• Methicillin sodium packaged and labeled.

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SKU: M029

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Methicillin Sodium is a narrow spectrum β-lactam antibiotic in the penicillin family and is commonly used as a selective agent in pathogen isolation media, and in antimicrobial susceptibility testing. It is soluble in aqueous solution (0.3 mg/mL).

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    Mechanism of Action

    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.

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    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

    For a representative list of Methicillin MIC values, click here.





    White or almost white powder



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    Melting Point

    196-197°C (dec.)

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    Joshi SG et al (2010)  Control of methicillin-resistant Staphylococcus aureus in planktonic form and biofilms: A biocidal efficacy study of nonthermal dielectric-barrier discharge plasma. A. J. Infect. Cont. 38(4):293-301

    Kehrenberg C, Cuny C, Strommenger B, Schwarz S, Witte W (2009)  Methicillin-resistant and -susceptible Staphylococcus aureus strains of clonal llineages ST398 and ST9 from swine carry the multidrug resistance gene cfr. Antimicrob. Agents Chemother. 2009 Feb;53(2):779-81. PMID 19047652

    Pitout JD, Sanders CC, Sanders WE (1997)  Antimicrobial resistance with focus on beta-lactam resistance in gram-negative bacilli. Am J Med 103:51

    Sjöström JE, Löfdahl S, and Philipson L (1975)  Transformation reveals a chromosomal locus of the gene(s) for methicillin resistance in Staphylococcus aureus. J. Bacteriol. 123 (3):905-915

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