Phage therapy is an old method of combating bacterial pathogens that has recently been taken into consideration due to the alarming spread of antibiotic resistance. Escherichia coli O157:H7 is a foodborne pathogen that causes hemorrhagic colitis and life-threatening Hemolytic Uremic Syndrome (HUS). There are several studies on isolation of specific phages against E. coli O157:H7 and more than 60 specific phages have been published so far. Although in vitro experiments have been successful in elimination or reduction of E. coli O157:H7numbers, in vivo experiments have not been as promising. This may be due to escape of bacteria to locations where phages have difficulties to enter or due to the adverse conditions in the gastrointestinal tract that affect phage viability and proliferation. To get around the latter obstacle, an alternative phage delivery method such as polymer microencapsulation should be tried. While the present time results are not very encouraging the work should be continued as more efficient phage treatment regimens might be found in future.

The present study was designed to isolate bacterial strain capable of tellurium nanorods' (Te NRs) production followed by purification and evaluation of the cytotoxic effect of Te NRs. Among 25 environmental samples collected for screening of Te NR-producer bacterial strains one bacterial colony (isolated from hot spring and identified as Pseudomonas pseudoalcaligenes strain Te) was selected and applied for biosynthesis of Te NRs. Thereafter, an organic-aqueous partitioning system was applied for the purification of the biogenic Te NRs and the purified Te NRs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction spectroscopy (XRD), UV-visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR) techniques. The cytotoxic effect of biologically synthesized Te NRs and potassium tellurite on four cell lines of MCF-7, HT1080, HepG2 and A549 was then determined using the MTT assay method. The obtained results revealed lower toxicity for the rod-shaped biogenic tellurium nanostructures (~22nm diameter by 185nm length) compared to K2TeO3.

Background: Recent theranostic (therapeutic or diagnostic) applications of tellurium nanoparticles have attracted a great interest for development of diff erent methods for synthesis of this valuable nanostructure, especially via biological resources. Objectives: In the present study, the antimicrobial and antioxidant eff ects of the tellurium nanorods (Te NRs) biosynthesized by a bacterial strain Pseudomonas pseudoalcaligenes strain Te were evaluated. Materials and Methods:The antimicrobial eff ect of Te NRs and potassium tellurite against diff erent bacterial and fungal pathogens was assessed by microdilution method. Furthermore, the disk diff usion method was used to evaluate the antibacterial eff ect of the biogenic Te NRs and potassium tellurite against methicillin-resistant Staphylococcus aureus, alone or in combination with various antibiotics. Also, the biogenic Te NRs were investigated for antioxidant activity using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and reducing power assay. Results: Transmission electron micrograph (TEM) of the purifi ed Te NRs showed individual and rod-shaped nanostructure (~22 nm diameter by 185 nm in length). Based on the data obtained from both microdilution and disk diff usion method the K 2 TeO 3 exhibited a higher antibacterial and antifungal activity compared to the Te NRs. The measured IC 50 for the biogenic Te NRs (i.e. DPPH radical scavenging activity) was found to be 24.9 μg.mL -1 , while, K 2 TeO 3 has represented only 17.6 ± 0.8 % DPPH radical scavenging eff ect at the concentration of 160 μg.mL -1 . The reducing power assay revealed a higher electron-donating activity for Te NRs compared to K 2 TeO 3 . Conclusions: Based on the data obtained from both microdilution and disk diff usion method the K 2 TeO 3 exhibited a higher antimicrobial and antifungal activity than Te NRs. Te NRs didn't show the antibacterial eff ect against the tested bacterial strain: MRSA and showed an inhibitory eff ect and antibacterial activity of the eff ective antibiotics. However, more studies should be performed to explore the action mechanism of the produced biogenic Te NRs.

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