Cefpodoxime: comparable evaluation with other orally available cephalosporins. With a note on the role of beta-lactamases.

The antibacterial activity of cefpodoxime, a new orally active methoxy-imino cephalosporin was evaluated in 470 recent isolates of gram-positive cocci and gram-negative rods from clinical specimens and compared to that of other orally active beta-lactam compounds. Cefpodoxime was highly active against ampicillin-resistant enterobacteria producing the plasmid-mediated TEM-1, TEM-2 or OXA-1 enzymes, as was the case for the other newer compounds. However, it was poorly active against cefuroxime-resistant (MIC greater than or equal to 16 mg/l) E. coli isolates, thus resembling cefetamet and cefixime. It was inactive against isolates exhibiting a production of large amounts of class I beta-lactamase, as was the case with all other compounds studied. Cefpodoxime was highly active against beta-hemolytic streptococci and against Haemophilus influenzae, resembling the related agents. Moreover, its activity against Staphylococcus aureus was comparable to that of cefotaxime and exceeded that of cefetamet and cefixime. Cefpodoxime and the other methoxyimino cephalosporins exhibited a poor affinity to the plasmid-mediated TEM-2 and OXA-1 enzymes. The hydrolysis of cefpodoxime by class I beta-lactamases was barely detectable, whereas it served as a moderate substrate for the enzyme from Klebsiella oxytoca 3951. Cefpodoxime, cefetamet and cefixime were slowly inactivated by the enzyme from Proteus vulgaris 4917 (an enzyme with cefuroximase activity) and much poorer substrates than cefotaxime.