Microbiology & Immunology Publications

Predictors of urinary tract infection after menopause: A prospective study [6] (multiple letters)

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The physico-chemical cell-surface properties of Pseudomonas aeruginosa AK1 and its adhesion to silicone rubber under flow were compared for cells suspended in phosphate-buffered saline (PBS) or PBS supplemented with 2% nutrient broth. Addition of 2% nutrient broth to cells suspended in PBS yielded minimal growth and did not significantly change the mean zeta potential of the organisms, which was around -13 mV. However, a comparatively larger proportion of the organisms had more negative zeta potentials in the presence of nutrient broth. This change was concurrent with a slight decrease in cell-surface hydrophobicity, as measured by water contact angles, from 119°to around 112°. The initial deposition rate of P. aeruginosa AK1 to silicone rubber, as studied in a parallel plate flow chamber, increased from 344 cm s in the absence of nutrient broth to 505 cm s in its presence. No stationary level of adhesion was observed in the presence of nutrient broth, instead the number of adhering cells increased steadily at a rate of approximately 85 cm s . Fluorescent staining of adhering cells demonstrated that for adhesion from buffer only 2% of the adhering cells were metabolically active, whereas in case of deposition from PBS supplemented with nutrient broth, 67% of the adhering cells were metabolically active. It is concluded that the deposition rates measured in the parallel plate flow chamber with 2% nutrient broth added to the PBS suspension represent an interplay of adhesion and surface-associated growth. -2 -1 -2 -1 -2 -1

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