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Journal of Medical Sciences

Year: 2001 | Volume: 1 | Issue: 4 | Page No.: 244-250
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Authors

Hala A. Farrag

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Research Article

Post Irradiation Effect on Adherent Growth,Slime Formation and Antibiotic Resistance of Pseudomonas aeruginosa Causing Human Infection

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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