Methicillin (USAN) or meticillin (INN, BAN) is a narrow spectrum beta-lactam antibiotic. It was previously used to treat infections caused by susceptible Gram-positive bacteria, particularly beta-lactamase-producing organisms such as Staphylococcus aureus that would otherwise be resistant to most penicillins, but is no longer clinically used. Its role in therapy has been largely replaced by flucloxacillin and dicloxacillin, however the term methicillin-resistant Staphylococcus aureus (MRSA) continues to be used to describe Staphylococcus aureus strains resistant to all penicillins. CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences and alloys. ... The Anatomical Therapeutic Chemical Classification System is used for the classification of drugs. ... PubChem is a database of chemical molecules . ... DrugBank is a database available at the University of Alberta that provides information about thousands of products. ... A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... In pharmacology, bioavailability is used to describe the fraction of an administered dose of medication that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. ... The elimination half-life of a drug (or any xenobiotic agent) refers to the timecourse necessary for the quantity of the xenobiotic agent in the body (or plasma concentration) to be reduced to half of its original level through various elimination processes. ... Excretion is the process of eliminating waste products of metabolism and other materials that are of no use. ... The pregnancy category of a pharmaceutical agent is an assessment of the risk of fetal injury due to the pharmaceutical, if it is used as directed by the mother. ... The regulation of therapeutic goods, that is drugs and therapeutic devices, varies by jurisdiction. ... An intravenous drip in a hospital Intravenous therapy or IV therapy is the administration of liquid substances directly into a vein. ... A United States Adopted Name (USAN) is the official non-proprietary or generic name given to a pharmaceutical substance, as defined in the United States Pharmacopeia (USP). ... An International Nonproprietary Name (INN) is the official non-proprietary or generic name given to a pharmaceutical substance, as designated by the World Health Organization. ... A British Approved Name (BAN) is the official non-proprietary or generic name given to a pharmaceutical substance, as defined in the British Pharmacopoeia (BP). ... A narrow-spectrum antibiotic is an antibiotic that is useful for a restricted group of microorganisms. ... β-lactam antibiotics are a broad class of antibiotics including penicillin derivatives, cephalosporins, monobactams, carbapenems and β-lactamase inhibitors; basically any antibiotic agent which contains a β-lactam nucleus in its molecular structure. ... An infection is the detrimental colonization of a host organism by a foreign species. ... Gram-positive bacteria are those that are stained dark blue or violet by gram staining, in contrast to gram-negative bacteria, which are not affected by the stain. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Beta-lactamase is a type of enzyme (EC 3. ... Binomial name Staphylococcus aureus Rosenbach 1884 Staphylococcus aureus, the most common cause of staph infections, is a spherical bacterium, frequently living on the skin or in the nose of a healthy person, that can cause a range of illnesses from minor skin infections (such as pimples, boils, and cellulitis) and... For the Japanese rock band, see Penicillin (band). ... Flucloxacillin (INN) or floxacillin (USAN) is a narrow spectrum beta-lactam antibiotic. ... Dicloxacillin (INN) is a narrow spectrum beta-lactam antibiotic. ... Electron micrograph of MRSA Methicillin-resistant Staphylococcus aureus (MRSA) (a. ... Binomial name Staphylococcus aureus Rosenbach 1884 Staphylococcus aureus, the most common cause of staph infections, is a spherical bacterium, frequently living on the skin or in the nose of a healthy person, that can cause a range of illnesses from minor skin infections (such as pimples, boils, and cellulitis) and... For the Japanese rock band, see Penicillin (band). ...

Mode of action

Main article: Beta-lactam antibiotic β-lactam antibiotics are a broad class of antibiotics including penicillin derivatives, cephalosporins, monobactams, carbapenems and β-lactamase inhibitors; basically any antibiotic agent which contains a β-lactam nucleus in its molecular structure. ...

Like other β-lactam antibiotics, methicillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell wall of Gram-positive bacteria. A cell wall is a fairly rigid layer surrounding a cell located outside of the plasma membrane (also known, in some cases, as the cell membrane) that provides additional support and protection. ... Peptidoglycan, also known as murein, is a substance that forms a homogeneous layer lying outside the plasma membrane in bacteria. ... Gram-positive bacteria are those that are stained dark blue or violet by gram staining, in contrast to gram-negative bacteria, which are not affected by the stain. ...

Medicinal chemistry

Methicillin is insensitive to beta-lactamase (also known as penicillinase) enzymes secreted by many penicillin-resistant bacteria. The presence of the ortho-dimethoxyphenyl group directly attached to the side chain carbonyl group of the penicillin nucleus facilitates the β-lactamase resistance, since those enzymes are relatively intolerant of side-chain steric hindrance. Thus it is able to bind to penicillin binding proteins (PBPs) and inhibit peptidoglycan crosslinking, but is not bound by or inactivated by β-lactamases. Beta-lactamase is a type of enzyme (EC 3. ... The term Side chain can have different meanings depending on the context: In chemistry and biochemistry a side chain is a part of a molecule attached to a core structure. ... Steric effects are the interaction of molecules dictated by their shape and/or spatial relationships. ... Bacterial proteins that exhibit either transpeptidase or carboxypeptidase activity. ... Peptidoglycan, also known as murein, is a substance that forms a homogeneous layer lying outside the plasma membrane in bacteria. ...

Clinical use

Methicillin is not commonly used in clinical practice, but serves a purpose in the laboratory to determine antibiotic sensitivity in microbiological culture. Methicillin was previously used to treat infections caused by susceptible Gram-positive bacteria. It is unstable in the presence of gastric acid, with a degradation half-life of 5 minutes at pH 2, so it must be administered by injection. (Mitscher, 2002) Michael Faraday, 19th century physicist and chemist, in his lab. ... A microbiological culture is a way to determine the cause of infectious disease by letting the agent multiply (reproduce) in predetermined media. ... Gram-positive bacteria are those that are stained dark blue or violet by gram staining, in contrast to gram-negative bacteria, which are not affected by the stain. ... Gastric acid is, together with several enzymes and the intrinsic factor, one of the main secretions of the stomach. ... An injection is a method of putting liquid into the body with a hollow needle and a syringe which is pierced through the skin long enough for the material to be forced into the body. ...

See also

• Beta-lactam antibiotic
• Flucloxacillin
• Methicillin-resistant Staphylococcus aureus

β-lactam antibiotics are a broad class of antibiotics including penicillin derivatives, cephalosporins, monobactams, carbapenems and β-lactamase inhibitors; basically any antibiotic agent which contains a β-lactam nucleus in its molecular structure. ... Flucloxacillin (INN) or floxacillin (USAN) is a narrow spectrum beta-lactam antibiotic. ... Electron micrograph of MRSA Methicillin-resistant Staphylococcus aureus (MRSA) (a. ...

References

• Mitscher LA. Antibiotics and antimicrobial agents. In: Williams DA, Lemke TL, editors. Foye's Principles of medicinal chemistry, 5th edition. Philadelphia: Lippincott Williams & Wilkins; 2002.