Methicillin Sodium

- Overview
  - Methicillin Sodium is a narrow-spectrum β-lactam antibiotic belonging to the penicillin family and is a semi-synthetic derivative of penicillin. It was manufactured in the late 1950s. It is commonly used as a selective agent in pathogen isolation media, and in antimicrobial susceptibility testing. Methicillin Sodium is freely soluble in water.
    
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    Background
    
    β-lactams interfere with penicillin binding protein (PBP) 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 β-lactams is commonly due to cells containing plasmid encoded β-lactamases. Methicillin is mostly resistant to β-lactamases.
- Properties
  - CAS Number
    
    132-92-3
    
    Molecular Formula
    
    C17H19N2NaO6S
    
    Molecular Weight
    
    402.40
    
    Appearance
    
    White or almost white powder
    
    Solubility
    
    Acetone: 0.35 mg/mLEthanol: 40 mg/mLWater: Freely soluble
    
    Other Properties
    
    Source: Semi-synthetic
    Water Content (Karl Fischer): ≤10.0%
    Assay: ≥90.0%
    Melting Point: 196-197°C (dec.)
    Optical Rotation: +225°
    
    Storage
    
    -20°C
    
    * For research use only
- Applications
  - Application Description
    
    Spectrum: Methicillin targets primarily the cell wall of Gram-positive organisms especially Staphylococcus aureus.
    
    Microbiology Applications: Because of its widespread resistance among medically significant microbes, Methicillin may be used as a selective agent in pathogen isolation media to inhibit insignificant microbial background growth. Methicillin Sodium is commonly used in clinical in vitro microbiological antimicrobial susceptibility tests (panels, discs, and MIC strips) against Gram-positive microbial isolates. Methicillin is particularly used to test MRSA (Methicillin-resistant Staphylococcus aureus). Medical microbiologists use AST results to recommend antibiotic treatment options. Representative MIC values include:
    Staphylococcus aureus 0.5 µg/mL - 32 µg/mL