The in-vitro activity of cefpodoxime: a comparison with other oral cephalosporins

Abstract

The in-vitro activity of cefpodoxime was studied in 529 clinical isolates and compared with the activity of other oral β-lactams. Amongst the Enterobacteriaceae cefpodoxime was very active (MIC₉₀≤1 mg/l—other than genera commonly possessing chromosomal β-lactamases). Against these strains cefpodoxime was comparable in activity to cefixime and about eight-fold more active than cefuroxime and 8–16-fold more active than cefaclor and cephalexin. Staphylococcus aureus strains were moderately susceptible (MIC₉₀ 4mg/l) to cefpodoxime in comparison with cefixime (16 mg/l). The respiratory pathogens, Haemophilus influenzae, Streptococcus pneumoniae and Branhamella catarrhalis were susceptible to ≤ 0·5 mg/l cefpodoxime. An increase in inoculum from 10⁴ to 10⁶ cfu had little effect upon activity. Studies in β-lactamase hydrolysis of cefpodoxime showed it to be stable to TEM-1, SHV-1 and BRO-1 enzymes but with high affinity for the P99 enzyme. The primary target of cefpodoxime is PBP3 (I₅₀ 1 mg/l) in Escherichia coli Kl2. The protein binding of the agent to human serum was 14·3–18·3% at 1 and 5 mg/l respectively.