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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
From June 08, 2017 to June 22, 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
no analytical veryfication
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder

Method

Species / strain
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Metabolic activation:
with and without
Metabolic activation system:
S9 fraction (10% liver in standard co-factors)
Test concentrations with justification for top dose:
Experiment 1: All strains (with and without S9-mix): 1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate.
Experiment 2: The dose range used was determined by the results of Experiment 1. All strains (with and without S9-mix): 15, 50, 150, 500, 1500, 5000 μg/plate.
Vehicle / solvent:
Identity: Sterile distilled water
Supplier: Aguettant
Batch number (purity): 3012436 (N/A)
Exp: 10/2018
Controls
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
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:
Preparation of the test substance formulations:
The test substance was accurately weighed and approximate half-log dilutions prepared in sterile distilled water by mixing on a vortex mixer and sonication for 20 minutes at 40 °C on the day of each experiment. No correction for purity was required.

EXPERIMENT 1: direct plate incorporation method,
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.

Without Metabolic Activation:
0.1 mL of the appropriate concentration of test substance, solvent vehicle or appropriate positive control was added together with 0.1 mL of one of the bacterial strain cultures and 0.5 mL of phosphate buffer to 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 substance, appropriate positive, vehicle and negative controls, and each bacterial strain, was assayed using triplicate plates.

With Metabolic Activation:
The procedure was the same as for without of metabolic activation except that following the addition of the test substance formulation and bacterial culture, 0.5 mL of S9-mix was added to the molten, trace amino-acid supplemented media instead of phosphate buffer.

Incubation and Scoring:
All of the plates were incubated at 37 ± 3 °C for approximately 48 h and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning (toxicity). Manual counts were performed at 5000 μg/plate (presence of S9-mix only) because of a patchy test substance precipitation.

EXPERIMENT 2:

Without Metabolic Activation:
0.1 mL of the appropriate bacterial strain culture, 0.5 mL of phosphate buffer and 0.1 mL of the test subsatnce formulation, solvent vehicle or 0.1 mL of appropriate positive control were incubated at 37 ± 3 °C for 20 minutes (with shaking) prior to addition of 2 mL of molten, trace amino-acid supplemented media and subsequent plating onto Vogel-Bonner plates. Negative (untreated) controls were also performed on the same day as the mutation test employing the plate incorporation method. All testing for this experiment was performed in triplicate.

With Metabolic Activation:
The procedure was the same as described above except that following the addition of the test substance formulation and bacterial strain culture, 0.5 mL of S9-mix was added to the tube instead of phosphate buffer, prior to incubation at 37 ± 3 °C for 20 minutes (with shaking) and addition of molten, trace amino-acid supplemented media. All testing for this experiment was performed in triplicate.

Incubation and Scoring:
All of the plates were incubated at 37 ± 3 °C for approximately 48 h and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning (toxicity). Manual counts were performed at and above 1500 μg/plate (presence and absence of S9-mix only) because of test substance precipitation. Several further manual counts were also required due to revertant colonies spreading slightly, thus distorting the actual plate count.
Rationale for test conditions:
The test substance was insoluble in sterile distilled water, dimethyl sulphoxide, dimethyl formamide and acetonitrile at 50 mg/mL, acetone at 100 mg/mL and tetrahydrofuran at 200 mg/mL in solubility checks performed in–house. The test substance formed the best doseable suspension in sterile distilled water, therefore, this solvent was selected as the vehicle.
Evaluation criteria:
There are several criteria for determining positive result. Any one or all of the following can be used to determine overall result of the study:
1. 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. Statystical analysis of data as determined by UKEMS (Mahon et al. 1989).
5. Fold increase greater than two times the concurent solvent control for any tester strain (especially if acompanied by out-of-historical range response (Cariello and Piegorsch, 1996)).
A test substance will be considered non-mutagenic (negative) in the test system if the above criteria are not met.Although most experiments will give clear positive or negative results, is some instances the data generated will prohibit making a definite judgment about test substance activity. Results of this type will be reported as equivocal.
Statistics:
Statistical significance was confirmed by using 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
Key result
Species / strain:
other: S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Positive controls validity:
valid
Additional information on results:
- 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 substance precipitate (particulate 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 substance, 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 substance, either with or without metabolic activation (S9-mix), in Experiment 2 (pre-incubation method).
- The vehicle (sterile distilled water) control plates gave counts of revertant colonies generally 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.

Applicant's summary and conclusion

Conclusions:
Under the study conditions, the test substance was determined to be non-genotoxic with and without metabolic activation.


Executive summary:

A study was conducted to determine the genotoxic potential of test substance, 'mono- and di- C16 PSE, K+ and H3PO4' (purity: 100%), using Ames test, according to OECD Guideline 471 and EU Method B13/14, in compliance with GLP. Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 and Escherichia coli strain WP2uvrA were treated with suspensions of the test substance using both the Ames plate incorporation and pre-incubation methods at up to eight dose levels (i.e., 1.5, 5, 15, 50, 150, 500, 1500 and 5000 µg/plate), in triplicate, both with and without metabolic activation (10% liver S9 in standard co-factors). The dose range for Experiment 1 was predetermined and ranged from 1.5 to 5000 μg/plate. The experiment was repeated on a separate day (pre-incubation method) using fresh cultures of the bacterial strains and fresh test substance formulations. The dose range was amended following the results of Experiment 1 and was 15 to 5000 μg/plate. Six test substance concentrations per bacterial strain were selected in Experiment 2 in order to achieve both four non-toxic dose levels and the potential toxic limit of the test substance following the change in test methodology. The vehicle (sterile distilled water) control plates gave counts of revertant colonies generally 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 second mutation test (pre-incubation method). A test substance precipitate (particulate 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 substance, either with or without metabolic activation (S9-mix), in Experiment 1 (plate incorporation method) and 2 (pre-incubation method). Under the study conditions, the test substance was determined to be non-genotoxic in the Ames test, with and without metabolic activation (Envigo, 2017).