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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2nd April 2007 to 12th June 2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of relevant results.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2007
Report date:
2007

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
Date of inspection: 30th August 2005 Date of signature: 21st November 2005
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Sponsor's identification :C-C1
Description : Dark blue powder
Batch number : MB-1
Date received : 05 March 2007
Storage conditions :Room temperature in the dark over silica gel

Method

Target gene:
Histidine operon for Salmonella
Tryptophan operon for Escherichia
Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Details on mammalian cell type (if applicable):
Not applicable
Additional strain / cell type characteristics:
not applicable
Species / strain / cell type:
E. coli WP2 uvr A
Details on mammalian cell type (if applicable):
Not applicable
Additional strain / cell type characteristics:
not applicable
Metabolic activation:
with and without
Metabolic activation system:
Phenobarbitone / beta-naphthoflavone induced rat liver S9
Test concentrations with justification for top dose:
Preliminary toxicity test
0, 0.15, 0.5, 1.5, 5, 15, 50, 150, 500, 1500 and 5000 µg/plate

Mutation test - Experiment 1 (Range-finding test) and Experiment 2 (Main test)
0, 50, 150, 500, 1500 and 5000 µg/plate
Vehicle / solvent:
The test material was fully soluble in sterile distilled water at 50 mg/ml in solubility checks performed in-house. Sterile distilled water was therefore selected as the vehicle.
Controlsopen allclose all
Untreated negative controls:
yes
Remarks:
Spontaneous mutation rates
Negative solvent / vehicle controls:
yes
Remarks:
Sterile distilled water
True negative controls:
no
Positive controls:
yes
Positive control substance:
N-ethyl-N-nitro-N-nitrosoguanidine
Remarks:
2 µg/plate for WP2uvrA, 3 µg/plate for TA100 and 5 µg/plate for TA1535 without S9 mix
Untreated negative controls:
yes
Remarks:
Spontaneous mutation rates
Negative solvent / vehicle controls:
yes
Remarks:
Sterile distilled water
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
Remarks:
80 µg/plate for TA1537 without S9 mix
Untreated negative controls:
yes
Remarks:
Spontaneous mutation rates
Negative solvent / vehicle controls:
yes
Remarks:
Sterile distilled water
True negative controls:
no
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
Remarks:
0.2 µg/plate for TA98 without S9 mix
Untreated negative controls:
yes
Remarks:
Spontaneous mutation rates
Negative solvent / vehicle controls:
yes
Remarks:
Sterile distilled water
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-Aminoanthracene (2AA)
Remarks:
1 µg/plate for TA100, 2 µg/plate for TA1535 and TA1537 and 10 µg/plate for WP2uvrA with S9 mix
Untreated negative controls:
yes
Remarks:
Spontaneous mutation rates
Negative solvent / vehicle controls:
yes
Remarks:
Sterile distilled water
True negative controls:
no
Positive controls:
yes
Positive control substance:
benzo(a)pyrene
Remarks:
5 µg/plate for TA98 with S9 mix
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium; in agar (plate incorporation)

DURATION
- Exposure duration: 48 hours

NUMBER OF REPLICATIONS: triplicate plating

VOLUMES OF COLONIES EVALUATED: frequency of revertant colonies assessed using a Domino colony counter. Manual counts were performed at and above 1500 µg/plate because of an intense test material colouration.

DETERMINATION OF CYTOTOXICITY
- Method: lawn deficiency and colony reduction

OTHER EXAMINATIONS:
- Sterility (in preliminary toxicity test): The aliquot of 0.1 ml of maximum concentration of the test material (5000 µg/plate) and 2 ml of molten, trace histidine or tryptophan supplemented, top agar were overlaid onto a sterile Nutrient agar plate in order to assess the sterility of the test material.
Evaluation criteria:
Acceptance Criteria
The reverse mutation assay may be considered valid if the following criteria are met:
All tester strain cultures exhibit a characteristic number of spontaneous revertants per plate in the vehicle and untreated controls.
The appropriate characteristics for each tester strain have been confirmed, eg rfa cell-wall mutation and pKM101 plasmid R-factor etc.
All tester strain cultures should be in the approximate range of 1 to 9.9 x 109 bacteria per ml.
Each mean positive control value should be at least twice the respective vehicle control value for each strain, thus demonstrating both the intrinsic sensitivity of the tester strains to mutagenic exposure and the integrity of the S9-mix.
There should be a minimum of four non-toxic test material dose levels.
There should not be an excessive loss of plates due to contamination.

Evaluation Criteria
There are several criteria for determining a positive result, such as a dose-related increase in revertant frequency over the dose range tested and/or a reproducible increase at one or more concentrations in at least one bacterial strain with or without metabolic activation. Biological relevance of the results will be considered first, statistical methods, as recommended by the UKEMS can also be used as an aid to evaluation, however, statistical significance will not be the only determining factor for a positive response.
A test material 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, in some instances the data generated will prohibit a definitive judgement about the test material activity. Results of this type will be reported as equivocal.
Statistics:
UKEMS
Kirkland D J (Ed) (1989) Statistical Evaluation of Mutagenicity Test Data. UKEMS Subcommittee on Guidelines for Mutagenicity Testing, Report - Part III, Cambridge University Press.

Results and discussion

Test resultsopen allclose all
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Remarks:
but up to 5000 µg/plate
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Remarks:
but up to 5000 µg/plate
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation.

TEST-SPECIFIC CONFOUNDING FACTORS
- Water solubility: fullt soluble in sterile distilled water at 50 mg/ml
- Precipitation: No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix.
- Other confounding effects: A blue colour was noted from 50 µg/plate, this did not prevent the scoring of revertant colonies.

RANGE-FINDING/SCREENING STUDIES:
Preliminary Toxicity Test
The test material was non-toxic to the strains of bacteria used (TA100 and WP2uvrA-). The test material formulation and S9-mix used in this experiment were both shown to be sterile.

COMPARISON WITH HISTORICAL CONTROL DATA:
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.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative With and without metabolic activation

The test material was considered to be non-mutagenic under the conditions of this test.
Executive summary:

Introduction. The method was designed to conform to the guidelines for bacterial mutagenicity testing published by the major Japanese Regulatory Authorities including METI, MHLW and MAFF. It also meets the requirements of the OECD Guidelines for Testing of Chemicals No. 471 "Bacterial Reverse Mutation Test", Method B13/14 of Commission Directive 2000/32/EC and the, EPA (TSCA) OPPTS harmonised guidelines.

Methods. Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 and Escherichia coli strain WP2uvrA-were treated with the test material using the Ames plate incorporation method at five dose levels, in triplicate, both with and without the addition of a rat liver homogenate metabolising system (10% liver S9 in standard co-factors). The dose range for the range-finding test was determined in a preliminary toxicity assay and was 50 to 5000 µg/plate. The experiment was repeated on a separate day using the same dose range as the range-finding test, fresh cultures of the bacterial strains and fresh test material formulations.

Results. The vehicle (sterile distilled water) 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.

The test material caused no visible reduction in the growth of the bacterial background lawn at any dose level. The test material was, therefore, tested up to the maximum recommended dose level of 5000 µg/plate. A blue colour was noted from 50 µg/plate, this did not prevent the scoring of revertant colonies. No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix.

No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation.

Conclusion. The test material was considered to be non-mutagenic under the conditions of this test.