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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms, other
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Qualifier:
according to
Guideline:
other: Refer below principle
Principles of method if other than guideline:
Antibacterial activity of 20 acetophenone derivatives was evaluated against two Gram-positive and three Gram-negative organisms, namely, Bacillus subtilis NCIM 2718, Staphylococcus aureus NCIM5021, Salmonella typhi NCIM2501, Enterobacter aerogenes NCIM5139, and Proteus vulgaris NCIM2813 by two-fold dilution method.
GLP compliance:
not specified
Specific details on test material used for the study:
- EC name: 3'-nitroacetophenone
- Molecular formula (if other than submission substance): C8H7NO3
- Molecular weight (if other than submission substance): 165.147 g/mol
- Smiles notation (if other than submission substance): c1(cc(ccc1)[N+](=O)[O-])C(C)=O
- InChI: 1S/C8H7NO3/c1-6(10)7-3-2-4-8(5-7)9(11)12/h2-5H,1H3
- Substance type: Organic
- Physical state: Solid
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
other: Bacillus subtilis NCIM 2718;Staphylococcus aureus NCIM5021,Salmonella typhi NCIM2501
Details on inoculum:
Laboratory culture: Bacillus subtilis NCIM 2718 purchased from National Chemical Laboratory, Pune, India
Method of cultivation: Bacteria were cultured in tryptic soy broth medium until the growth reached mid-logarithmic phase).
Preparation of inoculum for exposure: This broth was centrifuged and washed twice with phosphate–urea–magnesium (PUM) buffer containing 17 g K2HPO4, 7.26 g KH2PO4, 1.8 g urea and 0.2 g MgSO4Æ7H2O per litre. The washed cells were resuspended in PUM buffer to reach an OD of 1.0 at 400 nm (OD400).
Test type:
static
Water media type:
freshwater
Total exposure duration:
5 min
Details on test conditions:
Test vessel: Test tubes
Reference substance (positive control):
not specified
Key result
Duration:
5 min
Dose descriptor:
other: MIC
Effect conc.:
3 990 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
other: hydrophilicity
Validity criteria fulfilled:
not specified
Conclusions:
Antibacterial activity of 20 acetophenone derivativeswas evaluated against two Gram-positive and three Gram-negative organisms, namely, Bacillus subtilis NCIM 2718, Staphylococcus aureus NCIM5021, Salmonella typhi NCIM2501, Enterobacter aerogenes NCIM5139, and Proteus vulgaris NCIM2813 by two-fold dilution method.
The Minimum Inhibitory Concentration (MIC) of Bacillus subtilis NCIM 2718 in terms of –log(µM) when exposed to 3 nitroacetophenone is 0.723 which is equivalent to 3990 mg/l.
Executive summary:

Antibacterial activity of 20 acetophenone derivatives was evaluated against two Gram-positive and three Gram-negative organisms, namely, Bacillus subtilis NCIM 2718, Staphylococcus aureus NCIM5021, Salmonella typhi NCIM2501, Enterobacter aerogenes NCIM5139, and Proteus vulgaris NCIM2813 by two-fold dilution method.

 

BATH test is usually performed to determine the hydrophobicity of the bacteria. Bacterial cells have an affinity to hydrocarbons such as hexadecane. The more hydrophobic the bacterial cell, the greater is its affinity to the hydrocarbon, resulting in a transfer of cells from the aqueous suspension to the organic phase, leading to a reduction in the turbidity of the culture in the former. The optical density solution is measured at hexadecane concentrations ranging from 0.0 to 0.2 ml. If the OD (measured at 400 nm) decreases with increasing hexadecane amounts it indicates that the micro-organism is hydrophobic and if a reverse trend is observed then the microorganism is hydrophilic. Decreasing OD indicates that more of the cells are moving to the hydrophobic hexadecane. Bacteria were cultured in tryptic soy broth medium until the growth reached mid-logarithmic phase. This broth was centrifuged and washed twice with phosphate–urea–magnesium (PUM) buffer containing 17 g K2HPO4, 7.26 g KH2PO4, 1.8 g urea and 0.2 g MgSO4.7H2O per litre. The washed cells were re-suspended in PUM buffer to reach an OD of 1.0 at 400 nm (OD400). Aliquots of 1.0 ml of this suspension were transferred to a set of test tubes, to which increasing volumes (ranging from 0–0.2 ml in steps of 0.05 ml) of hexadecane were added. The test tubes were shaken for 10 min and allowed to stand for 2 min to facilitate the phase separation. The OD of the aqueous suspension was measured at 400 nm, while cell-free buffer served as the blank. 

The Minimum Inhibitory Concentration (MIC) of Bacillus subtilis NCIM 2718 in terms of -log(µM) when exposed to 3 nitroacetophenone is 0.723 which is equivalent to 3990 mg/l.

Description of key information

Antibacterial activity of 20 acetophenone derivatives was evaluated against two Gram-positive and three Gram-negative organisms, namely, Bacillus subtilis NCIM 2718, Staphylococcus aureus NCIM5021, Salmonella typhi NCIM2501, Enterobacter aerogenes NCIM5139, and Proteus vulgaris NCIM2813 by two-fold dilution method.

 

BATH test is usually performed to determine the hydrophobicity of the bacteria. Bacterial cells have an affinity to hydrocarbons such as hexadecane. The more hydrophobic the bacterial cell, the greater is its affinity to the hydrocarbon, resulting in a transfer of cells from the aqueous suspension to the organic phase, leading to a reduction in the turbidity of the culture in the former. The optical density solution is measured at hexadecane concentrations ranging from 0.0 to 0.2 ml. If the OD (measured at 400 nm) decreases with increasing hexadecane amounts it indicates that the micro-organism is hydrophobic and if a reverse trend is observed then the microorganism is hydrophilic. Decreasing OD indicates that more of the cells are moving to the hydrophobic hexadecane. Bacteria were cultured in tryptic soy broth medium until the growth reached mid-logarithmic phase. This broth was centrifuged and washed twice with phosphate–urea–magnesium (PUM) buffer containing 17 g K2HPO4, 7.26 g KH2PO4, 1.8 g urea and 0.2 g MgSO4.7H2O per litre. The washed cells were re-suspended in PUM buffer to reach an OD of 1.0 at 400 nm (OD400). Aliquots of 1.0 ml of this suspension were transferred to a set of test tubes, to which increasing volumes (ranging from 0–0.2 ml in steps of 0.05 ml) of hexadecane were added. The test tubes were shaken for 10 min and allowed to stand for 2 min to facilitate the phase separation. The OD of the aqueous suspension was measured at 400 nm, while cell-free buffer served as the blank.

 

The Minimum Inhibitory Concentration (MIC) of Bacillus subtilis NCIM 2718 in terms of -log(µM) when exposed to 3 nitroacetophenone is 0.723 which is equivalent to 3990 mg/l.

Key value for chemical safety assessment

Additional information

Three studies including two experimental data and one predicted result from validated prediction for endpoint toxicity to micro organisms to target chemical 3'-nitroacetophenone(Cas no. 121-89-1) with relevant read across substance which is close to target using log kow as primary descriptor were summarized as followed:

First study of target available from experimental data source (Chem Biol Drug Des 2008; 72: 303–313; 2008) which indicate the antibacterial activity of 20 acetophenone derivatives was evaluated against two Gram-positive and three Gram-negative organisms, namely, Bacillus subtilis NCIM 2718, Staphylococcus aureus NCIM5021, Salmonella typhi NCIM2501, Enterobacter aerogenes NCIM5139, and Proteus vulgaris NCIM2813 by two-fold dilution method.BATH test is usually performed to determine the hydrophobicity of the bacteria. Bacterial cells have an affinity to hydrocarbons such as hexadecane. The more hydrophobic the bacterial cell, the greater is its affinity to the hydrocarbon, resulting in a transfer of cells from the aqueous suspension to the organic phase, leading to a reduction in the turbidity of the culture in the former. The optical density solution is measured at hexadecane concentrations ranging from 0.0 to 0.2 ml. If the OD (measured at 400 nm) decreases with increasing hexadecane amounts it indicates that the micro-organism is hydrophobic and if a reverse trend is observed then the microorganism is hydrophilic. Decreasing OD indicates that more of the cells are moving to the hydrophobic hexadecane. Bacteria were cultured in tryptic soy broth medium until the growth reached mid-logarithmic phase. This broth was centrifuged and washed twice with phosphate–urea–magnesium (PUM) buffer containing 17 g K2HPO4, 7.26 g KH2PO4, 1.8 g urea and 0.2 g MgSO4.7H2O per litre. The washed cells were re-suspended in PUM buffer to reach an OD of 1.0 at 400 nm (OD400). Aliquots of 1.0 ml of this suspension were transferred to a set of test tubes, to which increasing volumes (ranging from 0–0.2 ml in steps of 0.05 ml) of hexadecane were added. The test tubes were shaken for 10 min and allowed to stand for 2 min to facilitate the phase separation. The OD of the aqueous suspension was measured at 400 nm, while cell-free buffer served as the blank.The Minimum Inhibitory Concentration (MIC) of Bacillus subtilis NCIM 2718 in terms of -log(µM) when exposed to 3 nitroacetophenone is 0.723 which is equivalent to 3990 mg/l.

And the toxicity to micro organism of the substance 3'-nitroacetophenoneto micro organism is predicted using QSAR toolbox version.3.4, based on the effects observed in a static freshwater system during a 48 hr exposure. The Inhibition growth concentration (IGC50) for the substance3'-nitroacetophenoneis estimated to be 236.51 mg/L. Based on this value, it can be concluded that the test chemical 3'-nitroacetophenonemay have no concern to micro organism toxicity for acute exposure.

Whereas read across chemical 4-Benzoylpyridine (CAS no.14548-46-0) from experimental result indicate twenty-two four-position derivatives of pyridine (CS5H5N) including chemical 4-Benzoylpyridine (Cas no. 14548-46-0) were tested following an acute static regime with biological response being monitored as population growth of Tetrahymena pyriformis. Stock solution was prepared in 50 g/liter vehicle DMSO. The amicronucleated strain GL-C of the common freshwater ciliate Tetrahymena pyriformis was reared in axenic culture at 28°C in a semi defined medium (Schultz et al., 1980). Test chemical was assayed in duplicate for a minimum of three replicates using a five-step graded concentration series. Each replicate was assayed with freshly prepared stock solutions and flasks without test chemicals were used as controls. And Population growth determinations were done using probit analysis in the Statistical Analysis System (SAS) software which suggest that effect concentration (EC50) for the substance 4-Benzoylpyridine (CAS no.14548-46-0) was determine to be 227.02 mg/l on micro organism Tetrahymena pyriformis on the basis of population effect in static fresh water for 60 hrs.exposure period with 95 % confidence limit of 164.13 - 566.45.

Thus all available information for micro organism toxicity interpreted the common conclusion that the target chemical 3'-nitroacetophenone (Cas no. 121-89-1) may not have concern for toxicity to micro organism for acute exposure period.