Cefixime Trihydrate

- Overview
  - Cefixime Trihydrate is a broad-spectrum third generation cephalosporin targeting a wide range of Gram-positive and Gram-negative organisms. Cefixime Trihydrate is active against pathogens responsible for respiratory tract infections such as Haemophilus influenzae and Moraxella catarrhalis.
    
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    Background
    
    Like β-lactams, cephalosporins interfere with PBP (penicillin binding protein) activity involved in the final phase of peptidoglycan synthesis. PBP’s are enzymes which catalyze a pentaglycine crosslink between alanine and lysine residues providing additional strength to the cell wall. Without a pentaglycine crosslink, the integrity of the cell wall is severely compromised and ultimately leads to cell lysis and death. Resistance to cephalosporins is commonly due to cells containing plasmid encoded β-lactamases. Cefixime however, is resistant to many β-lactamases encoded by β-lactam resistant strains.
- Properties
  - CAS Number
    
    125110-14-7 (trihydrate); 79350-37-1 (anhydrous)
    
    Molecular Formula
    
    C16H15N5O7S2 • 3 H2O
    
    Molecular Weight
    
    507.50
    
    Appearance
    
    Light yellow crystalline powder
    
    Other Properties
    
    Source: Synthetic
    Water Content (Karl Fischer): 9.0-12.0%
    PH: 2.6-4.1
    Assay: (On Dried Basis): 950-1030 µg/mg
    Optical Rotation: -75° to -88°
    
    Storage
    
    -20°C
    
    * For research use only
- Applications
  - Application Description
    
    Spectrum: Cefixime Trihydrate is active against Gram-positive and Gram-negative bacteria
    
    Microbiology Applications: Cefixime Trihydrate is commonly used in clinical in vitro microbiological antimicrobial susceptibility tests (panels, discs, and MIC strips) against Gram-positive and Gram-negative microbial isolates. Medical microbiologists use AST results to recommend antibiotic treatment options. Representative MIC values include:
    Haemophilus influenzae 0.008 µg/mL – 2 µg/mL
    Moraxella catarrhalis 0.06 µg/mL – 0.5 µg/mL
    Media Supplements
    Cefixime can be used as a selective agent in several types of isolation media:
    Sorbitol Macconkey Agar - Cefixime-Tellurite Supplement
    mTSB - VCC Selective Supplement
    CR-SMAC - Cefixime Supplement
    
    Eukaryotic Cell Culture Applications: Flavonoids from plants were able to alter the transport of Cefixime via PEPT1 in Caco-2 cells. Of the 33 flavonoids tested, quercetin, genistein, naringin, diosmin, acacetin, and chrysin increased Cefixime uptake by up to 60% via activating apical Na+/H+ exchange (Wenzel et al, 2001).
    Uptate of the anionic B-lactam Cefixime was studied using human Caco-2 human intestinal epitherlial cell line expressing intestinal peptide transporter (PEPT1). Researchers found that alterations of Ca2+ by Ca2+ channel blockers affect the pH of regulatory systems like apical Na+ and H+ exchange and alter the H+ gradient which is the driving force for uptake into epithelial cells. For example, at a surface pH of ≥ 6.25, the predominant fraction of Cefixime is charged, and thus shows only very low levels of interaction with PEPT1. The addition of the calcium blocker Nifedipine reduces the intracellular acidification induced by the influx of Cefixime and maintained a higher electrochemical proton gradient across the apical plasma membrane, allowing higher transport rates (Wenzel et al, 2002).