In vitro antimicrobial activity of 6315-S (Flomoxef) and its therapeutic efficacy in lower respiratory infections

In vitro antimicrobial activity of 6315-S (Flomoxef), a new oxacephem for parenteral use, was examined by a broth dilution method using the Dynatech MIC 2000 system, and its therapeutic effects in lower respiratory infections were evaluated. The minimum inhibitory concentrations (MIC‘s) and minimum bactericidal concentrations (MBC‘s) of 6315-S, latamoxef (LMOX=moxalactam), ceftizoxime (CZX), cefmenoxime (CMX), cefmetazole (CMZ), cefazolin (CEZ) and ampicillin (ABPC) against the following 239 clinical isolates were determined: 20 strains each of S. aureus, S. epidermidis, E. coli, K. pneumoniae, E. cloacae, S. marcescens and P. aeruginosa, 25 strains of S. pneumoniae, 9 strains of S. pyogenes and 65 strains of H. influenzae. From the determination of MIC’s and MBC’s, it was found that 6315-S was more active against S. aureus than any other antibiotic, and as active as ABPC against H. influenzae. 6315-S was somewhat less active against S. epidermidis and streptococci than CEZ and ABPC, respectively. Compared with LMOX, 6315-S was more active against E. coli and K. pneumoniae, but less so against E. cloacae and S. marcescens. 6315—S was also less. active against P. aeruginosa with MIC’s above 200 μg/ml against all the strains tested. MBC values of 6315-S against a wide variety of pathogens were found to be very close to MIC’s. A daily dose of lg to 4 of 6315-S was given by drip infusion to 21 patients: 17 with pneumonia and 2 each with lung abscess and infection in association with bronchiectasis. Clinical effects were excellent in 2 patients, good in 11, fair in 1 and poor in 5. One patient with Mycoplasma pneumoniae infection and one who received 6315-S only twice because of adverse side effects were excluded from clinical evaluation. Nineteen strains were identified as causative organisms. However, in 4 strains, further bacteriological data were not available for evaluation. Fourteen of the remaining 15 strains were eradicated by 6315~S; only one strain persisted. Drug exanthema was observed in one patient, and elevation in SGOT and SGPT values was observed in five. These adverse reactions disappeared after completion of the therapy. From the above results, we conclude that 6315-S is a most useful antibiotic for the treatment of lower respiratory infections.