Registration Dossier

Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
21 June 2017 - 09 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
Report Date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
1997
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Details on test material:
Test Item: Leuco Sulfur Blue 15
Appearance: Dark, near black powder

Method

Target gene:
In addition to histidine and tryptophan mutation, each strain has additional mutations which enhance its sensitivity to mutagens. The uvrB (uvrA) strains are defective in excision repair. It causes the strains to be more sensitive to the mutagenic and lethal effects of a wide variety of mutagens because they cannot repair DNA damages. The rfa mutation increases the permeability of the bacterial lipopolysaccharide wall for larger molecules. The plasmid pKM101 (TA98, TA100) carries the muc+ gene which participates in the error-prone "SOS" DNA repair pathway induced by DNA damage. This plasmid also carries an ampicillin resistance transfer factor (R-factor) which is used to identify its presence in the cell. The Escherichia coli strain used in this test (WP2 uvrA) is also defective in DNA excision repair.
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:
post mitochondrial supernatant (S9) prepared from livers of Phenobarbital/β-naphthoflavone-induced rats
Test concentrations with justification for top dose:
5000; 1600; 500; 160; 50 and 16 µg/plate
Vehicle / solvent:
dimethyl sulfoxide (DMSO)
Controls
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
sodium azide
methylmethanesulfonate
other: 4-Nitro-1,2-phenylenediamine, 2-aminoanthracene
Details on test system and experimental conditions:
Origin of the Bacterial Strains

Tester strains: Salmonella typhimurium TA98, TA100, TA1535, TA1537 and Escherichia coli WP2 uvrA were obtained from:
Supplier: Trinova Biochem GmbH; Rathenau Str. 2; D-35394 Giessen, Germany;
Manufacturer: MOLTOX INC., P.O. BOX 1189; BOONE, NC 28607 USA.
Frozen stock cultures were prepared from the disc cultures.

Storage of Tester Strains

The strains are stored at -80 ± 10 ºC in the Laboratory of TOXI-COOP ZRT. in the form of lyophilized discs and in frozen permanent copies. Frozen permanent cultures of the tester strains are prepared from fresh, overnight cultures to which DMSO (8 % (v/v)) is added as a cryoprotective agent.

Confirmation of Phenotypes of Tester Strains

The phenotypes of the tester strains used in the bacterial reverse mutation assays with regard to membrane permeability (rfa), UV sensitivity (uvrA and uvrB), ampicillin resistance (amp), as well as spontaneous mutation frequencies are checked regularly.

Spontaneous Reversion of Tester Strains

Each tester strain reverts spontaneously at a frequency that is characteristic for the strain. Spontaneous reversions of the test strains to histidine or tryptophan prototrophs are measured routinely in mutagenicity experiments and expressed as the number of spontaneous revertants per plate.

Procedure for Bacterial Cultures

The frozen bacterial cultures were thawed at room temperature and 200 µL inoculum was used to inoculate each 50 mL of Nutrient Broth No. 2 for the overnight cultures in the assay. The cultures were incubated for approximately 10-13 hours in a 37 °C Benchtop Incubator Shaker.

The viability of each testing culture was determined by plating 0.1 mL of the 10-5, 10-6, 10-7 and 10-8 dilutions of cultures on nutrient agar plates. The viable cell number of the cultures was determined by manual colony counting.

Metabolic Activation System

The test bacteria were also exposed to the test item in the presence of an appropriate metabolic activation system, which is a cofactor-supplemented post-mitochondrial fraction (S9).

Rat Liver S9 Fraction

The S9 fraction of phenobarbital (PB) and β-naphthoflavone (BNF)-induced rat liver was provided by Trinova Biochem GmbH (Rathenau Str. 2; D-35394 Giessen, Germany; Manufacturer: MOLTOX INC., P.O. BOX 1189; BOONE, NC 28607 USA).
Rationale for test conditions:
Justification of concentrations:
Selection of the concentration range was done on the basis of solubility tests and concentration range finding test (informatory toxicity test).
Based on the solubility test, a stock suspension with a concentration of 50 mg/mL was prepared in dimethyl sulfoxide (DMSO) and further diluted accordingly.
In the informatory toxicity test a correction factor, based on the active component of the test item (88.66 %) was taken into consideration.
The revertant colony numbers and the inhibition of the background lawn of auxotrophic cells of two of the tester strains (Salmonella typhimurium TA98, TA100) were determined at the concentrations of 5000, 1600, 500, 160, 50, 16 and 5 µg/plate of the test item.
In the informatory toxicity test the revertant colony numbers of solvent control plates with and without S9 mix were in line with the corresponding historical control data ranges. The positive control treatments showed the expected biological relevant increases in induced revertant colonies in both tester strains.

Evaluation criteria:
A test item is considered mutagenic if:
- a dose–related increase in the number of revertants occurs and/or;
- a reproducible biologically relevant positive response for at least one of the dose groups occurs in at least one strain with or without metabolic activation.
An increase is considered biologically relevant if:
- in strain Salmonella typhimurium TA100 the number of reversions is at least twice as high as the reversion rate of the solvent control,
- in strain Salmonella typhimurium TA98, TA1535, TA1537 and Escherichia coli WP2 uvrA the number of reversions is at least three times higher than the reversion rate of the solvent control.

Criteria for a negative response:
A test item is considered non-mutagenic if it produces neither a dose-related increase in the number of revertants nor a reproducible biologically relevant positive response at any of the dose groups, with or without metabolic activation.
Statistics:
According to the guidelines, the biological relevance of the results is the criterion for the interpretation of results, a statistical evaluation of the results is not regarded as necessary. The mean values and appropriate standard deviations and mutation rates were calculated by EXCEL software.

Results and discussion

Test resultsopen allclose all
Key result
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Key result
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not examined
Positive controls validity:
valid
Additional information on results:
The tester strains used in this study demonstrated the specific phenotype characteristics, were in line with the corresponding historical control data ranges, and showed the adequate strain culture titer.
Each batch of the S9 fraction used in this test had the appropriate biological activity and was active in the applied system.
Each of the investigated reference mutagens showed the expected increase (at least a 3-fold increase) in induced revertant colonies over the mean value of the respective solvent control in all main experimental phases and the number of revertants in most cases fell in the corresponding historical control ranges, thereby meeting the criteria for the positive control in the main experimental phases, in both tester strains.
The spontaneous revertant colony numbers of the dimethyl sulfoxide (DMSO) solvent control plates showed characteristic mean numbers agreed with the actual historical control data ranges in all strains in both main experimental phases.
Six concentration levels were investigated in the main mutation experiments (initial and confirmatory mutation tests).
In the performed main experimental phases there were at least five analyzable concentrations and a minimum of three non-toxic and non-precipitated dose levels at each tester strain.
All criteria for the validity of the performed experiments have therefore been met.

Controls:
In the performed initial and confirmatory mutation test multiple test items were tested with reference values from the common parallel controls.
In the initial and confirmatory mutation tests the revertant colony numbers of the dimethyl sulfoxide (DMSO) solvent control plates with and without S9 mix were in line with the corresponding historical control data ranges.
The reference mutagen treatments (positive controls) showed the expected, biological relevant increases in induced revertant colonies in all experimental phases, in all tester strains. In the Confirmatory Mutation Test, in the case of Escherichia coli WP2 uvrA the revertant colony numbers of Methyl methanesulfonate (MMS) were above the corresponding historical control data range; however the higher counts were considered as acceptable without any effect on the final conclusion of the study.
The revertant colony numbers of the untreated and ultrapure water control plates in different experimental phases were slightly higher or lower than the DMSO control plates. The higher or lower revertant counts of these controls remained in the corresponding historical control data ranges.
In summary, the actual values of untreated, solvent and positive controls were in line with the criteria for validity of the assay.

Initial and Confirmatory Mutation Tests (Plate Incorporation Test and Pre-Incubation Test):
No substantial increases were observed in revertant colony numbers of any of the five test strains following treatment with the test item at any concentration level, either in the presence or absence of metabolic activation (S9 mix) in the performed experiments.
In the performed experiments, sporadically increased revertant colony numbers were observed. These increases did not show a clear dose-response relationship, were mostly of minor intensity, and all of the increases remained far below the biologically relevant thresholds for being positive. The obtained increases were therefore considered as biologically not relevant, being in the range of the biological variability of the applied test system.
The highest revertant colony number increase was observed in the confirmatory mutation test (pre-incubation test) in S. typhimurium TA98 strain, at 16 μg/plate, in the absence of metabolic activation (S9 mix). The revertant colony numbers at this treatment remained within the corresponding solvent historical control data range; furthermore the higher value was unique and additional clear concentration related increase in revertant colony counts was not noticed. The mutation rate was 2.18, which was far below the genotoxicological threshold for being positive.
In the initial and confirmatory mutation tests, an unequivocal inhibitory effect of the test item on bacterial growth was observed. In the initial mutation test inhibitory effect of the test item was observed in the S. typhimurium TA1537 strain only, in the absence of exogenous metabolic activation. In the confirmatory mutation test an inhibitory, cytotoxic effect of the test item was noticed in all examined strains. The inhibitory, cytotoxic effect of the test item manifested stronger in absence of exogenous metabolic activation (S9 mix). The cytotoxicity was indicated by decreased revertant colony counts (often below the corresponding historical control data ranges) and/or affected background lawn development: reduced or slightly reduced background lawn. All of the further observed lower revertant colony numbers (when compared to the revertant colony numbers of the corresponding solvent control) remained in the range of the biological variability of the applied test system.In general, 500 µg/plate was considered as lowest concentration showing cytotoxicity.
When evaluated by naked eye, non-interfering test item precipitate was noticed after about 48 hours incubation on the plates in the examined strains at the concentrations of 5000 and 1600 µg/plate in the absence and also in the presence of exogenous metabolic activation following the plate incorporation procedure, in the concentration range of 5000-500 µg/plate in absence of S9 and at the concentrations of 5000 and 1600 µg/plate in the presence of S9 following the pre-incubation procedures.

Any other information on results incl. tables

Summary of the Inhibitory Tendencies in the Initial and Confirmatory Mutation Tests

Initial Mutation Test

Concentrations

(µg/plate)

Salmonella typhimurium

Escherichia coliWP2uvrA

TA98

TA100

TA1535

TA1537

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

5000

-

-

-

-

-

-

< SB

-

-

-

1600

-

-

-

-

-

-

SB*

-

-

-

500

-

-

-

-

-

-

-

-

-

-

160

-

-

-

-

-

-

-

-

-

-

50

-

-

-

-

-

-

-

-

-

-

16

-

-

-

-

-

-

-

-

-

-

Confirmatory Mutation Test

Concentrations

(µg/plate)

Salmonella typhimurium

Escherichia coliWP2uvrA

TA98

TA100

TA1535

TA1537

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

5000

SB

<< 

SB*

<< 

< B

<< B

< B

1600

SB

-

<< SB

-

< B

-

< SB

< SB

-

-

500

<< SB

-

<< SB

-

SB

-

SB*

SB*

-

-

160

-

-

-

-

-

-

-

-

-

-

50

-

-

-

-

-

-

-

-

-

-

16

-

-

-

-

-

-

-

-

-

-

<:         Revertant colony numbers significantly (MR ≤ 0.6) below the solvent control data range

<<:      Revertant colony numbers below the solvent and historical control data ranges

~:          Slight equivocal test item effect

B:         Reduced background lawn development

SB:       Slightly reduced background lawn development

SB*:      Revertant colony numbers within or above the actual solvent control data range; however slightly reduced background lawn development

Summary Table of the Results of the Concentration Range Finding Test

Concentration Range Finding Test (Informatory Toxicity Test)

 

Concentrations (mg/plate)

Salmonella typhimuriumtester strains

TA 98

TA 100

-S9

+S9

-S9

+S9

Mean values of revertants per plate and
Mutation rate (MR)

Mean

MR

Mean

MR

Mean

MR

Mean

MR

 

Untreated Control

19.7

1.13

23.0

1.08

97.3

1.13

125.3

1.27

 

DMSO Control   

17.3

1.00

21.3

1.00

86.3

1.00

98.7

1.00

 

Ultrapure Water Control 

92.0

1.00

 

5000

16.3

0.94

20.0

0.94

88.0

1.02

92.7

0.94

 

1600

20.0

1.15

16.3

0.77

92.3

1.07

95.3

0.97

 

500

21.0

1.21

18.0

0.84

86.3

1.00

89.7

0.91

 

160

16.3

0.94

13.7

0.64

87.0

1.01

90.0

0.91

 

50

18.0

1.04

19.7

0.92

90.0

1.04

92.7

0.94

 

16

22.0

1.27

16.0

0.75

107.7

1.25

93.3

0.95

 

5

22.0

1.27

18.7

0.88

91.0

1.05

105.7

1.07

 

NPD (4mg)

367.0

21.17

 

SAZ (2mg)

1221.3

13.28

 

2AA (2mg)

2122.7

99.50

2445.3

24.78

 

MR:Mutation Rate

NPD:4-Nitro-1,2-phenylenediamine

SAZ:Sodium azide

2AA:2-aminoanthracene

Remarks:   DMSO was applied as solvent of the test item and positive control substances: NPD and 2AA and the ultrapure water was applied as solvent for the SAZ. The mutation rate of the test item, the untreated control the NPD and 2AA is given referring to the DMSO. The mutation rate of the SAZ positive control is given referring to the ultrapure water.

 

Summary Table of the Results of the Initial Mutation Test

Initial Mutation Test (Plate Incorporation Test)

Concentrations (mg/plate)

Salmonella typhimuriumtester strains

Escherichiacoli

TA 98

TA 100

TA 1535

TA 1537

WP2 uvrA

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

Mean values of revertants per plate Mutation rate (MR)

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Untreated Control

21.0

0.93

26.0

1.07

93.7

1.30

96.7

1.09

8.3

0.78

11.3

1.31

7.0

0.84

8.3

1.04

26.7

1.25

25.7

0.74

DMSO Control

22.7

1.00

24.3

1.00

72.0

1.00

88.3

1.00

10.7

1.00

8.7

1.00

8.3

1.00

8.0

1.00

21.3

1.00

34.7

1.00

Ultrapure Water Control

89.0

1.00

9.3

1.00

26.7

1.00

5000

17.0

0.75

18.7

0.77

65.7

0.91

74.3

0.84

10.3

0.97

7.7

0.88

4.0

0.48

7.7

0.96

20.7

0.97

24.0

0.69

1600

20.3

0.90

25.0

1.03

66.7

0.93

74.0

0.84

8.3

0.78

10.7

1.23

7.3

0.88

6.7

0.83

28.0

1.31

29.3

0.85

500

21.0

0.93

27.3

1.12

66.0

0.92

78.0

0.88

8.7

0.81

10.0

1.15

8.0

0.96

8.7

1.08

27.0

1.27

30.0

0.87

160

16.7

0.74

26.0

1.07

65.0

0.90

84.3

0.95

14.3

1.34

10.3

1.19

7.7

0.92

9.3

1.17

27.0

1.27

24.3

0.70

50

22.7

1.00

21.7

0.89

67.7

0.94

80.3

0.91

10.3

0.97

11.0

1.27

7.7

0.92

8.7

1.08

26.7

1.25

35.3

1.02

16

20.7

0.91

23.7

0.97

67.3

0.94

74.0

0.84

13.7

1.28

10.7

1.23

8.3

1.00

6.3

0.79

20.7

0.97

32.3

0.93

NPD (4mg)

306.0

13.50

SAZ (2mg)

988.0

11.10

1428.0

153.00

9AA (50mg)

209.0

25.08

MMS (2mL)

810.7

30.40

2AA (2mg)

1957.3

80.44

1001.3

11.34

222.3

25.65

191.3

23.92

2AA (50mg)

202.0

5.83

MR: Mutation Rate; NPD: 4-Nitro-1,2-phenylenediamine; SAZ: Sodium azide; 9AA: 9-Aminoacridine; MMS: Methyl methanesulfonate; 2AA: 2-aminoanthracene

Remarks: DMSO was applied as solvent of the test item and positive control substances: NPD, 9AA and 2AA and the ultrapure water was applied as solvent for the SAZ and MMS. The mutation rate of the test item and the untreated control is given referring to the DMSO. The mutation rate of the NPD, 9AA and 2AA is given referring to the DMSO and the mutation rate of the SAZ and MMS positive control is given referring to the ultrapure water.

Summary Table of the Results of the Confirmatory Mutation Test

Confirmatory Mutation Test (Pre-Incubation Test)

Concentrations (mg/plate)

Salmonella typhimuriumtester strains

Escherichia coli

TA 98

TA 100

TA 1535

TA 1537

WP2 uvrA

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

Mean values of revertants per plate Mutation rate (MR)

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Mean

MR

Untreated Control

18.3

1.25

20.7

1.03

82.7

1.11

102.3

1.11

15.0

0.82

12.3

0.84

7.0

1.17

9.0

1.04

29.3

1.00

32.7

0.88

DMSO Control

14.7

1.00

20.0

1.00

74.3

1.00

92.0

1.00

18.3

1.00

14.7

1.00

6.0

1.00

8.7

1.00

29.3

1.00

37.3

1.00

Ultrapure Water Control

77.7

1.00

14.3

1.00

39.3

1.00

5000

10.3

0.70

13.3

0.67

67.3

0.91

69.3

0.75

8.3

0.45

8.3

0.57

1.0

0.17

4.7

0.54

17.3

0.59

24.0

0.64

1600

9.7

0.66

14.7

0.73

40.3

0.54

77.3

0.84

2.7

0.15

10.7

0.73

1.7

0.28

3.3

0.38

21.7

0.74

34.0

0.91

500

8.3

0.57

20.7

1.03

42.0

0.57

82.7

0.90

14.3

0.78

11.7

0.80

9.0

1.50

7.0

0.81

27.0

0.92

31.3

0.84

160

16.0

1.09

16.3

0.82

74.3

1.00

85.3

0.93

15.3

0.84

15.0

1.02

7.0

1.17

7.7

0.88

27.0

0.92

35.3

0.95

50

14.0

0.95

22.3

1.12

88.7

1.19

96.0

1.04

12.7

0.69

12.3

0.84

9.0

1.50

9.0

1.04

26.0

0.89

33.3

0.89

16

32.0

2.18

18.0

0.90

94.3

1.27

82.0

0.89

14.7

0.80

14.0

0.95

5.0

0.83

11.3

1.31

21.7

0.74

34.0

0.91

NPD (4mg)

304.0

20.73

SAZ (2mg)

981.3

12.64

978.7

68.28

9AA (50mg)

738.7

123.11

MMS (2mL)

1544.0

39.25

2AA (2mg)

1411.3

70.57

2442.7

26.55

234.0

15.95

209.7

24.19

2AA (50mg)

249.7

6.69

MR: Mutation Rate; NPD:4 -Nitro-1,2-phenylenediamine; SAZ: Sodium azide; 9AA: 9 -Aminoacridine; MMS: Methyl methanesulfonate; 2AA: 2-aminoanthracene

Remarks: DMSO was applied as solvent of the test item and positive control substances: NPD, 9AA and 2AA and the ultrapure water was applied as solvent for the SAZ and MMS. The mutation rate of the test item and the untreated control is given referring to the DMSO. The mutation rate of the NPD, 9AA and 2AA is given referring to the DMSO and the mutation rate of the SAZ and MMS positive control is given referring to the ultrapure water.

Historical Control Values for Revertants/Plate (for the Period of 2008-2016)

 

Bacterial strains

Historical control data of untreated control

‑S9

 

TA98

TA100

TA1535

TA1537

E. coli

Average

21.0

105.0

10.5

8.1

25.4

SD

3.7

25.7

1.4

2.3

5.2

Minimum

9

66

3

2

11

Maximum

39

155

23

19

45

n

226

236

216

214

215

+S9

 

TA98

TA100

TA1535

TA1537

E. coli

Average

27.5

117.1

11.8

9.0

33.9

SD

4.3

18.1

1.4

1.9

5.2

Minimum

12

75

4

2

17

Maximum

46

166

23

20

56

n

226

236

216

214

215

 

Bacterial strains

Historical control data of DMSO

control

‑S9

 

TA98

TA100

TA1535

TA1537

E. coli

Average

20.4

100.1

10.3

7.9

24.7

SD

3.6

24.8

1.3

2.4

4.6

Minimum

10

64

3

2

11

Maximum

38

147

23

20

45

n

226

236

216

214

215

+S9

 

TA98

TA100

TA1535

TA1537

E. coli

Average

26.5

113.8

11.8

8.8

33.7

SD

4.1

18.3

1.5

1.9

5.0

Minimum

15

71

3

3

16

Maximum

47

162

25

20

57

n

226

236

216

214

215

 

Bacterial strains

Historical control data of Water

control

‑S9

 

TA98

TA100

TA1535

TA1537

E. coli

Average

21.9

104.7

10.5

7.6

26.1

SD

3.7

25.9

1.5

2.2

5.5

Minimum

12

68

3

2

12

Maximum

35

154

24

16

48

n

89

236

216

89

215

+S9

 

TA98

TA100

TA1535

TA1537

E. coli

Average

27.4

117.3

11.4

8.7

34.9

SD

4.0

18.5

1.3

2.2

4.9

Minimum

15

83

4

3

18

Maximum

43

167

22

16

57

n

89

152

149

89

148

Abbreviations:   TA98, TA100, TA1535, TA1537: Salmonella typhimuriumTA98, TA100, TA1535,

                               TA1537; E. coli:Escherichia coliWP2uvrA

                                               SD: Standard deviation;    DMSO: Dimethyl sulfoxide;n: number of studies


Historical Control Values for Revertants/Plate (for the Period of 2008-2016) (continued)

 

Bacterial strains

Historical control data of positive controls

‑S9

 

TA98

TA100

TA1535

TA1537

E. coli

Average

260.1

977.2

847.3

478.6

724.5

SD

31.8

150.6

126.3

104.5

65.0

Minimum

123

521

359

110

320

Maximum

664

1970

1855

1601

1313

n

226

236

216

214

215

+S9

 

TA98

TA100

TA1535

TA1537

E. coli

Average

1222.7

1436.4

164.1

147.0

257.7

SD

274.9

318.3

33.1

20.1

72.5

Minimum

386

583

85

69

140

Maximum

2676

2988

498

399

477

n

226

236

216

214

215

Abbreviations:   TA98, TA100, TA1535, TA1537: Salmonella typhimuriumTA98, TA100, TA1535,

                               TA1537;E. coli:Escherichia coliWP2uvrA

                                     SD: Standard deviation;   DMSO: Dimethyl sulfoxide;  n: number of studies

Applicant's summary and conclusion

Conclusions:
The test item has no mutagenic activity on the applied bacterium tester strains under the test conditions used in this study.
Executive summary:

The test item was tested with regard to a potential mutagenic activity using the Bacterial Reverse Mutation Assay according to OECD guideline 471. The experiments were carried out using histidine-requiring auxotroph strains of Salmonella typhimurium (Salmonella typhimuriumTA98, TA100, TA1535 and TA1537), and the tryptophan-requiring auxotroph strain of Escherichia coli (Escherichia coliWP2uvrA) in the presence and absence of a post mitochondrial supernatant (S9) prepared from livers of Phenobarbital/b-naphthoflavone-induced rats. The study included preliminary solubility tests, preliminary concentration range finding test (informatory toxicity test), an initial mutation test (plate incorporation test), and a confirmatory mutation test (pre-incubation test). Based on the results of the solubility test and the concentration range finding test the test item was dissolved in dimethyl sulfoxide (DMSO). At the formulation of test item solutions correction of concentrations for active component content (88.66 %) was made in the experiments. Based on the results of the preliminary concentration range finding test (informatory toxicity test) the following concentrations of the test item were prepared and investigated in the initial and confirmatory mutation tests: 5000; 1600; 500; 160; 50 and 16 µg/plate. The selection of the concentration range was based on the recommendations in OECD 471 guideline. At the concentration choice the non-toxicity of the test item and the precipitation of the test item in the final treatment mixture were taken into consideration. The observations were made by naked eye. When evaluated by naked eye, non-interfering test item precipitate was noticed after about 48 hours incubation on the plates in the examined strains at the concentrations of 5000 and 1600 µg/plate in the absence and also in the presence of exogenous metabolic activation following the plate incorporation procedure, in the concentration range of 5000-500 µg/plate in absence of S9 and at the concentrations of 5000 and 1600 µg/plate in the presence of S9 following the pre-incubation procedures. An inhibitory effect of the test item was observed in the initial mutation test in the S. typhimurium TA1537 strain in absence of S9, in the confirmatory mutation test in all tested strains in the absence and presence of exogenous metabolic activation. The inhibitory effect was indicated by decreased revertant colony counts (some of them below the corresponding historical control data ranges) and/or affected background lawn development: reduced or slightly reduced background lawn. In general, 500 µg/plate (in all tested S. typhimurium strains) was considered as lowest concentration showing cytotoxicity. The revertant colony numbers of solvent control (DMSO) plates with and without S9 mix demonstrated the characteristic mean number of spontaneous revertants that was in line with the corresponding historical control data ranges. The reference mutagen treatments (positive controls) showed the expected biologically relevant increases (more than 3-fold increase)in induced revertant colonies and the number of revertants fell mostly in the corresponding historical control ranges, thereby meeting the criteria for the positive control in all experimental phases, in all tester strains. No biologically relevant increases were observed in revertant colony numbers of any of the five test strains following treatment with the test item at any concentration level, either in the presence or absence of metabolic activation (S9 mix) in the performed experiments. The reported data of this mutagenicity assay show that under the experimental conditions applied, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used. In conclusion, the test item has no mutagenic activity on the applied bacterium tester strains under the test conditions used in this study.