Fusidic acid

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Remarks:

+ activated sludge nitrification inhibition testing (combined)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

ISO 9509 (Toxicity test for assessing the inhibition of nitrification of activated sludge microorganisms)

Version / remarks:

ISO DIS 9509 (1988)

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: DS 298, (1984)

Version / remarks:

DS 298, (1984)

Deviations:

not specified

GLP compliance:

no

Specific details on test material used for the study:

Test material is sodium salt of fusidic acid.

The degree of dissociation of fusidic acid can be calculated as a function of pH (α = Ka/(Ka+[H+]) with the pKa for fusidic acid determined to be 4.9:
pH α
6.00 0.93
6.50 0.98
7.00 0.99
7.50 1.00
8.00 1.00
For environmental realistic conditions at pH 7-8, fusidic acid will be almost completely (99-100%) dissociated and will be present in the fusidate form. Due to the dissociation of the substance, it is therefore justified to use environmental data on the fusidate form to describe fusidic acid under these conditions.

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

A stock solution of the test substance was prepared in tapwater.
The following concentrations were applied: 0.05, 1.0, 10, 50, 200 mg/L for testing of the inhibition of nitrification of activated sludge from Avedøre Kloakværk A/S.
The following concentrations were applied: 1.0, 10, 50, 200, 500 mg/L for testing of both the inhibition of nitrification and respiration of activated sludge from Frederikssund vandværk and for testing inhibition of respiration of activated sludge from Avedøre Kloakværk A/S.

Test organisms (species):

activated sludge

Details on inoculum:

Activated sludge from: Avedøre Kloakværk A/S and Frederikssund vandværk

Test type:

not specified

Total exposure duration:

3 h

Post exposure observation period:

No

Hardness:

NA

Test temperature:

NA

pH:

NA

Dissolved oxygen:

6 mg/L (nitrification)

Salinity:

NA

Conductivity:

NA

Nominal and measured concentrations:

Applied concentrations: control (no test substance), 0.05, 1, 10, 50, 200 and 500 mg/L

Details on test conditions:

Inhibition of nitrification (ISO/DIS 9505)

Deviations to the guideline were:
- Tap water is applied (with an alkalinity of 6 meq/L) for the nitrification of the added NH4 (25-30 mg NH4-N/L)
- Samples are taken after 10, 90 and 180 min. for determination of NO3-NO2-N and nitrification velocityis determined based on these measurements.
- During the study the test solution is aerated with an air-stone in order to have an oxygen concentration of 6 mg O2/L.
- The test is conducted with duplicates samples

Inhibition of nitrification is determined as the nitrification velocity in % of the control. And the concentration of waste water resulting in an inhibition of 20 % and 50 % respectively, is determined

Sludge applied for the test was recieved from the following sewage treatment plants (STP) Avedøre Kloakværk A/S and Frederikssund renseanlæg.

Inhibition of respiration (DS 298)

Sludge applied for the test was recieved from the following sewage treatment plants (STP) Avedøre Kloakværk A/S and Frederikssund renseanlæg.

Synthetic waste water was applied in order to ensure an optimum amount of organic substance for an optimum respiration.

The test is conducted with duplicates samples

Respiration rate was calculated based on the oxygen consumption during 6 minutes (measured after both 1/2 h and 6 h duration)

Respiration rate was related to the added amount of added sludge measured as suspended solids (SS).

The concentration inhibiting the respiration with 20% and 50% compared to the control (no test substance) was calculated applying the computer program Toxedo

Reference substance (positive control):

no

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 200 mg/L

Conc. based on:

test mat.

Basis for effect:

inhibition of nitrification rate

Remarks on result:

other:

Remarks:

sludge from Avedøre kloakværk A/S

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 500 mg/L

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other:

Remarks:

Sludge from Frederikssund vandværk

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 500 mg/L

Conc. based on:

test mat.

Basis for effect:

inhibition of nitrification rate

Remarks on result:

other:

Remarks:

Sludge from Avedøre kloakværk A/S

Details on results:

Reported EC20 values (95% confidence interval in parenthesis)
EC20 (nitrification, sludge from Avedøre Kloakværk A/S) = 28.9 mg/L (22.1-37.5 mg/L)
EC20 (respiration, sludge from Avedøre Kloakværk A/S) = 238 mg/L (126-470 mg/L)
EC20 (nitrification, sludge from Frederikssund vandværk) > 500 mg/L
EC20 (respiration, sludge from Frederikssund vandværk) ca. 500 mg/L

Results with reference substance (positive control):

NA

Reported statistics and error estimates:

The computerprogram Toxedo was applied for calculating the inhibition of respiration

Validity criteria fulfilled:

not specified

Conclusions:

The inhibition of the test substance on respiration and nitrification was investigated. The following EC20 and EC50 values were obtained (95% confidence interval in parenthesis):
EC20 (nitrification, sludge from Avedøre Kloakværk A/S) = 28.9 mg/L (22.1-37.5 mg/L)
EC20 (respiration, sludge from Avedøre Kloakværk A/S) = 238 mg/L (126-470 mg/L)
EC20 (nitrification, sludge from Frederikssund vandværk) > 500 mg/L
EC20 (respiration, sludge from Frederikssund vandværk) ca. 500 mg/L

EC50 (nitrification, sludge from Avedøre Kloakværk A/S) >200 mg/L
EC50 (respiration, sludge from Avedøre Kloakværk A/S) >500 mg/L
EC50 (nitrification, sludge from Frederikssund vandværk) > 500 mg/L
EC50 (respiration, sludge from Frederikssund vandværk) >500 mg/L

Executive summary:

The inhibition of the test substance (sodium fusidate) on respiration and nitrification was investigated according to guidelines ISO DIS 9509 (1988) and DS 298, (1984).

For environmental realistic conditions at pH 7-8, fusidic acid will be almost completely (99-100%) dissociated and will be present in the fusidate form. Due to the dissociation of the substance, it is therefore justified to use environmental data on the fusidate form to describe fusidic acid under these conditions.

The study was done applying the following fusidin concentration: control (no test substance), 0.05, 1, 10, 50, 200 and 500 mg/L (duplicates) and activated sludge from Avedøre Kloakværk A/S and Frederikssund vandværk.

The following EC20 and EC50 values were obtained:

(95% confidence interval in parenthesis)

EC20 (nitrification, sludge from Avedøre Kloakværk A/S) = 28.9 mg/L (22.1-37.5 mg/L)

EC20 (respiration, sludge from Avedøre Kloakværk A/S) = 238 mg/L (126-470 mg/L)

EC20 (nitrification, sludge from Frederikssund vandværk) > 500 mg/L

EC20 (respiration, sludge from Frederikssund vandværk) ca. 500 mg/L

EC50 (nitrification, sludge from Avedøre Kloakværk A/S) >200 mg/L

EC50 (respiration, sludge from Avedøre Kloakværk A/S) >500 mg/L

EC50 (nitrification, sludge from Frederikssund vandværk) > 500 mg/L

EC50 (respiration, sludge from Frederikssund vandværk) >500 mg/L

Description of key information

The inhibition of sodium fusidate on respiration and nitrification was investigated according to guidelines ISO DIS 9509 (1988) and DS 298, (1984).

For environmental realistic conditions at pH 7-8, fusidic acid will be almost completely (99-100%) dissociated and will be present in the fusidate form. Due to the dissociation of the substance, it is therefore justified to use environmental data on the fusidate form to describe fusidic acid under these conditions.

The study applied the following fusidin concentration: control (no test substance), 0.05, 1, 10, 50, 200 and 500 mg/L (duplicates) and activated sludge from Avedøre Kloakværk A/S and Frederikssund vandværk.

The following EC20 and EC50 values were obtained:

(95% confidence interval in parenthesis)

EC20 (nitrification, sludge from Avedøre Kloakværk A/S) = 28.9 mg/L (22.1-37.5 mg/L)

EC20 (respiration, sludge from Avedøre Kloakværk A/S) = 238 mg/L (126-470 mg/L)

EC20 (nitrification, sludge from Frederikssund vandværk) > 500 mg/L

EC20 (respiration, sludge from Frederikssund vandværk) ca. 500 mg/L

EC50 (nitrification, sludge from Avedøre Kloakværk A/S) >200 mg/L

EC50 (respiration, sludge from Avedøre Kloakværk A/S) >500 mg/L

EC50 (nitrification, sludge from Frederikssund vandværk) > 500 mg/L

EC50 (respiration, sludge from Frederikssund vandværk) >500 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:

500 mg/L

EC10 or NOEC for microorganisms:

28.9 mg/L

Additional information

The lowest toxicity to microorganisms was determined in the study of inhibition of the nitrification of the activated sludge from Avedøre Kloakværk A/S and reported as an EC20 value of 28.9 mg/L.