In Vitro Activities of Five Oral Cephalosporins Against Aerobic Pathogenic Bacteria

The in vitro inhibitory activities of cefaclor and cefatrizine, two new orally absorbed cephalosporin antibiotics, against 44 isolates of anaerobic pathogenic bacteria were measured using the agar dilution procedure of the World Health OrganizationInternational Collaborative Study. Tests also were performed with cephalexin, cephaloglycin, and cephadrine, as well as with the parenteral cephamycin antibiotic cefoxitin. Cefoxitin was the most active antibiotic and inhibited the majority of isolates at a concentration of '4 pg/ml. None of the oral cephalosporins was clearly superior against all of the anaerobic isolates; only cephadrine and cefatrizine appeared to have any potential clinical value. Cefaclor (3-chloro-7-D-[2-phenyl-glycemanido]-3cepham-4-carboxylic acid) is a semisynthetic broad-spectrum cephalosporin antibiotic active against both gram-negative and gram-positive bacteria [1]. Metabolic studies in animals have shown that this drug is readily absorbed intact from the gastrointestinal tract [2]. Cefatrizine (7-[D-a,-amino-a- (hydroxylphenyl)acetamido]-3- (1 H,2,3-triazol-5-yl) thio]methyl]-3-cephem-4-carboxylic acid) is another semisynthetic cephalosporin with a similar spectrum of activity and also is absorbed from the gastrointestinal tract of rodents [3, 4]. The purpose of this study was to compare the in vitro activities of these two new orally absorbed cephalosporins with those of other orally absorbed cephalosporins against clinical isolates of anaerobic pathogenic bacteria. The other oral cephalosporins studied, now in clinical use, included cephalexin, cephaloglycin, and cephadrine. Because of its previously demonstrated activity against certain anaerobes [5], cefoxitin, a parenteral cephamycin antibiotic, was included for comparison.