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Toxicity to microorganisms

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Description of key information

As the test substance Fluorescein sodium do not have any activity against S. aureus i.e, no difference was observed between the treated test tubes and the control tubes, the NOEC value was found to be 100mg/l.

Key value for chemical safety assessment

EC10, LC10 or NOEC for microorganisms:
100 mg/L

Additional information

Toxicity to micro-organisms study of test chemical Fluorescein sodium was conducted onStaphylococcus aureusof enterotoxigenic strain ATCC 13565.

 

For the preparation of dye solution, a test portion (approximately 10 mg) was placed in a 10-ml volumetric flask, which was wrapped in aluminum foil, and dissolved by adding aqueous sodium hydroxide (approx. 0.4% NaOH) (1 ml) and water (9 ml).

 

Inoculum was prepared inbrain heart infusion broth (BHI). Cultures were incubated shaking (200 rpm) at 37°C. All the experiments were conducted under conditions of standard room illumination (fluorescent ceiling light, Sylvania Octron 4100K) in tubes containing        3 ml of medium. Growth was analyzed by measuring turbidity (absorbance at a wavelength of 660 to 680 nm) with a spectrophotometer (Spectronic 21D). Experiments were initiated with ̴0.2 ml of inoculum from a fresh culture grown aerobically at an optical density (OD) of ̴1. Colony counts were measured on BHI plates.

 

For the study,a 300-µl aliquot of dye solution (1 mg/ml i.e 100 mg/l) was mixed with 0.7 ml of BHI and then added to a tube of diluted culture. The tubes were aerated vigorously, and the OD was measured every 45 min to check culture growth. The survival rate was measured by plating serial dilutions of a sample taken during the experiment on BHI plates.

 

During the study period of 250 mins, OD was measured every 45 mins to check culture growth.

 

Experiment was performed in triplicate on separate days to ascertain reproducibility.

 

As the test substance do not have any activity againstS. aureusi.e, no difference was observed between the treated test tubes and the control tubes, the NOEC value was found to be100 mg/l.

Other supporting study of target chemical(Nepalese Journal of Ophthalmologyl, Vol. 4(7), Pg. no. 80-83, 2012.) indicate that inhibition in growth of test organisms S. aureus,Coagulase negativeStaphylococcus, E. coliandP. aeruginosa,the MIC value was found to be 5000 mg/l.

Thus overall both experimental studies indicate that the test substance Fluorescein sodium is non toxic to micro-organisms.