Fourteen antineoplastic agents were examined for in vitro antibacterial activity against 101 aerobic and anaerobic bacterial isolates representing indigenous human microflora and selected opportunistic pathogens. Only 5-fluorouracil, mitomycin, and etoposide demonstrated inhibitory effects at achievable plasma concentrations, while the remaining drugs lacked appreciable antibacterial activities.

The in vitro activities of moxalactam (LY127935 [6059S]) and cefotaxime were compared with those of cefoxitin, cefamandole, cefuroxime, carbenicillin, and penicillin by agar dilution susceptibility testing of a variety of anaerobic bacteria. Moxalactam proved to be the most active agent tested against Bacteroides fragilis and other species of the B. fragilis group. Moxalactam and cefotaxime showed activity similar to the other drugs against the remaining species of Bacteroides, Fusobacterium, Actinomyces, Propionibacterium, and Veillonella. Penicillin was the most effective drug tested against most species of Clostridium, the anaerobic gram-positive cocci, and Eubacterium lentum.

The in vitro activities of two new beta-lactam antibiotics, moxalactam disodium (LY 127935) and cefotaxime (HR-756), were compared with cefoxitin, cefamandole, cefuroxime, cephalothin, and, in some instances, carbenicillin, gentamicin, and amikacin against aerobic gram-negative bacilli. Test isolates included normally cephalosporin-resistant members of the Enterobacteriaceae and Pseudomonas spp. and a variety of nonfermentative or oxidase-positive bacteria. Both moxalactam and cefotaxime demonstrated impressive in vitro activities against both groups of microorganisms. The two new drugs were clearly more active than any of the other beta-lactam antibiotics against species of Escherichia, Citrobacter, Enterobacter, Klebsiella, Proteus, Providencia, Pseudomonas, and Serratia. An additive or synergistic effect could also be demonstrated with the majority of Pseudomonas and Serratia isolates when either moxalactam or defotaxime was combined with amikacin.

The susceptibilities of 159 clinical isolates of glucose nonfermentative gramnegative bacilli were determined for eight new monobactam or P-lactam antibiotics. Imipemide (N-formimidoyl thienamycin) was effective against the largest number of species, although not against Pseudomonas maltophilia. Cefoperazone and ceftazidime, but not cefsulodin, were active against infrequently isolated Pseudomonas species. Aztreonam, moxalactam, cefotaxime, and ceftizoxime demonstrated selective activity against several species, including certain aminoglycoside-resistant isolates.Members of the family Enterobacteriaceae and Pseudomonas aeruginosa are common causes of nosocomial infections. A wide variety of other aerobic gram-negative bacilli which are collectively characterized as being incapable of fermenting glucose, nonfermenters, are also encountered and are often resistant to extendedspectrum penicillins, first-and second-generation cephalosporins, or aminoglycosides (2,4,7,12). Newer-generation cephalosporins and related antibiotics containing a ,-lactam nucleus are highly active against many members of the Enterobacteriaceae and certain strains of P. aeruginosa (3,4,5,8). However, the activity of these newer agents against infrequently isolated nonfermenters is less clear.In

The in vitro synergistic activity of aztreonam in combination with piperacillin, moxalactam, cefotaxime, cefoperazone, and amikacin was examined against multiply resistant isolates of the family Enterobacteriaceae accommodating a volume of 1 ml of Mueller-Hinton broth (Difco Laboratories) were utilized. Each test isolate was grown overnight on sheep blood agar; then an inoculum of 5 x 105 CFU/ml was prepared by suspending growth to a predetermined optical density. Viable cell counts were performed with each test to verify the actual inoculum density which'was later utilized for MBC determinations. The cuvettes were immediately placed in an MS-2 analysis module and incubated at 35.5°C for 16 h with constant agitation. Optical density-versus-time plots were programmatically derived by the MS-2 system for each bacterial strain and antibiotic. The MIC was defined as the lowest concentration of drug which yielded consistent growth inhibition during the test period as evidenced by review of the kinetic plots. MBCs were determined at the conclusion of the incubation period by removing two 0.1-ml samples from each cuvette well demonstrating growth inhibition and spreading the samples over the entire surface of duplicate Trypticase soy agar (BBL Microbiology Systems) plates. Resultant colonies were counted after 18 to 20 h of incubation at 35°C. The MBC was defined as the lowest concentration of antibiotic resulting in a 23-log decrease in the number of viable organisms (99.9% kill) based on the previously determined inoculum density for each test.To determine possible synergistic effects, the separate MICs for each drug tested separately were combined in MS-2 research cuvettes as follows: