2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 July 2017 - 15 August 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide

EC Number:

253-021-4

EC Name:

2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide

Cas Number:

36411-52-6

Molecular formula:

C9H8N4O2

IUPAC Name:

2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide

Test material form:

solid: particulate/powder

Details on test material:

Batch:102Z5
Purity: 99.9%
white powder

Method

Target gene:

Histidine or Tryptophan locus in the genome of five strains of bacteria.

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Details on mammalian cell type (if applicable):

CELLS USED
The bacteria used in the test were obtained from:
• University of California, Berkeley, on culture discs, on 04 August 1995
• British Industrial Biological Research Association, on a nutrient agar plate, on 17 August 1987
All of the strains were stored at approximately -196 °C in a Statebourne liquid nitrogen freezer, model SXR 34. In this assay, overnight sub-cultures of the appropriate coded stock cultures were prepared in nutrient broth (Oxoid Limited; lot number 1865318 05/21) and incubated at 37 °C for approximately 10 hours. Each culture was monitored spectrophotometrically for turbidity with titres determined by viable count analysis on nutrient agar plates.

MEDIA USED
Top agar was prepared using 0.6% Bacto agar (lot number 6221620 06/21) and 0.5% sodium chloride with 5 mL of 1.0 mM histidine and 1.0 mM biotin or 1.0 mM tryptophan solution added to each 100 mL of top agar. Vogel-Bonner Minimal agar plates were purchased from SGL Ltd (lot numbers 44951 08/17 and 45010 09/17).

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

S9

Test concentrations with justification for top dose:

Experiment 1: Eight concentrations of the test item (1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate) were assayed in triplicate against each tester strain, using the direct plate incorporation method.
Experiment 2: Pre-incubation method - The dose range used for Experiment 2 was determined by the results of Experiment 1 and was 15, 50, 150, 500, 1500, 5000 μg/plate.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: dimethyl formamide
- Justification for choice of solvent/vehicle: The test item formed the best doseable suspension in dimethyl formamide, therefore, this solvent was selected as the vehicle.

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

9-aminoacridine

N-ethyl-N-nitro-N-nitrosoguanidine

benzo(a)pyrene

other: 2-Aminoanthracene (2AA)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium; 2 mL of molten, trace amino-acid supplemented media. These were then mixed and overlayed onto a Vogel-Bonner agar plate. Negative (untreated) controls were also performed on the same day as the mutation test. Each concentration of the test item, appropriate positive, vehicle and negative controls, and each bacterial strain, was assayed using triplicate plates.

DURATION
All of the plates were incubated at 37 ± 3 °C for approximately 48 hours and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning (toxicity). Several manual counts were required due to revertant colonies spreading slightly, thus distorting the actual plate count.

Rationale for test conditions:

Guideline

Evaluation criteria:

Criteria for determining a positive result. Any, one, or all of the following can be used to determine the overall result of the study:
1. A dose-related increase in mutant frequency over the dose range tested (De Serres and Shelby, 1979).
2. A reproducible increase at one or more concentrations.
3. Biological relevance against in-house historical control ranges.
4. Statistical analysis of data as determined by UKEMS (Mahon et al., 1989).
5. Fold increase greater than two times the concurrent solvent control for any tester strain (especially if accompanied by an out-of-historical range response (Cariello and Piegorsch, 1996)).
A test item will be considered non-mutagenic (negative) in the test system if the above criteria are not met.

Statistics:

Dunnetts Regression Analysis (* = p < 0.05) for those values that indicate statistically significant increases in the frequency of revertant colonies compared to the concurrent solvent control.

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 5

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Prior to use, the master strains were checked for characteristics, viability and spontaneous reversion rate (all were found to be satisfactory). The amino acid supplemented top agar and the S9-mix used in both experiments was shown to be sterile. The test item formulation was also shown to be sterile.

The vehicle (dimethyl formamide) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

There was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the first mutation test (plate incorporation method) and consequently, the same maximum dose level was used in the second mutation test. Similarly, there was no visible reduction in the growth of the bacterial background lawn at any dose level, either in the presence or absence of metabolic activation (S9-mix), in the second mutation test (pre-incubation method).

A test item precipitate (white and powdery in appearance) was noted at and above 1500 μg/plate, this observation did not prevent the scoring of revertant colonies.
There were no increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 1 (plate incorporation method). Similarly, no increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 2 (pre-incubation method).

Applicant's summary and conclusion

Conclusions:

CDA-1 was considered to be non-mutagenic under the conditions of this test.