|Systematic (IUPAC) name|
|Bioavailability||30–37% (oral, fosfomycin tromethamine); varies with food intake|
|Biological half-life||5.7 hours (mean)|
|Excretion||Renal and fecal, unchanged|
|CAS Registry Number||78964-85-9|
|Molecular mass||138.059 g/mol|
|Melting point||94 °C (201 °F)|
|(what is this?)|
Fosfomycin (also known as phosphomycin, phosphonomycin and the trade name Monurol and Monuril) is a broad-spectrum antibiotic produced by certain Streptomyces species, although it can now be made by chemical synthesis.
Fosfomycin (originally known as phosphonomycin) was discovered in a joint effort of Merck and Co. and Spain's Compañía Española de Penicilina y Antibióticos (Cepa). It was first isolated by screening broth cultures of Streptomyces fradiae isolated from soil samples for the ability to cause formation of spheroplasts by growing bacteria. The discovery was described in a series of papers published in 1969. Cepa began producing fosfomycin on an industrial scale in 1971 at its Aranjuez facility.
Fosfomycin is indicated in the treatment of urinary tract infections, where it is usually administered as a single oral megadose. Its use in combination with tobramycin to treat lung infections in patients with cystic fibrosis was also explored.
The drug is well tolerated and has a low incidence of harmful side-effects. However, development of bacterial resistance under therapy is a frequent occurrence and makes fosfomycin unsuitable for sustained therapy of severe infections. It is not recommended for children and those over 75 years old.
Mechanism of action
Fosfomycin is bactericidal and inhibits bacterial cell wall biogenesis by inactivating the enzyme UDP-N-acetylglucosamine-3-enolpyruvyltransferase, also known as MurA. This enzyme catalyzes the committed step in peptidoglycan biosynthesis, namely the ligation of phosphoenolpyruvate (PEP) to the 3'-hydroxyl group of UDP-N-acetylglucosamine. This pyruvate moiety provides the linker that bridges the glycan and peptide portion of peptidoglycan. Fosfomycin is a PEP analog that inhibits MurA by alkylating an active site cysteine residue (Cys 115 in the Escherichia coli enzyme).
Fosfomycin enters the bacterial cell through the glycerophosphate transporter. 
Antibacterial spectrum and susceptibility
Fosfomycin has broad antibacterial activity against both Gram-positive and Gram-negative pathogens, with useful activity against E. faecalis, E. coli, and various Gram-negatives like Citrobacter and Proteus. Given a greater activity in a low pH milieu, and predominant excretion in active form into the urine, fosfomycin has found use for the prophylaxis and treatment of urinary tract infections caused by these uropathogens. Of note, activity against S. saprophyticus, Klebsiella and Enterobacter is variable and should be confirmed by minimum inhibitory concentration (MIC) testing. Activity against extended-spectrum β-lactamase (ESBL)-producing pathogens, notably ESBL-producing E. coli is good to excellent, because the drug is not affected by cross-resistance issues. Existing clinical data support use in uncomplicated UTI, caused by susceptible organisms. However, susceptibility break-points of 64 mg/L should not be applied for systemic infections.
Biosynthetic gene cluster
The complete fosfomycin biosynthetic gene cluster from Streptomyces fradiae has been cloned and sequenced and the heterologous production of fosfomycin in Streptomyces lividans has been achieved by Ryan Woodyer of the Huimin Zhao and Wilfred van der Donk research groups.
Fosfomycin resistance enzymes
Three related fosfomycin resistance enzymes (named FosA, FosB, and FosX) are members of the glyoxalase superfamily. These enzymes function by nucleophilic attack on carbon 1 of fosfomycin, which opens the epoxide ring and renders the drug ineffective. The enzymes differ by the identity of the nucleophile utilized in the reaction: glutathione for FosA, bacillithiol for FosB, and water for FosX. In general, FosA and FosX enzymes are produced by Gram-negative bacteria, whereas FosB is produced by Gram-positive bacteria.
- Grif K, Dierich MP, Pfaller K, Miglioli PA, Allerberger F (Aug 2001). "In vitro activity of fosfomycin in combination with various antistaphylococcal substances". The Journal of Antimicrobial Chemotherapy 48 (2): 209–17. doi:10.1093/jac/48.2.209. PMID 11481290.
- Silver, L.L. Rational approaches to antibiotic discovery: pre-genomic directed and phenotypic screening, 2.4.2 Screens for spheroplast formation. In: Thomas Dougherty, Michael J. Pucci, Antibiotic Discovery and Development. Chap. 2, p. 46.
- Encros About us: Our history.
- Patel SS, Balfour JA, Bryson HM (Apr 1997). "Fosfomycin tromethamine. A review of its antibacterial activity, pharmacokinetic properties and therapeutic efficacy as a single-dose oral treatment for acute uncomplicated lower urinary tract infections". Drugs 53 (4): 637–656. doi:10.2165/00003495-199753040-00007. PMID 9098664.
- Trapnell BC, McColley SA, Kissner DG, Rolfe MW, Rosen JM, McKevitt M, Moorehead L, Montgomery AB, Geller DE (Jan 2012). "Fosfomycin/tobramycin for inhalation in patients with cystic fibrosis with pseudomonas airway infection". American Journal of Respiratory and Critical Care Medicine 185 (2): 171–8. doi:10.1164/rccm.201105-0924OC. PMID 22095545.
- Clinical trial number NCT00794586 for "Study Evaluating Fosfomycin/Tobramycin for Inhalation in Cystic Fibrosis Patients With Pseudomonas Aeruginosa Lung Infection" at ClinicalTrials.gov
- "MONURIL SACHETS 3G". Retrieved May 26, 2014.
- Falagas ME, Giannopoulou KP, Kokolakis GN, Rafailidis PI (Apr 2008). "Fosfomycin: use beyond urinary tract and gastrointestinal infections". Clinical Infectious Diseases 46 (7): 1069–77. doi:10.1086/527442. PMID 18444827.
- Falagas ME, Grammatikos AP, Michalopoulos A (Oct 2008). "Potential of old-generation antibiotics to address current need for new antibiotics". Expert Review of Anti-Infective Therapy 6 (5): 593–600. doi:10.1586/14787220.127.116.113. PMID 18847400.
- Brown ED, Vivas EI, Walsh CT, Kolter R (Jul 1995). "MurA (MurZ), the enzyme that catalyzes the first committed step in peptidoglycan biosynthesis, is essential in Escherichia coli". Journal of Bacteriology 177 (14): 4194–7. PMC 177162. PMID 7608103.
- "Cell Envelope.1995". Retrieved 2008-11-08.
- Santoro A, Cappello AR, Madeo M, Martello E, Iacopetta D, Dolce V (Jul 2011). "Interaction of fosfomycin with the glycerol 3-phosphate transporter of Escherichia coli.". Biochimica et Biophysica Acta 1810 (12): 1323–1329. doi:10.1016/j.bbagen.2011.07.006. PMID 21791237.
- Woodyer RD, Shao Z, Thomas PM, Kelleher NL, Blodgett JA, Metcalf WW, van der Donk WA, Zhao H (Nov 2006). "Heterologous production of fosfomycin and identification of the minimal biosynthetic gene cluster". Chemistry & Biology 13 (11): 1171–82. doi:10.1016/j.chembiol.2006.09.007. PMID 17113999.
- Kahan FM, Kahan JS, Cassidy PJ, Kropp H (May 1974). "The mechanism of action of fosfomycin (phosphonomycin)". Annals of the New York Academy of Sciences 235 (0): 364–386. Bibcode:1974NYASA.235..364K. doi:10.1111/j.1749-6632.1974.tb43277.x. PMID 4605290.
- Rigsby RE, Fillgrove KL, Beihoffer LA, Armstrong RN (2005). "Fosfomycin resistance proteins: a nexus of glutathione transferases and epoxide hydrolases in a metalloenzyme superfamily". Methods in Enzymology. Methods in Enzymology 401: 367–379. doi:10.1016/S0076-6879(05)01023-2. ISBN 9780121828066. PMID 16399398.
- Sharma SV, Jothivasan VK, Newton GL, Upton H, Wakabayashi JI, Kane MG, Roberts AA, Rawat M, La Clair JJ, Hamilton CJ (Jul 2011). "Chemical and Chemoenzymatic syntheses of bacillithiol: a unique low-molecular-weight thiol amongst low G + C Gram-positive bacteria". Angewandte Chemie 50 (31): 7101–7104. doi:10.1002/anie.201100196. PMID 21751306.
- Roberts AA, Sharma SV, Strankman AW, Duran SR, Rawat M, Hamilton CJ (Apr 2013). "Mechanistic studies of FosB: a divalent-metal-dependent bacillithiol-S-transferase that mediates fosfomycin resistance in Staphylococcus aureus". The Biochemical Journal 451 (1): 69–79. doi:10.1042/BJ20121541. PMID 23256780.
- García P, Arca P, Evaristo Suárez J (Jul 1995). "Product of fosC, a gene from Pseudomonas syringae, mediates fosfomycin resistance by using ATP as cosubstrate". Antimicrobial Agents and Chemotherapy 39 (7): 1569–73. doi:10.1128/aac.39.7.1569. PMC 162783. PMID 7492106.