الفهرس 
Literature ofReviewOnly 14 pages are availabe for public view
 |  | from | 235 |  |  |
| | | from | 235 | | |
Abstract
This work involved the study of the ability of different bacteria isolated from gold and silver-rich dust from jewelry workshops in jewish quarter, El Sagha, Egypt to synthesize gold and silver nanoparticles outside the cell and the factors that affect the biosynthesis of both gold and silver nanoparticles, also, study the effect of these nanoparticles against multidrug resistant pathogenic strains, Comparing antimicrobial efficiency of different antibiotics with AuNPs and AgNPs and the main objective of this study was concentrated on the effect of Combination between non-effective antibiotics and AuNPs or AgNPs against multidrug resistant pathogenic strains.
Three out of twenty examined bacterial isolates were selected to produce AuNPs. The MAM-S20 bacterial isolate was the most potent isolate for AuNPs production outside the cell and was identified by 16SrRNA asProvidenicavermicola with 98% similarity with Providenicavermicola strain OP1. with accession No. MN900605.1.
The optimum conditions for the production of AuNPs were chosen as the salt concentration in the solution (2 mM) at pH 8.0 and 40 °C for 2 hours. It gives the maximum SPR was given at 540 nm. The average size of the particles was (18.02 nm). The average zeta size was (124.4 nm).
While, seven out of twenty examined bacterial isolates were selected to produce AgNPs. The MAM-S17 bacterial isolate was the most potent isolate for AgNPs production outside the cell and was identified by 16SrRNA as Lysinibacillusfusiformis with 99% similarity of Lysinibacillusfusiformis NBRC15717.under accession No.900609.1.
The optimum conditions for the production of AgNPs were recorded as the salt concentration in the solution (2.5 mM) at pH 7.0 and 40 °C for 2 hours. It gives the maximum SPR was given at 430 nm. The smaller average size of the particles was (4.0 nm). The average zeta size was (56.75 nm).
In the present study, the antimicrobial activity of the synthesized AuNPs and AgNPs against nine different species of highly pathogenic multidrug resistant bacteria were investigated, also, AuNPs and AgNPs antimicrobial activity were compared to different antibiotics as (Penicillin’s, Aminoglycosides and Cephalosporins) . The results revealed that AuNPs at different concentrations were not efficient against all the nine tested clinical bacterial strains except against Pseudomonas sp. MAM-5, AuNPs were efficient even at lowest concentration (10 ul AuNPs).On the other hand, AgNPs were efficient against all tested strains except Staph.aureus MAM-6 and Staph.epidermidis MAM-5. The biosynthesized AgNPs showed the most effective antimicrobial agent than AuNPs on tested clinical strains and are most effective on Gram-negative bacteria.
Using the standard broth macrodilution method, the MIC, MIC50 and MIC90 were determined, The results of MIC of AuNPs and AgNPs revealed that antimicrobial activity of NPs was strain dependent (i.e. each bacterial strain have its specific sensitivity toward each type of NPs). For example Salmonella sp.(MAM-1), MIC50 was acquired at 100 ul AgNPs while, MIC90 need more concentration (200 ul AgNPs). In case of AuNPs, MIC50 have been acquired at 200 ul AuNPs.
But in case of Salmonella enterica (MAM-2),toreachMIC50, 75 ul of AgNPs and 200 ul of AuNPs were needed.
In case of Pseudomonas spp. (MAM-4 and MAM-5) while, 150 ul of AgNPs could reduced the growth of Pseudomonas MAM-4 by 50% (MIC50), 200 ul of AuNPs was needed to achieve MIC50.The same concentration (150 ul AgNPs) reduced the growth of Pseudomonas MAM-5 by 50% (MIC50) and 200 ul AgNPs resulted in MIC90. This strain of Pseudomonas MAM-5 need 100 ul and 200 ul AuNPs to achieve MIC50 and MIC90 respectively.
The highest concentration (200 ul) of both AgNPs and AuNPs was needed to achieve MIC50 for Staph.aureus MAM-6 and Staph.epidermidis MAM-7 and E.coli MAM-9.
Also, the concentration of 100 ul and 200 ul of AgNPs and AuNPs respectively was needed to reduce the growth of Bacillus subtilis MAM-8by approximately 50 % (MIC50).
While Citrobactersp.MAM-3 was the most sensitive strain against antibiotic discs tested in the present study, it was the worst strain in response to NPs. The highest concentration of AgNPs (200 ul) only reduced the growth by 50% while the same concentration (200 ul) of AuNPs could not achieved even 50 % growth reduction .
On combination of the worst antibiotics Flomox and Pencitard with AgNPs or AuNPs, a synergetic effect have been recorded. Combination of 64ug⁄ml Flomox with 200ul AgNPs or AuNPs reduced the growth of Citrobacter sp. MAM-7 by 85% and 75% respectively. Also AgNPs combined with Pencitard was more efficient than AuNPs combined with Pencitard. Combination of 1024ug⁄ml of Pencitard with 150ul AgNPs reduced Salmonella enterica MAM-2 growth by more than 90% and AuNPs by more than 80%. In case of combination of 1024ug⁄ml of Pencitard with 200ul AgNPs or AuNPs, the growth of Staphylococcus epidermidis MAM-7 was reduced by nearly 90%.
Microorganisms differ greatly in their resistance to ionizing radiation. The resistance of microorganisms is measured by the so called radiation decimal reduction dose (D value). The D 10 value of microorganism is defined either as radiation dose (kGy) necessary to reduce population of that microbe by10 folds (one log cycle) or as the radiation dose required to kill the population. In the present study, using gamma radiation to determine the dose response curves of the two isolates Providenica vermicolaMAM-S20 and Lysinibacillus fusiformis MAM-S17 has been investigated and revealed that thier D10 value after exposure to gamma radiation was 1.029 kGy and 1.126 kGy respectively, which meansthat Providenica vermicola MAM-S20 strain is more sensitive to radiation than Lysinibacillus fusiformis MAM-S17 strain.
Using gamma radiation enhanced the induction of mutants that having different morphological characters anddifferent abilities in production of nanoparticles (AuNPs and AgNPs) compared with that of the parent strain (non-irradiated one). The results revealed that the only mutant that produced AuNPs more than the parent strain was mutant No.2 that exposed to 4.0 kGy producing 1.68 time of that of the parent strain. Also, only mutant No.1 exposed to 3.0 kGy had recorded slight increase (1.08) in AgNPs production than that of parent strain. The other four mutant produced AgNPs less than the parent strain.