الفهرس 
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Abstract
6- Multi drug resistant bacteria have become one of the most important causes of serious opportunistic diseases worldwide. Bacteria are one of the main pathogens of most diseases and epidemics in water, air, or hospital environments. This study aims to isolate and characterize Multi drug resistant bacteria and to synthesize nanoparticles. Our letter includes the cytotoxicity of silver and titanium particles on human cell lines.
1-Bacterial isolation
For this target; fifty isolates were collected and isolated from patient stool laboratory medical samples, these isolates divided into 40 isolates (80 %) were gram Negative and 10 isolates (20%) were gram Positive as primarily microscopic identification for the purified isolates (50). Among all isolates, 25 were with β-hemolysis while other tewenty-five isolates ranging between alpha and gamma.
2-classification of bacteria
Isolates were belonging to five different genera; they belong to E. coli, Staphylococcus aeurus, Klebsiella pneumonia, Acinetobacter beuamani, Pseudomonas aeruginosa.
Genera have different ratios when compared with the total isolates number ninety-eight, these percentages where E. coli (18%), Staphylococcus aeurus (10%), Acinetobacter beumanii (5%), Pseudomonas aeruginosa (8%) and at the last with the final percentage Klebsiella pneumonia (9%).
3- Antibiotic susceptibility
Bet-hemolysis reaction that demonstrated clearly in 25 isolates; among them about six isolates showed multi-resistance against common used fourteen antibiotics from different group according to their mechanism of action on bacterial cell.
Alternative therapeutic strategy against MDR phenomenon was achieved through using nanoparticles specially biosynthesized ones which have lower side effect on the normal cells in comparison with chemically synthesized.
Two metal oxide nanoparticles were tested for their antibacterial activity against the highest ten MDR isolates. AgNPs exhibited antibacterial activity against all ten MDR isolates with MIC 1.25µg/ml. The highest antibacterial activity was recorded for isolate (S024) followed by the two isolates (S014 and S020) with inhibition zone diameters of 15.6, 15.4, and 15.4 mm respectively. At the level of ten isolates; when compared to the combination of Ag with NA and A, AgNPs alone demonstrated greater antibacterial activity against all ten tested bacteria. These two antibiotics were chosen in the combination with AgNPs because they were the most effective against the tested isolates, even though some isolates exhibited resistance to them at levels lower than those of other antibiotics. A combination of AgNPs plus NA had stronger antibacterial activity against the isolates than the combination of Ag plus A, but it was less effective than silver against the 10 isolates.
In the case of titanium of TiO2NPs and its two combinations with NA and ST; Ti alone at MIC 3.21 µg/ml expressed the highest antibacterial activity with seven isolates out of ten. The highest clear zone diameter was for isolate (S020) followed by (S012), (S061), (S018), and (S017) with values of 18, 16, 15, 15, and15mm. A mixture of Ti+ST showed the highest antibacterial activity with one isolate (S07) only with a value (15mm) then it exhibited equal inhibitory activity with titanium alone with two isolates (S024-S03) with14and13mm respectively. The worst results of antibacterial activity appear with a mixture of titanium Ti+NA.
The best option for stopping the development of MDR isolates was two metal oxide NPs alone. In terms of two NPs, TiO2 performed better than Ag NPs with three isolates; these isolates were S-012, S-020, and S-061, with inhibitory zone sizes of 16, 18, and 15 mm, respectively. On the other hand, AgNPs was better with five isolates (S-024, S-027, S-014, S-07, and S-03) with inhibitory diameters of 15.6, 14.9, 15.4, 15.2, and 15mm, respectively
AgNPs have a zeta average of d.nm 152.9; and zeta potential (-20.3mV); while TiO2NPs have a zeta average of d.nm 282.3; with zeta potential (-115mV) which confirmed by TEM.
Three MDR strains were identified through 16S rDNA; their nucleotide sequences were compared against Genebank database through BLASTn which showed that isolate 3, 7 and 17 identified as E. coli, isolate 38 as Acinetobacter baumanii, isolate 41 Pseudomonas. They have accession numbers OP143700, OP143701, OP143702.