metronidazole

CHEBI:6909 ·resolve ·ANTIBACTERIAL ·EXACT SEEDED

A member of the class of imidazoles substituted at C-1, -2 and -5 with 2-hydroxyethyl, nitro and methyl groups respectively. It has activity against anaerobic bacteria and protozoa, and has a radiosensitising effect on hypoxic tumour cells. It may be given by mouth in tablets, or as the benzoate in an oral suspension. The hydrochloride salt can be used in intravenous infusions. Metronidazole is a prodrug and is selective for anaerobic bacteria due to their ability to intracellularly reduce the nitro group of metronidazole to give nitroso-containing intermediates. These can covalently bind to DNA, disrupting its helical structure, inducing DNA strand breaks and inhibiting bacterial nucleic acid synthesis, ultimately resulting in bacterial cell death. — ChEBI

Machine-generated and unreviewed. Identity, structure and cross-references come straight from ChEBI's and CARD's own data; no curator has signed off on this record yet.

Classification

nitroimidazole antibioticARO:3004115

Strictly broader compounds or drug classes this molecule belongs to.

Label unavailable CHEBI:15734
Label unavailable CHEBI:24780
Label unavailable CHEBI:35716
nitroimidazole antibiotic ARO:3004115

Chemical structure

Computed structure properties
Molecular formula	C6H9N3O3
Charge	0
Average mass	171.156 Da
Monoisotopic mass	171.06439 Da
Source	ChEBI
InChIKey	VAOCPAMSLUNLGC-UHFFFAOYSA-N

SMILES

Cc1ncc([N+](=O)[O-])n1CCO

InChI

InChI=1S/C6H9N3O3/c1-5-7-4-6(9(11)12)8(5)2-3-10/h4,10H,2-3H2,1H3

Also called

metronidazol (INN)— chebi
metronidazolum (INN)— chebi
métronidazole (INN)— chebi
2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethanol (EXACT_SYNONYM)— chebi
1-(2-hydroxy-1-ethyl)-2-methyl-5-nitroimidazole (EXACT_SYNONYM)— chebi
1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole (EXACT_SYNONYM)— chebi
1-(β-ethylol)-2-methyl-5-nitro-3-azapyrrole (EXACT_SYNONYM)— chebi
1-(β-hydroxyethyl)-2-methyl-5-nitroimidazole (EXACT_SYNONYM)— chebi
1-(β-oxyethyl)-2-methyl-5-nitroimidazole (EXACT_SYNONYM)— chebi
2-methyl-1-(2-hydroxyethyl)-5-nitroimidazole (EXACT_SYNONYM)— chebi
2-methyl-3-(2-hydroxyethyl)-4-nitroimidazole (EXACT_SYNONYM)— chebi
2-methyl-5-nitroimidazole-1-ethanol (EXACT_SYNONYM)— chebi
Flagyl (EXACT_SYNONYM)— aro

Cross-references

Identifiers for this same structure in other resources. An accession that lands on two different structures in this corpus is withheld from both rather than shown here, since it names at most one of them.

Drug registries

Identifiers that name a drug rather than a structure. One of these can cover a parent compound, its salts and its stereoisomers, which this corpus keeps as separate records, so it is not an equivalence of structure.

Patents and articles

Documents about this compound. A patent covers a class and an article covers a topic; neither identifies a structure.

Activity roles

Every antimicrobial role a source asserts for this compound — the unreduced evidence behind its antimicrobial_class.

antimicrobial agent CHEBI:33281
antibacterial drug CHEBI:36047
antitrichomonal drug CHEBI:50685

Source concepts

Every upstream concept that resolved to this record. The merge is the product: this is what shows ChEBI and CARD are describing the same structure.

Upstream concepts merged into this record
Source	Native ID	Label	Minted CURIE	Version
ARO	`ARO:3000689`	metronidazole	`antibioticmech:aro-a369adefb4`	2026-08-30
CHEBI	`CHEBI:6909`	metronidazole	`antibioticmech:chebi-daf94f3c73`	2026-08-30

Molecular targets

The molecular entity or process this compound acts on. Each target carries evidence — this is a mechanistic claim, not a classification.

anaerobe DNA NUCLEIC_ACID ATTACKED_COMPONENT

ARO:3000742

CARD/ARO database assertion; target organism, strain, and assay are not specified. Activated nitroimidazole intermediates attack DNA in anaerobic context. Evidence status: DATABASE_ASSERTION_ONLY. Source: CARD_ARO 2026-08-30 (retrieved 2026-08-30).

ARO:3000742 (CARD/ARO asserts targeted_by_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)

Mechanism summary

Clinical status: APPROVED

Resistance mechanisms

23 source-backed resistance determinants or associations, with ARO grounding where reported. Grouped by reported mechanism type.

ANTIBIOTIC_INACTIVATION 12

ANTIBIOTIC_INACTIVATION
Determinant	ARO ID	Organism	Gene families	Evidence
Clostridioides difficile nimB	ARO:3007671	not organism-specific	—	ARO:3007671 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimA	ARO:3007104	not organism-specific	—	ARO:3007104 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimB	ARO:3004655	not organism-specific	—	ARO:3004655 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimC	ARO:3007105	not organism-specific	—	ARO:3007105 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimD	ARO:3007106	not organism-specific	—	ARO:3007106 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimE	ARO:3007107	not organism-specific	—	ARO:3007107 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimF	ARO:3007108	not organism-specific	—	ARO:3007108 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimG	ARO:3007109	not organism-specific	—	ARO:3007109 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimH	ARO:3007110	not organism-specific	—	ARO:3007110 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimI	ARO:3007111	not organism-specific	—	ARO:3007111 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimJ	ARO:3007112	not organism-specific	—	ARO:3007112 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
nimK	ARO:3007113	not organism-specific	—	ARO:3007113 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)

UNKNOWN 5

UNKNOWN
Determinant	ARO ID	Organism	Gene families	Evidence
nimB-associated reduced metronidazole susceptibility in clinical isolate ARU 11562 Same-isolate gene-type/phenotype co-occurrence, not allele-specific causation. Gene type was assigned by PCR-RFLP, not exact allele sequencing. No protein accession, strain TaxID, genome or numerical AST is assigned. Compound scope follows named metronidazole; the tested preparation was not independently re-identified.	—	Bacteroides fragilis `NCBITaxon:817` strain ARU 11562	nimB	PMID:10970359 (Primary Table 2 clinical isolate, distinct from controls and nimE rows; Methods and Results inspected as publisher text.) Source-reported gradient diffusion (Etest) phenotype
nimB-associated reduced metronidazole susceptibility in clinical isolate ARU 12371 Same-isolate gene-type/phenotype co-occurrence, not allele-specific causation. Gene type was assigned by PCR-RFLP, not exact allele sequencing. No protein accession, strain TaxID, genome or numerical AST is assigned. Compound scope follows named metronidazole; the tested preparation was not independently re-identified.	—	Bacteroides thetaiotaomicron `NCBITaxon:818` strain ARU 12371	nimB	PMID:10970359 (Primary Table 2 clinical isolate, distinct from controls and nimE rows; Methods and Results inspected as publisher text.) Source-reported gradient diffusion (Etest) phenotype
nimB-associated reduced metronidazole susceptibility in clinical isolate ARU 12963 Same-isolate gene-type/phenotype co-occurrence, not allele-specific causation. Gene type was assigned by PCR-RFLP, not exact allele sequencing. No protein accession, strain TaxID, genome or numerical AST is assigned. Compound scope follows named metronidazole; the tested preparation was not independently re-identified.	—	Bacteroides fragilis `NCBITaxon:817` strain ARU 12963	nimB	PMID:10970359 (Primary Table 2 clinical isolate, distinct from controls and nimE rows; Methods and Results inspected as publisher text.) Source-reported gradient diffusion (Etest) phenotype
nimB-associated reduced metronidazole susceptibility in clinical isolate ARU 7420 Same-isolate gene-type/phenotype co-occurrence, not allele-specific causation. Gene type was assigned by PCR-RFLP, not exact allele sequencing. No protein accession, strain TaxID, genome or numerical AST is assigned. Compound scope follows named metronidazole; the tested preparation was not independently re-identified.	—	Bacteroides fragilis `NCBITaxon:817` strain ARU 7420	nimB	PMID:10970359 (Primary Table 2 clinical isolate, distinct from controls and nimE rows; Methods and Results inspected as publisher text.) Source-reported gradient diffusion (Etest) phenotype
nimB-associated reduced metronidazole susceptibility in clinical isolate ARU 9750 Same-isolate gene-type/phenotype co-occurrence, not allele-specific causation. Gene type was assigned by PCR-RFLP, not exact allele sequencing. No protein accession, strain TaxID, genome or numerical AST is assigned. Compound scope follows named metronidazole; the tested preparation was not independently re-identified.	—	Bacteroides fragilis `NCBITaxon:817` strain ARU 9750	nimB	PMID:10970359 (Primary Table 2 clinical isolate, distinct from controls and nimE rows; Methods and Results inspected as publisher text.) Source-reported gradient diffusion (Etest) phenotype

ANTIBIOTIC_EFFLUX 3

ANTIBIOTIC_EFFLUX
Determinant	ARO ID	Organism	Gene families	Evidence
hp1181	ARO:3003964	not organism-specific	—	ARO:3003964 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
hp1184	ARO:3003965	not organism-specific	—	ARO:3003965 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
msbA	ARO:3003950	not organism-specific	—	ARO:3003950 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)

ANTIBIOTIC_TARGET_ALTERATION 3

ANTIBIOTIC_TARGET_ALTERATION
Determinant	ARO ID	Organism	Gene families	Evidence
Antibiotic resistant Helicobacter pylori nitroreductase	ARO:3007056	not organism-specific	—	ARO:3007056 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
Helicobacter pylori frxA mutation conferring resistance to metronidazole	ARO:3007059	not organism-specific	—	ARO:3007059 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)
Helicobacter pylori rdxA mutation conferring resistance to metronidazole	ARO:3007055	not organism-specific	—	ARO:3007055 (CARD/ARO asserts confers_resistance_to_antibiotic ARO:3000689 (metronidazole); database assertion, not a primary citation.)

Curation history

SEEDED_FROM_SOURCES 2026-08-30 · seed_from_sources
Seeded from data/raw/ inventories (ARO, CHEBI)
RESEEDED_FROM_SOURCES 2026-08-30 · seed_from_sources
Re-seeded from updated data/raw/ inventories
RESEEDED_FROM_SOURCES 2026-08-30 · seed_from_sources
Re-seeded from updated data/raw/ inventories
RESEEDED_FROM_SOURCES 2026-08-31 · seed_from_sources
Re-seeded from updated data/raw/ inventories
RESEEDED_FROM_SOURCES 2026-08-31 · seed_from_sources
Re-seeded from updated data/raw/ inventories
RESEEDED_FROM_SOURCES 2026-08-31 · seed_from_sources
Re-seeded from updated data/raw/ inventories
RESEEDED_FROM_SOURCES 2026-09-10 · seed_from_sources
Re-seeded from updated data/raw/ inventories
CURATED_RESISTANCE_EVIDENCE 2026-10-10 · codex · LLM-assisted
Added five clinical-isolate nimB/metronidazole gene-type co-occurrence claims from primary Table 2, with species taxonomy and no exact allele/protein assignment. Preserved source-owned claims, separate controls and nimE distinctions. Whole-record review remains open.

Provenance

Seeded by scripts/seed_from_sources.py from the committed inventories in data/raw/. View the record (YAML).

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