Forty-two isolates of Bacteroides fragilis were tested against five new cephalosporin antibiotics by two quantitative methods, microdilution and agar dilution. Results indicated satisfactory methodological agreement. Mean minimum inhibitory concentrations (MIC) of thienamycin, moxalactam, and ceftizoxime were significantly lower than with the other antibiotics tested.

Multiple morphotypes of Pseudomonas aeruginosa isolated from 50 respiratory specimens of cystic fibrosis patients were tested for correlation of broth microdilution susceptibility results of a mixed-morphotype inoculum with a predicted antibiogram of the individual isolates. The overall correlation was 96.0%, with only 1.6% very major or major errors.

The in vitro inhibitory activity of trimethoprim-sulfamethoxazole is inversely related to the amount of thymine and thymidine in the test medium; manufacturers must adequately control their media to avoid spurious antimicrobial susceptibility results. No differences were observed when commercial Mueller-Hinton broth and agar were compared with a semisynthetic broth medium by the use of microdil...

Florfenicol in vitro activities for a total of 756 bacterial isolates from respiratory tract infections of cattle and swine were comparatively investigated by the agar diffusion method and the microdilution broth method. Florfenicol showed high in vitro activity against Pasteurella multocida, Mannheimia haemolytica, Actinobacillus pleuropneumoniae, and Streptococcus suis, with all of the isolat...

MICs of 22 antimicrobial agents for 60 strains of three Aeromonas species were determined by a microdilution method. The newer cephalosporins such as moxalactam, cefotaxime, and cefoperazone, the aminoglycosides, and chloramphenicol, tetracycline, nitrofurantoin, and trimethoprim-sulfamethoxazole inhibited most of the strains studied. Within the genus, A. hydrophila was more resistant than eith...