[Moxalactam and cefotaxime--two new beta-lactam antibiotics compared with three well-known cephalosporins]

Abstract

This study compares the minimum inhibitory concentrations of moxalactam and cefotaxime, two beta-lactam-antibiotics, with those of cefoxitin, cefuroxime, and cefazolin for 523 gram-positive and -negative strains. Moxalactam and cefotaxime inhibit nearly all clinically important Enterobacteriaceae at concentrations less than 0.05 microgram/ml. Cefoxitin, cefuroxime, and cefazolin suppress bacterial growth at about 5--10 times higher concentrations. All strains of Pseudomonas are normally resistant to those three established cephalosporins, but about 60% are susceptible to 32 micrograms/ml of cefotaxime and moxalactam, a concentration which falls below achievable serum levels however does not exhibit any therapeutical effect. Against Staphylococcus aureus cefazolin is the most effective of all antibiotics tested (MIC 0.125--1 microgram/ml), cefotaxime appears to be somewhat less active (MIC 2--4 micrograms/ml), and a minimum of 8 micrograms/ml of moxalactam is needed to prevent bacterial growth. Streptococcus faecalis seems to be resistant to 128 micrograms/ml of moxalactam whereas the effect of cefotaxime is quite different. After transfers of Enterobacteriaceae on media containing cefotaxime or moxalactam a striking decrease of susceptibility sometimes occurs.