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Explore antimicrobial resistance genes from the literature

dfrA18

trimethoprim-resistant dihydrofolate reductase DfrA18

NCBI Pathogen Isolates

Bacterial genomes carrying this gene

NCBI Reference Gene Catalog

Known alleles and reference sequences

Protein entries specific to dfrA18

Browse AMR rules for dfrA18

Validation StatusConfirmed2+ DBs

Overview

Mechanism: Purine synthesis
Validation Method: whole-genome sequencing and plasmid analysis
Drug Classes: TRIMETHOPRIM, Trimethoprim
Organisms: Vibrio cholerae MO10, Enterobacter spp., Serratia marcescens, Citrobacter, Salmonella enterica, Citrobacter freundii, Citrobacter koseri, Citrobacter portucalensis, Escherichia coli, Vibrio cholerae
Geographic Location: Europe, Europe|Denmark|France|Germany|United Kingdom, Germany, Pakistan, United States|New York|Florida|Illinois|Gaza|Colombia|South America|Mediterranean region
Alleles: 3
Papers: 8
Databases: Card DatabaseReference Gene CatalogResFinder DatabaseReslit

Allele Variants3

Allele	Database	Papers	Drug Classes	Organisms	Countries	Years	Sequence Accession	Protein Accession
dfrA18	Card DatabaseResFinder Database	2	TRIMETHOPRIM	Vibrio cholerae MO10	-	2001	AY034138	AAK64581.1
DfrA18

Papers8

1

Molecular analysis of antibiotic resistance gene clusters in vibrio cholerae O139 and O1 SXT constins.

PMID 11600347 · 2001

Gene Information

Gene Name: dfrA18
Allele: dfrA18
Source Database: ResFinder Database
Mechanism: Purine synthesis
Confers Resistance To: TRIMETHOPRIM
Organisms Tested In: • Vibrio cholerae MO10
Sequence Accession: AY034138

2

Molecular analysis of antibiotic resistance gene clusters in vibrio cholerae O139 and O1 SXT constins.

PMID 11600347 · 2001

Gene Information

Gene Name: dfrA18
Allele: DfrA18
Encodes: trimethoprim-resistant dihydrofolate reductase DfrA18
Source Database: Card Database
Mechanism: Purine synthesis
Confers Resistance To: TRIMETHOPRIM
Organisms Tested In: • Vibrio cholerae MO10
Sequence Accession: AY034138.1
Protein Accession: AAK64581.1
Notes: ARO:3004568

3

Molecular analysis of antibiotic resistance gene clusters in vibrio cholerae O139 and O1 SXT constins.

PMID 11600347 · 2001

Gene Information

Gene Name: dfrA18
Allele: DfrA18
Encodes: trimethoprim-resistant dihydrofolate reductase DfrA18
Source Database: ResFinder Database
Mechanism: Purine synthesis
Confers Resistance To: TRIMETHOPRIM
Organisms Tested In: • Vibrio cholerae MO10
Sequence Accession: AY034138.1
Protein Accession: AAK64581.1
Notes: ARO:3004568

4

Molecular analysis of antibiotic resistance gene clusters in vibrio cholerae O139 and O1 SXT constins.

PMID 11600347 · 2001

Gene Information

Gene Name: dfrA18
Allele: DfrA18
Encodes: trimethoprim-resistant dihydrofolate reductase DfrA18
Source Database: Reference Gene Catalog
Mechanism: Purine synthesis
Confers Resistance To: TRIMETHOPRIM
Organisms Tested In: • Vibrio cholerae MO10
Sequence Accession: AY034138.1
Protein Accession: AAK64581.1
Notes: ARO:3004568

5

Comprehensive Genome Analysis of Carbapenemase-Producing Enterobacter spp.: New Insights into Phylogeny, Population Structure, and Resistance Mechanisms.

PMID 27965456 · 2016

The study identifies multiple carbapenemase genes (bla KPC-2, bla KPC-3, bla KPC-4, and bla NDM-1) and other resistance genes (such as qnrB19, qnrB2, qnrS1, bla TEM-1A, bla TEM-1B, bla OXA-9, bla SHV-12, aadA2, aac(6')-Ib, aac(6')-Ib-cr, aph(3')-Ia, aph(3')-Ic, strA, strB, sul1, sul2, dfrA14, dfrA18, mph(A), catB3, arr-3, and tet(D)) in carbapenem-resistant Enterobacter spp. These genes are primarily located on plasmids and contribute to multidrug resistance.

Gene Information

Gene Name: dfrA18
Allele: DfrA18
Encodes: dihydrofolate reductase
Source Database: Reslit
Confers Resistance To: Trimethoprim
Organisms Tested In: • Enterobacter spp.
Geographic Location: United States|New York|Florida|Illinois|Gaza|Colombia|South America|Mediterranean region
Validation Method: whole-genome sequencing and plasmid analysis
Sequence Accession: NZ_CP017183.1|NZ_CP017179.1|NZ_CP017180.1|NZ_CP017186.1|GCA_000213995.1|NC_014121.1|NZ_CP011863.1|NZ_CP017181.1|NZ_CP017184.1|PRJNA259658

6

Draft Genome Sequences of Pandrug-Resistant Serratia marcescens Clinical Isolates Harboring blaNDM-1.

PMID 28104656 · 2017

The study reports the draft genome sequences of two pandrug-resistant Serratia marcescens clinical isolates carrying multiple antibiotic resistance genes, including blaNDM-1, blaSHV-12, blaTEM-1B, blaCMY-6, sul1, sul2, rmtC, aacA4, aac(6')Ib-c, strA, strB, dfrA18, qnrA1, catA2, aac(6')-Ic, tet(41), and ampC.

Gene Information

Gene Name: dfrA18
Allele: DfrA18
Encodes: dihydrofolate reductase
Source Database: Reslit
Confers Resistance To: Trimethoprim
Organisms Tested In: • Serratia marcescens
Geographic Location: Europe
Validation Method: whole-genome sequencing
Sequence Accession: FNXV00000000|FNXW00000000|FNXV01000000|FNXW01000000

7

Superficieibacter electus gen. nov., sp. nov., an Extended-Spectrum β-Lactamase Possessing Member of the Enterobacteriaceae Family, Isolated From Intensive Care Unit Surfaces.

PMID 30079059 · 2018

The study identifies multiple antibiotic resistance genes in the newly described species Superficieibacter electus, including beta-lactamases, aminoglycoside modifying enzymes, and others, indicating its ability to resist various antibiotics.

Gene Information

Gene Name: dfrA18
Allele: DfrA18
Encodes: dihydrofolate reductase
Source Database: Reslit
Confers Resistance To: Trimethoprim
Organisms Tested In: • Citrobacter
Geographic Location: Pakistan
Validation Method: ResFinder annotation
Sequence Accession: MG866003|PRJNA395420|ATCC BAA-2937|NBRC 113412

8

The Spatiotemporal Dynamics and Microevolution Events That Favored the Success of the Highly Clonal Multidrug-Resistant Monophasic Salmonella Typhimurium Circulating in Europe.

PMID 34093465 · 2021

The study identifies various AMR genes in the highly clonal multidrug-resistant monophasic Salmonella Typhimurium ST34, including beta-lactamases, sulfonamide resistance genes, tetracycline resistance genes, phenicol resistance genes, and polymyxin resistance genes.

Gene Information

Gene Name: dfrA18
Allele: dfrA1_8
Encodes: trimethoprim resistance
Source Database: Reslit
Confers Resistance To: Trimethoprim
Organisms Tested In: • Salmonella enterica
Geographic Location: Europe|Denmark|France|Germany|United Kingdom
Validation Method: plasmid analysis and sequencing
Sequence Accession: MF684783.1|CP055956.1|CP057682.1|CP055697.1|KF152885|HQ023861|KC853435.1|CP039562.1|MF543359.1

9

Carbapenem-Resistant Citrobacter spp. as an Emerging Concern in the Hospital-Setting: Results From a Genome-Based Regional Surveillance Study.

PMID 34858870 · 2021

The study identifies various carbapenemase genes, including bla KPC-2, bla OXA-48, bla VIM-1, bla NDM-5, bla OXA-162, and bla KPC-3, in Citrobacter spp. isolates, highlighting their role in carbapenem resistance.

Gene Information

Gene Name: dfrA18
Allele: DfrA18
Encodes: Dihydrofolate reductase
Source Database: Reslit
Confers Resistance To: Trimethoprim
Organisms Tested In: • Citrobacter freundii
• Citrobacter koseri
• Citrobacter portucalensis
Geographic Location: Germany
Validation Method: plasmid sequencing and cloning
Sequence Accession: CP049015|BBMV01000001|pCF13066-KPC2|pCF37969-KPC2|PRJNA692829

10

Zoonotic potential of uropathogenic Escherichia coli lineages from companion animals.

PMID 40140916 · 2025

The study identified several antimicrobial resistance genes in uropathogenic E. coli strains from companion animals, including blaTEM-1b, sul1, sul2, dfrA1_10, dfrA17_1, dfrA1_8, dfrA7_5, gyrA_S83L, tetA, tetB, aph(6)-Id, aph(3'')-Ib, ant(3'')-Ia, blaCTX-M-15, blaTEM-106, blaSHV-102, and blaCMY-2. These genes confer resistance to various antibiotics such as penicillins, sulfonamides, trimethoprim, quinolones, tetracyclines, streptomycin, and cephalosporins.

Gene Information

Gene Name: dfrA18
Allele: dfrA1_8
Encodes: dihydrofolate reductase
Source Database: Reslit
Mechanism: resistance to trimethoprim
Confers Resistance To: Trimethoprim
Organisms Tested In: • Escherichia coli
Geographic Location: Europe
Validation Method: whole genome analysis

11

Unraveling the role of mobile genetic elements in antibiotic resistance transmission and defense strategies in bacteria.

PMID 40810119 · 2025

The study characterizes several AMR genes, including blaIPM-4, blaOXA-1, blaOXA-10, aacA4, blaOXA-101, aadA11, aadA9, qacEΔ1, sat2-aadA1, and others, highlighting their role in conferring resistance to various antibiotics in different bacterial species.

Gene Information

Gene Name: dfrA18
Allele: DfrA18
Encodes: Dihydrofolate reductase
Source Database: Reslit
Confers Resistance To: Trimethoprim
Organisms Tested In: • Vibrio cholerae
Validation Method: gene characterization

12

Gene Information

Gene Name: dfrA18
Allele: dfrA18
Encodes: trimethoprim resistant dihydrofolate reductase dfr
Source Database: Card Database
Mechanism: antibiotic target replacement
Organisms Tested In: • Vibrio cholerae MO10
Sequence Accession: AY034138.1
Protein Accession: AAK64581.1
Notes: ARO:3004568