<i>Pa</i> inhibition of <i>Af</i> during biofilm formation.

<p>The data presented show the activity of each live <i>Pa</i> isolate or planktonic- or biofilm-generated <i>Pa</i> culture filtrate on <i>Af</i> during formation of biofilm by <i>Af</i>. Individual isolate results are shown in comparison with their respective <i>Af</i> controls (n = 6 for each). There were five non-CF, five mucoid CF and five non-mucoid CF isolates tested; isolate designations are shown on the x-axis. The bars on the far right of each panel represent the pooled data for each type of isolate (n = 30). Bars represent the mean ± SD of the XTT reduction read at 490 nm. (A) <i>Af</i> conidia were exposed to live <i>Pa</i> cells for 16 h. (B) <i>Af</i> conidia were exposed to <i>Pa</i> planktonic supernatant for 16 h. (C) <i>Af</i> conidia were exposed to <i>Pa</i> biofilm supernatant for 16 h. The resulting readings were determined. “XTT metabolic activity” refers to the spectrophotometric absorbance of the formazan reduction product of XTT at 490 nm. Assays were performed in blocks with two runs of triplicates done on different days, for each <i>Pa-Af</i> combination. Panel (A) All individual <i>Pa</i> isolates, noted on the x-axis, were significantly inhibitory compared to controls (<i>P</i><0.001). The four bars on the right side show the pooled data. CF mucoid and CF non-mucoid cells were more inhibitory than non-CF <i>Pa</i> cells (<i>P</i><0.001, both comparisons), with CF non-mucoid cells more inhibitory than CF mucoid cells (<i>P</i><0.001). Panel (B) Planktonic culture filtrate from all individual <i>Pa</i> isolates, were significantly inhibitory compared to controls (<i>P</i><0.001). Pooled data analysis showed both CF mucoid or CF non-mucoid isolate culture filtrate was more inhibitory than that from non-CF isolates (<i>P</i><0.001, both comparisons) and non-mucoid was more inhibitory than mucoid (<i>P</i> < 0.001). Panel (C) Culture filtrates from all <i>Pa</i> isolates grown as biofilm were significantly inhibitory (<i>P</i><0.001). Pooled data showed culture filtrate from CF non-mucoid isolates under biofilm conditions was more inhibitory than that from CF mucoid or non-CF isolates under the same conditions (<i>P</i><0.001, both comparisons), and that non-mucoid CF filtrates were more inhibitory than mucoid isolate filtrates (<i>P</i> < 0.001).