Ceftazidime: Broad-Spectrum Third-Generation Cephalosporin for Resistant Gram-Negative Infections

Executive Summary: Ceftazidime is a β-lactamase-resistant, third-generation cephalosporin with high efficacy against Gram-negative bacteria, notably Pseudomonas aeruginosa (APExBIO product page). It remains among the most active cephalosporins for P. aeruginosa infections, though it is less potent against Staphylococcus aureus than earlier generations. The molecular weight is 546.58 g/mol (solid form), and solubility is ≥21.25 mg/mL in DMSO. Ceftazidime inhibits bacterial cell wall synthesis, causing bactericidal effects; it also demonstrates stable resistance to hydrolysis by extended-spectrum β-lactamases, making it suitable for multidrug-resistant research contexts (Chen et al., 2025). Recommended storage is at -20°C to preserve activity.

Biological Rationale

Ceftazidime is a third-generation cephalosporin, classified as a β-lactam antibiotic. It exhibits a broad spectrum of in vitro activity, targeting both Gram-positive and Gram-negative aerobic bacteria. Its most notable efficacy is against Pseudomonas aeruginosa and other Pseudomonas species, including P. cepacia, P. alcaligenes, and P. putida (Related Article). Ceftazidime is highly resistant to hydrolysis by β-lactamases, which are enzymes that confer antibiotic resistance in many clinical isolates of Enterobacteriaceae. This resistance enhances its value in research on multidrug-resistant pathogens such as carbapenem-resistant Enterobacter cloacae (CREC) (Chen et al., 2025). The global rise in β-lactamase-producing strains has elevated the clinical and investigative importance of ceftazidime in both hospital and laboratory settings.

Mechanism of Action of Ceftazidime

Ceftazidime exerts its antibacterial effect by binding to penicillin-binding proteins (PBPs) within the bacterial cell wall. This binding inhibits the final transpeptidation step of peptidoglycan synthesis, disrupting cell wall integrity. The result is osmotic instability and bacterial cell lysis. The compound’s β-lactam ring is structurally resistant to most β-lactamases, conferring its stability even in the presence of many resistance factors (APExBIO). Ceftazidime is thus particularly effective against Gram-negative bacteria that express β-lactamases, including extended-spectrum β-lactamase (ESBL) and some carbapenemase producers.

Evidence & Benchmarks

• Ceftazidime demonstrates high activity in vitro against Pseudomonas aeruginosa, with minimum inhibitory concentrations (MICs) typically ≤8 μg/mL under standard broth microdilution protocols (APExBIO).
• Resistance rates to ceftazidime in carbapenemase-encoding gene (CEG)-positive Enterobacter cloacae isolates are significantly higher than CEG-negative isolates, reflecting the challenge in treating these infections (Chen et al., 2025).
• In clinical research, ceftazidime is dosed at 3–6 g/day, divided into 2–4 intravenous infusions, for severe pneumonia and bronchitis caused by susceptible Gram-negative organisms (APExBIO).
• Ceftazidime stock solutions remain stable at concentrations ≥21.25 mg/mL in DMSO when stored below -20°C for up to several months (APExBIO).
• Its efficacy against Staphylococcus aureus is lower compared to first- or second-generation cephalosporins, highlighting its Gram-negative focus (Related Article).

Applications, Limits & Misconceptions

Ceftazidime is widely used in microbiology research, clinical trials, and therapeutic settings to treat infections caused by susceptible Gram-negative bacteria, including those resistant to other β-lactams. Its robust activity against Pseudomonas aeruginosa makes it a critical option in nosocomial pneumonia and bronchitis studies. APExBIO supplies ceftazidime (SKU: B3539) in solid form, ensuring purity and batch-to-batch consistency (Ceftazidime product page). For a comprehensive review of ceftazidime’s antibacterial spectrum and resistance profile, see the related article, which this dossier updates with new data from recent carbapenem-resistant Enterobacteriaceae studies (Interlinked Article).

Common Pitfalls or Misconceptions

• Ceftazidime is not effective against most carbapenemase-producing Enterobacteriaceae, as resistance rates are elevated in these strains (Chen et al., 2025).
• The compound displays low activity against Gram-positive bacteria, especially Staphylococcus aureus, compared to earlier cephalosporins (Related Article).
• Ceftazidime is insoluble in ethanol and water, requiring dissolution in DMSO for experimental use (APExBIO).
• Stock solutions lose potency if stored above -20°C or kept for extended periods at room temperature.
• It should not be used as monotherapy in infections caused by proven or suspected carbapenemase-producing organisms.

Workflow Integration & Parameters

Ceftazidime (APExBIO B3539) is supplied as a solid. It is soluble at ≥21.25 mg/mL in DMSO, but insoluble in water and ethanol. Stock solutions should be prepared fresh or stored below -20°C to maintain potency. In in vitro studies, concentrations ranging from 0.25 μg/mL to 256 μg/mL are commonly used for MIC testing. For in vivo or cell culture studies, dosing should mirror clinical pharmacokinetics, with typical regimens involving divided daily doses totaling 3–6 g for human research protocols. Always monitor for degradation, especially if solutions are stored at higher temperatures or for prolonged periods.

Conclusion & Outlook

Ceftazidime remains a cornerstone cephalosporin for research on Gram-negative, β-lactamase-producing pathogens, particularly Pseudomonas aeruginosa. Its resistance to β-lactamase hydrolysis extends its utility in multidrug-resistant infection studies and clinical protocols. However, emerging carbapenemase-mediated resistance necessitates ongoing surveillance and combination strategies. This dossier updates and clarifies earlier overviews, offering precise solubility, stability, and resistance data for workflow optimization. For the latest research-grade supplies and technical documentation, refer to the APExBIO Ceftazidime product page.