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Papers by Samaneh Shahrokh

Research paper thumbnail of Toxicity and Unusual Biological Behavior of Nanosilver on Gram Positive and Negative Bacteria Assayed by Microtiter-Plate

The microtiter-plate test is an important indicator for the pathogenicity of bacteria and the mos... more The microtiter-plate test is an important indicator for the pathogenicity of bacteria and the most frequently used techniques for quantifying growth, biofilm formation and respiration assay. The purpose of the present study was to develop a microtiter-plate test, as a quantitative assay, for nanosilver toxicity. It is also superior to the standard microtiter-plate test because it enables indirect measuring of bacteria attached both to the bottom and to the walls of the wells in present of nanosilver. It was surprising that 0.2 ppm of nanosilver promote the formation of biofilm while above this concentration inhibit the biofilm formation by different Gram positive and negative bacteria.

Research paper thumbnail of The Impact of Silver Nanoparticles on Bacterial Aerobic Nitrate Reduction Process

Journal of Bioprocessing & Biotechniques, 2014

Due to the effective antimicrobial properties of silver nanoparticles (Ag NPs), these particles a... more Due to the effective antimicrobial properties of silver nanoparticles (Ag NPs), these particles are receiving an extensive interest for applying in wide range of consumer products and water purification systems. Entering the Ag-based material in wastewater system can influence the biological cycle such as nitrogen. Denitrification as a part of nitrogen cycle is an effective biological process in wastewater systems which can be affected by Ag NPs. The objective of this research was to study the impact of Ag NPs on aerobic nitrate reduction. We showed that Rhizobium sp and Azotobacter sp isolates were able to reduce nitrate aerobically. Adding 0.2 ppm of Ag NPs in culture medium of Azotobacter PHB + enhanced the of the nitrate reduction activity about 20% and Ag NPs at this concentration has no significant effect on the nitrate reduction activity of periplasmic extracts of the selected isolates in aerobic conditions. Thus, entering certain ation of Ag NPs in environments has no significant impact on microbial aerobic denitrification as an important part of nitrogen cycle.

Research paper thumbnail of The enhancement of methyl tertiary butyl ether oxidation by Gordonia in the presence of nanosilver and nitrate

Jundishapur Journal of Microbiology, 2011

... Degradation pathways during the treatment of methyl tert-butyl ether by the UV/H2O2 process. ... more ... Degradation pathways during the treatment of methyl tert-butyl ether by the UV/H2O2 process. Environ Sci Technol. 2000; 34: 650-8. 12) Rai M, Yadav A, Aniket Gade A. Silver nanoparticles as a new generation of antimicrobials. Biotechnol Advances. ...

Research paper thumbnail of Bacterial Profile and Antimicrobial Resistance to Commonly Used Antimicrobials in Intra-Abdominal Infections in Two Teaching Hospitals

American Journal of Applied Sciences, 2010

Problem statement: Intra-abdominal infections are associated with significant morbidity and morta... more Problem statement: Intra-abdominal infections are associated with significant morbidity and mortality. The resulting infection is typically polymicrobial and comprised of both aerobic and anaerobic microbes, which need systemic antimicrobial therapy. Since the bacteriology and antimicrobial susceptibility of postoperative intra abdominal infections were not determined in Iran, so this study was performed to evaluate the antimicrobial susceptibility patterns among aerobic bacteria isolated from post-operative intra-abdominal selected samples in 2 teaching hospitals in Kerman, Iran. Approach: the peritoneal sample of 174 patients which undergone abdominal surgery were cultured by routine microbiological methods for aerobic microorganisms. Antimicrobial susceptibility testing was performed to 4 commonly used antibacterials (Ampicillin, Cefazolin, Gentamicin and Ciprofloxacin) using disc diffusion method according to the NCCLS guidelines. Results: ٍ Escherichia coli (E. coli) was the most frequent microorganism which was isolated from 70.6% of peritoneal cultures, followed by Klebsiella pneumonia (13.7%), Pseudomonas aeruginosa (10.8%) and Proteus mirabilis (4.9%). E. coli which was the most common isolate was highly susceptible to ciprofloxacin (84.6%) and gentamicin (76.9%).The resistance rate of E. coli isolates to ampicillin was very high, i.e, 80.8% of E. coli isolates were resistant to ampicillin. The resistance rate for pseudomonas and Klebsiella spp. to commonly used antimicrobials varied from 25% to ciprofloxacin to 100% to ampicillin. Conclusion: E. coli was the most common isolate in post-operative peritoneal cultures. The results showed the relatively high resistance rate of the isolated microorganisms to commonly used antimicrobials, especially to ampicillin. So the choice of antimicrobial therapy must be based on the susceptibility tests and also take into account the risk of inadequate and in appropriate antimicrobial therapy and emergence of bacterial resistance to commonly used antimicrobials.

Research paper thumbnail of A Comparative Study of the Effects of Colloidal Nanosilver and Industrial Biocide E-265 on Bacterial Respiration and Biofilm Formation Using Microtiterplate Method

nanoparticles have become one of the most commonly used nanomaterials in consumer products becaus... more nanoparticles have become one of the most commonly used nanomaterials in consumer products because of their effective antimicrobial properties and low toxicity toward mammalian cells. In the area of water purification, today nanoparticles are widely used for detection and removal of chemical and biological substances. Therefore by the growing use of nanoparticles, further research is certainly needed to study the behavior of them. In this study, the antibacterial and antibiofilm activities of colloidal nanosilver (average size: 40±10 nm) on the growth, cellular respiration and biofilm formation of pathogenic strains and the isolates from the cooling water of Isfahan Oil Refinery (A1 and A2) were compared with biocide E-265 which generally used in this refinery by microtiterplate method. The results showed that different concentration of biocide E-265 had no significant effects on the bacterial growth and even at 20 and 40 ppm showed 100% increase in the biofilm formation of the isol...

Research paper thumbnail of The Impact of Nano-Silver on Bacterial Aerobic Nitrate Reductase

Journal of Bioprocessing & Biotechniques, 2014

Due to the effective antimicrobial properties of silver nanoparticles (Ag-NPs), these particles a... more Due to the effective antimicrobial properties of silver nanoparticles (Ag-NPs), these particles are receiving an extensive interest for applying in wide range of consumer products and water purification systems. Entering the Agbased material in wastewater system can influence the biological cycle such as nitrogen. Denitrification as a part of nitrogen cycle is an effective biological process in wastewater systems which can be affected by Ag-NPs. The objective of this research was to study the impact of Ag-NPs on aerobic nitrate reduction. We showed that Rhizobium sp and Azotobacter sp isolates were able to reduce nitrate aerobically. Adding 0.2 ppm of Ag-NPs in culture medium of Azotobacter PHB + enhanced the nitrate reduction activity about 20% and Ag-NPs at this concentration has no significant effect on the nitrate reduction activity of periplasmic extracts of the selected isolates in aerobic conditions. Thus, it seems that entering certain concentration of Ag-NPs in environments has no significant impact on microbial aerobic denitrification as a certain part of nitrogen cycle.

Research paper thumbnail of Unusual biological behavior of staphylococci with nano silver assayed by microtiter-plate

2009 9th Ieee Conference on Nanotechnology, Jul 26, 2009

The microtiter-plate test is the most frequently used techniques for quantifying biofilm formatio... more The microtiter-plate test is the most frequently used techniques for quantifying biofilm formation, an important indicator for the pathogenicity of staphylococci. The purpose of the present study was to develop a microtiter-plate test, as a quantitative assay, for nano silver toxicicity. It is also superior to the standard microtiter-plate test because it enables indirect measuring of bacteria attached both to the bottom and to the walls of the wells in present of nano silver. It was surprising that 0.2 ppm of nano silver promote the formation of biofilm while above this concentration inhibit the biofilm formation by Staphylococcus.

Research paper thumbnail of Toxicity and Unusual Biological Behavior of Nanosilver on Gram Positive and Negative Bacteria Assayed by Microtiter-Plate

The microtiter-plate test is an important indicator for the pathogenicity of bacteria and the mos... more The microtiter-plate test is an important indicator for the pathogenicity of bacteria and the most frequently used techniques for quantifying growth, biofilm formation and respiration assay. The purpose of the present study was to develop a microtiter-plate test, as a quantitative assay, for nanosilver toxicity. It is also superior to the standard microtiter-plate test because it enables indirect measuring of bacteria attached both to the bottom and to the walls of the wells in present of nanosilver. It was surprising that 0.2 ppm of nanosilver promote the formation of biofilm while above this concentration inhibit the biofilm formation by different Gram positive and negative bacteria.

Research paper thumbnail of The Impact of Silver Nanoparticles on Bacterial Aerobic Nitrate Reduction Process

Journal of Bioprocessing & Biotechniques, 2014

Due to the effective antimicrobial properties of silver nanoparticles (Ag NPs), these particles a... more Due to the effective antimicrobial properties of silver nanoparticles (Ag NPs), these particles are receiving an extensive interest for applying in wide range of consumer products and water purification systems. Entering the Ag-based material in wastewater system can influence the biological cycle such as nitrogen. Denitrification as a part of nitrogen cycle is an effective biological process in wastewater systems which can be affected by Ag NPs. The objective of this research was to study the impact of Ag NPs on aerobic nitrate reduction. We showed that Rhizobium sp and Azotobacter sp isolates were able to reduce nitrate aerobically. Adding 0.2 ppm of Ag NPs in culture medium of Azotobacter PHB + enhanced the of the nitrate reduction activity about 20% and Ag NPs at this concentration has no significant effect on the nitrate reduction activity of periplasmic extracts of the selected isolates in aerobic conditions. Thus, entering certain ation of Ag NPs in environments has no significant impact on microbial aerobic denitrification as an important part of nitrogen cycle.

Research paper thumbnail of The enhancement of methyl tertiary butyl ether oxidation by Gordonia in the presence of nanosilver and nitrate

Jundishapur Journal of Microbiology, 2011

... Degradation pathways during the treatment of methyl tert-butyl ether by the UV/H2O2 process. ... more ... Degradation pathways during the treatment of methyl tert-butyl ether by the UV/H2O2 process. Environ Sci Technol. 2000; 34: 650-8. 12) Rai M, Yadav A, Aniket Gade A. Silver nanoparticles as a new generation of antimicrobials. Biotechnol Advances. ...

Research paper thumbnail of Bacterial Profile and Antimicrobial Resistance to Commonly Used Antimicrobials in Intra-Abdominal Infections in Two Teaching Hospitals

American Journal of Applied Sciences, 2010

Problem statement: Intra-abdominal infections are associated with significant morbidity and morta... more Problem statement: Intra-abdominal infections are associated with significant morbidity and mortality. The resulting infection is typically polymicrobial and comprised of both aerobic and anaerobic microbes, which need systemic antimicrobial therapy. Since the bacteriology and antimicrobial susceptibility of postoperative intra abdominal infections were not determined in Iran, so this study was performed to evaluate the antimicrobial susceptibility patterns among aerobic bacteria isolated from post-operative intra-abdominal selected samples in 2 teaching hospitals in Kerman, Iran. Approach: the peritoneal sample of 174 patients which undergone abdominal surgery were cultured by routine microbiological methods for aerobic microorganisms. Antimicrobial susceptibility testing was performed to 4 commonly used antibacterials (Ampicillin, Cefazolin, Gentamicin and Ciprofloxacin) using disc diffusion method according to the NCCLS guidelines. Results: ٍ Escherichia coli (E. coli) was the most frequent microorganism which was isolated from 70.6% of peritoneal cultures, followed by Klebsiella pneumonia (13.7%), Pseudomonas aeruginosa (10.8%) and Proteus mirabilis (4.9%). E. coli which was the most common isolate was highly susceptible to ciprofloxacin (84.6%) and gentamicin (76.9%).The resistance rate of E. coli isolates to ampicillin was very high, i.e, 80.8% of E. coli isolates were resistant to ampicillin. The resistance rate for pseudomonas and Klebsiella spp. to commonly used antimicrobials varied from 25% to ciprofloxacin to 100% to ampicillin. Conclusion: E. coli was the most common isolate in post-operative peritoneal cultures. The results showed the relatively high resistance rate of the isolated microorganisms to commonly used antimicrobials, especially to ampicillin. So the choice of antimicrobial therapy must be based on the susceptibility tests and also take into account the risk of inadequate and in appropriate antimicrobial therapy and emergence of bacterial resistance to commonly used antimicrobials.

Research paper thumbnail of A Comparative Study of the Effects of Colloidal Nanosilver and Industrial Biocide E-265 on Bacterial Respiration and Biofilm Formation Using Microtiterplate Method

nanoparticles have become one of the most commonly used nanomaterials in consumer products becaus... more nanoparticles have become one of the most commonly used nanomaterials in consumer products because of their effective antimicrobial properties and low toxicity toward mammalian cells. In the area of water purification, today nanoparticles are widely used for detection and removal of chemical and biological substances. Therefore by the growing use of nanoparticles, further research is certainly needed to study the behavior of them. In this study, the antibacterial and antibiofilm activities of colloidal nanosilver (average size: 40±10 nm) on the growth, cellular respiration and biofilm formation of pathogenic strains and the isolates from the cooling water of Isfahan Oil Refinery (A1 and A2) were compared with biocide E-265 which generally used in this refinery by microtiterplate method. The results showed that different concentration of biocide E-265 had no significant effects on the bacterial growth and even at 20 and 40 ppm showed 100% increase in the biofilm formation of the isol...

Research paper thumbnail of The Impact of Nano-Silver on Bacterial Aerobic Nitrate Reductase

Journal of Bioprocessing & Biotechniques, 2014

Due to the effective antimicrobial properties of silver nanoparticles (Ag-NPs), these particles a... more Due to the effective antimicrobial properties of silver nanoparticles (Ag-NPs), these particles are receiving an extensive interest for applying in wide range of consumer products and water purification systems. Entering the Agbased material in wastewater system can influence the biological cycle such as nitrogen. Denitrification as a part of nitrogen cycle is an effective biological process in wastewater systems which can be affected by Ag-NPs. The objective of this research was to study the impact of Ag-NPs on aerobic nitrate reduction. We showed that Rhizobium sp and Azotobacter sp isolates were able to reduce nitrate aerobically. Adding 0.2 ppm of Ag-NPs in culture medium of Azotobacter PHB + enhanced the nitrate reduction activity about 20% and Ag-NPs at this concentration has no significant effect on the nitrate reduction activity of periplasmic extracts of the selected isolates in aerobic conditions. Thus, it seems that entering certain concentration of Ag-NPs in environments has no significant impact on microbial aerobic denitrification as a certain part of nitrogen cycle.

Research paper thumbnail of Unusual biological behavior of staphylococci with nano silver assayed by microtiter-plate

2009 9th Ieee Conference on Nanotechnology, Jul 26, 2009

The microtiter-plate test is the most frequently used techniques for quantifying biofilm formatio... more The microtiter-plate test is the most frequently used techniques for quantifying biofilm formation, an important indicator for the pathogenicity of staphylococci. The purpose of the present study was to develop a microtiter-plate test, as a quantitative assay, for nano silver toxicicity. It is also superior to the standard microtiter-plate test because it enables indirect measuring of bacteria attached both to the bottom and to the walls of the wells in present of nano silver. It was surprising that 0.2 ppm of nano silver promote the formation of biofilm while above this concentration inhibit the biofilm formation by Staphylococcus.