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Articles by Hala A. Farrag
Total Records ( 2 ) for Hala A. Farrag
  Hala A. Farrag
  Adhesion of bacteria differing in cell surface hydrophobicity, growth and viability of single isolates of Klebsiella pneumonia, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus epidermidis isolated from catheter associated infections to catheter made of polyurethane, hydrophilic polyurethane, teflon, vialon and siliconised latex was evaluated before and after In vitro exposure to test dose of 25 Gy of gamma radiation. The cell surface hydrophobicity of the tested strains was assessed by hexadecane method. Hydrophobic strains adhered more efficiently to the catheter surface than hydrophilic strains. Low number of the hydrophilic Staphylococcus epidermidis cells can adhere to the polyurethane catheter surface. Irradiation cause a change in the cell surface hydrophobicity of the tested strains. Colonization of polyurethane and hydrophilic polyurethane in phosphate buffered saline (PBS) to non-irradiated and irradiated Klebsiella pneumonia and Escherichia coli was followed by scanning electron microscopy (SEM). Regular sampling of specimens at 1h , 3 h, 8 h, 12h,24 h and 48h. demonstrated colonization and adhesion progression with an increase in the exposure interval of the non irradiated cells to the polyurethane catheter surface followed by cell proliferation, possible break down of catheter components and production of a slimy material covering the bacterial colonies. Adherence and colonization of the irradiated cells showed reduction in cells number along the incubation time with abnormalities in the cells shape and size. While, the adherence of the non-irradiated and irradiated cells to the hydrophilic polyurethane surface showed marked decrease in number of cells with abnormalities in the cells shape and size. Bacterial adherence and colonization of catheters in distilled water were the same as in PBS and slightly delayed in the microcolony formation. Bacterial viability and growth was evaluated in eluates obtained from incubation of segments of each catheter in buffer for 24h. Non of the eluates increase the viability and growth of Staphylococcus epidermidis along the incubation time. However, all of them, significantly increased the growth of non-irradiated (Klebsiella pneumonia, Pseudomonas aeruginosa and Escherichia coli ) with the exception of the eluate from siliconised latex, in which the inoculum count was reduced for E. coli. The initial growth in different catheter eluates was higher for non-irradiated strains than irradiated ones with all biomaterials tested. So, bacterial adherence to catheter may depend in part on the nature of the biomaterial and that substances eluted from the catheters may affect the viability and growth of different microorganisms . The non irradiated strains can grow in catheter eluates and colonies catheter surface better than the irradiated strains. Although, The irradiation change the hydrophobicity of the tested strains as well as reduce the number of cells with abnormalities in shape and size , the irradiated strains also persist on these biomaterials. The implications of these findings may be important in the pathogenesis of foreign body infections and utilization of new biomaterials to prevent bacterial adherence and colonization in immuno-compromised patients.
  Hala A. Farrag
  The usefulness of a test for slime production as a marker for clinically significant infections with Pseudomonas aeruginosa of patients used a medical devices and its implications for therapy were examined before and after in vitro exposure to test dose of 2000 cGys (20 Gy) γ radiation. Some pathogenic strains of Ps. aeruginosa isolated from urine of bladder cancer patients produce a viscid slime when grown on trypticase soy broth (TSB) medium. 80% of clinically implicated strains grew as slimy film coating the glass and polystyrene culture tube walls when propagated in TSB). Slime production was most evident in TSB media containing glucose (0.25% or 1.0% wt./v., casamino acid 3% and yeast extract 1%. There were a strain and media preparation variability of slime production in the presence of other carbohydrates. Two strains were not able to produce slime under any of the tested conditions and the production or non production of slime did not influence growth rate of unirradiated tested strains. The resistance was highest to nalidixic acid followed by colistin lastly tobramycin. Slime-Producing strains were resistant to at least three antibiotics and non- slime producing strains were sensitive to all the tested antibiotics except nalidixic acid and /or colistin and this pattern was changed after irradiation. Slime production, adherent growth, growth characteristics and antimicrobial sensitivity were done to the tested strains before and after in vitro exposure to test dose of 2000cGys γ radiation. The ability of two slime producer strains was changed after irradiation from positive to weak positive or negative. The means difference in antibiotic sensitivity tested before and after radiation were highly statistically significant except in case of ciprofloxacin , colistin, nalidixic acid and ofloxacin. Results suggested that slime mediated adherence may be a critical factor in the pathogenesis of Ps. aeruginosa infections of medical devices. Slime production was usually accompanied by higher incidence of antibiotics resistance because it may act as a mechanical barrier against antibiotics. The change in antimicrobial sensitivity to different antibiotics after irradiation leads to emergence of resistant strains.
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