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The antimicrobial activity of a new oxy-beta-lactam antibiotic LY 127935 against 1066 strains of gram-negative and gram-positive bacterial was evaluated in comparison to cephalothin. The antibiotic has a very wide spectrum and is exceptionally active, in particular against gram-negative rods. It is also active against multiresistant problem strains found in intensive care units (Enterobacter cloacae, Serratia marcescens, indole-positive Proteus), and proved to be quite effective against Pseudomonas aeruginosa. Although LY 127935 is effective against Staphylococcus aureus, cephalothin is superior. Its use is not indicated against Streptococcus faecalis.

The susceptibility of 115 Bacteroidaceae strains to LY 127935 was determined by broth dilution, agar dilution and agar diffusion tests. Simultaneously, the strains were tested for degradation of the oxa-beta-lactam. Only five strains (3 Bacteroides fragilis and 3 Bacteroides oralis/Bacteroides bivius) partially degraded LY 127935. No major discrepancies between the results of the agar dilution and broth dilution tests were observed. According to the results obtained by the agar dilution method, 50 strains of B. fragilus were inhibited by concentrations of less than or equal to 8 microgram oxa-beta-lactam per ml. Members of the Bacteroides melaninogenicus group of organisms had agar dilution MICs of less than or equal to 0.5 microgram LY 127935 per ml and Fusobacterium/Sphaerophorus species were inhibited by less than or equal to 64 microgram/ml. Strains of Bacteroides thetaiotaomicron, B. oralis/B. bivius and Bacteroides spp. were less susceptible. Due to the narrow range of MICs observed with B. fragilis strains, no regression line could be computed for the relationship between MIC and zone size.

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.

Ceftriaxon (Ro 13-9904) is a new cephalosporin, whose structure resembles cefotaxime. This study compares the minimal inhibitory concentrations (MIC-s) of Ceftriaxon, cefoperazone, cefotaxime, lamoxactam and gentamicin against 622 isolates of various Enterobacteriaceae, non-fermenters and Aeromonas hydrophila. Furthermore the minimal bactericidal concentrations (MBC-s) were determined for some organism; additionally destruction of beta-lactamantibiotics in the presence of beta-lactamases was studied by a bioassay technique. The in vitro activity of Ceftriaxon against gramnegative bacteria was found very similar to that of cefotaxime. The susceptibility of Enterobacter sp. to the three cephalosporines was exceeded by lamoxactam while cefoperazone was the most active beta-lactam-antibiotic against Pseudomonas. Lactamases, which inactivated cefotaxime also destroyed Ceftriaxon in a greater extend. No hydrolysis of lamoxactam and cefoperazone occurred by nearly all bacterial extracts tested.