-negative rods

Abstract

Temocillin is a recently developed penicillin with a methoxy group in the 6-alpha position. We studied the in-vitro antimicrobial activity against Haemophilus influenzae and Enterobacteriaceae and the extent of stability to hydrolysis by β-lactamases produced by Gram-negative bacteria. MICs for 76 strains of H. influenzae were compared with MICs of ampicillin. MICs for 130 strains of Enterobacteriaceae (including 65 carbenicillin-resistant strains) and for 27 other Gram-negative rods were compared with carbenicillin, mezlocillin and piperacillin. Thirty-five out of 38 β-actamase-producing H. influenzae were inhibited by 2 mg/l of temocillin and 90% of carbenicillin-resistant Enterobacteriaceae were inhibited by 8 mg/1 of temocillin. Only one strain each of Serratia marcescens and Proteus mirabilis was found to be resistant. No significant enhancement by clavulanic acid on temocillin could be observed in 20 strains of Gram-negative rods producing β-lactamases. Using bioassay methods temocillin was shown to be highly resistant to all β-lactamase extracts tested with the exception of those from Flavobacterium sp.