Accession ARO:3000172
CARD Short NameFosB
DefinitionA thiol transferase that leads to the resistance of fosfomycin. Contrasting FosA, FosB is dependent on the cofactor Magnesium (II) and uses either bacillithiol or L-cysteine to open up the epoxide ring of fosfomycin.
AMR Gene Familyfosfomycin thiol transferase
Drug Classphosphonic acid antibiotic
Resistance Mechanismantibiotic inactivation
Resistomes with Perfect MatchesBacillus cereusg+wgs
Resistomes with Sequence VariantsBacillus anthracisg+wgs, Bacillus cereusg+wgs, Bacillus thuringiensisg+wgs
Classification10 ontology terms | Show
Parent Term(s)2 ontology terms | Show
+ fosfomycin thiol transferase [AMR Gene Family]
+ confers_resistance_to_antibiotic fosfomycin [Antibiotic]

Thompson MK, et al. 2014. Biochemistry 53(4): 755-765. Structure and Function of the Genomically Encoded Fosfomycin Resistance Enzyme, FosB, from Staphylococcus aureus. (PMID 24447055)

Thompson MK, et al. 2013. Biochemistry 52(41): 7350-7362. Structural and chemical aspects of resistance to the antibiotic fosfomycin conferred by FosB from Bacillus cereus. (PMID 24004181)


Prevalence of FosB among the sequenced genomes, plasmids, and whole-genome shotgun assemblies available at NCBI or IslandViewer for 413 important pathogens (see methodological details and complete list of analyzed pathogens). Values reflect percentage of genomes, plasmids, genome islands, or whole-genome shotgun assemblies that have at least one hit to the AMR detection model. Default view includes percentages calculated based on Perfect plus Strict RGI hits. Select the checkbox to view percentages based on only Perfect matches to AMR reference sequences curated in CARD (note: this excludes resistance via mutation as references in protein variant models are often wild-type, sensitive sequences).

Prevalence: protein homolog model (view sequences)

SpeciesNCBI ChromosomeNCBI PlasmidNCBI WGSNCBI GI
Bacillus anthracis97.54%0%76.75%0%
Bacillus cereus93.55%0%82.25%0%
Bacillus thuringiensis96.25%0%63.53%0%
Show Perfect Only

Detection Models

Model Type: protein homolog model

Model Definition: Protein Homolog Models (PHM) detect protein sequences based on their similarity to a curated reference sequence, using curated BLASTP bitscore cut-offs. Protein Homolog Models apply to all genes that confer resistance through their presence in an organism, such as the presence of a beta-lactamase gene on a plasmid. PHMs include a reference sequence and a bitscore cut-off for detection using BLASTP. A Perfect RGI match is 100% identical to the reference protein sequence along its entire length, a Strict RGI match is not identical but the bit-score of the matched sequence is greater than the curated BLASTP bit-score cutoff, Loose RGI matches have a bit-score less than the curated BLASTP bit-score cut-off.

Bit-score Cut-off (blastP): 225

>gb|AAP08996.1|+|FosB [Bacillus cereus ATCC 14579]

>gb|AE016877.1|+|1972252-1972668|FosB [Bacillus cereus ATCC 14579]