Antimicrobial activities of six new oral cephem antibiotics

Six newly developed oral cephem antibiotics, which included 5 with an aminothiazolyl side chain, viz., cefixime, cefotiam hexetil, cefpodoxime proxetil, cefteram pivoxil, ceftibuten, and one with a conventional side chain design, BMY 28100, were tested for their antimicrobial activities. Three traditional oral beta-lactam antibiotics, ampicillin, cephalexin, and cefaclor, were used as reference antibiotics. The 5 aminothiazolyl cephems were more active than the reference drugs against clinical isolates of Escherichia coli, Klebsiella pneumoniae and Haemophilus influenzae. All 6 new drugs showed poor activity against clinical isolates of Enterobacter cloacae, Pseudomonas aeruginosa, and enterococci. They were better than cephalexin and cefaclor, but slightly poorer than or the same as ampicillin in activities against Streptococcus pyogenes and Streptococcus pneumoniae. Cefotiam hexetil, BMY 28100, and cefpodoxime proxetil were also more active than cephalexin against Staphylococcus aureus. Although the 6 tested new oral cephems demonstrated little difference in their activities against different bacteria, they all showed greater antimicrobial activity than the traditional oral antibiotics now in clinical use.