Cefpodoxime Spectrum of Activity
Cefpodoxime is a third-generation oral cephalosporin with broad-spectrum activity against both gram-positive and gram-negative bacteria, though it demonstrates particularly potent activity against gram-negative respiratory pathogens and Enterobacteriaceae. 1, 2
Gram-Negative Coverage
Cefpodoxime exhibits excellent activity against most clinically relevant gram-negative organisms:
Respiratory pathogens: Inhibits Haemophilus influenzae (including beta-lactamase-producing strains), Moraxella catarrhalis, and Neisseria species at concentrations ≤1 mg/L (MIC90 0.12-1 mg/L) 1, 3
Enterobacteriaceae: Demonstrates potent activity against Escherichia coli, Klebsiella spp., Proteus mirabilis, Proteus vulgaris, Providencia spp., Salmonella spp., and Serratia spp. with MIC90 values ≤1 mg/L 1, 4
Activity superior to older cephalosporins: Cefpodoxime's gram-negative coverage consistently exceeds that of cefuroxime and is comparable to cefixime for most Enterobacteriaceae 1, 5
Gram-Positive Coverage
While cefpodoxime has gram-positive activity, it is generally less impressive than its gram-negative spectrum:
Streptococci: Highly active against Streptococcus pneumoniae, group A/B/G streptococci, and Streptococcus pyogenes with MIC90 values <0.12-0.25 mg/L 1, 3
Staphylococci: Moderate activity against methicillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci (MIC50 1-4 mg/L), which is reasonable but not exceptional 4, 5
Advantage over cefixime: Unlike cefixime (which has poor staphylococcal activity with MICs >8 mg/L), cefpodoxime retains clinically useful activity against oxacillin-susceptible staphylococci 1, 4
Organisms Without Activity
- No activity against Pseudomonas spp., Acinetobacter spp., enterococci, or methicillin-resistant staphylococci 1, 4
Critical Limitations for Enterobacter Species
Do not use cefpodoxime empirically for suspected Enterobacter infections, particularly in hospital-acquired or healthcare-associated settings. 6
Enterobacter species produce inducible AmpC beta-lactamases that can lead to treatment failure even when initial susceptibility testing suggests sensitivity 6
Carbapenems remain the preferred agents for serious Enterobacter infections, especially in nosocomial settings 6
Avoid relying on initial susceptibility testing alone for Enterobacter, as inducible resistance mechanisms can emerge during therapy 6
Clinical Context
Cefpodoxime achieves tissue concentrations in tonsils (0.24 mg/kg), lung parenchyma (0.89 mg/kg), and bronchial mucosa (0.91 mg/kg) that far exceed the MICs for respiratory pathogens 2. This makes it particularly well-suited for community-acquired respiratory tract infections where gram-negative organisms like H. influenzae and M. catarrhalis are common pathogens, while maintaining adequate coverage of gram-positive S. pneumoniae and S. pyogenes 2, 3.