## 2 Results
### Anti-Biofilm Activity vs. Cyctic Fibrosis Isolates  
To assess the biofilm-forming ability of the different clinical isolates, dilutions (1/100) of overnight cultures were incubated in 96-well polypropylene plates using BM2 glucose medium, as previously described [22]. No apparent correlation was observed between the different bacterial morphologies and the formation of biofilm biomass of _P. aeruginosa_ isolates (Table 2). Three _P. aeruginosa_ strains with classical morphology C2773, 3195, and 1172, and mucoid strain 2639 exhibited increased biofilm formation when compared to reference strains PA01 and PA14 (Table 2). In contrast, strains _B. cenocepacia_ CEP0055 and _B. ambigaria_ CEP0996 produced about a third of the biofilm compared to the previously-studied strain _B. cenocepacia_ 4813 (Table 2). Overall, five of the eight tested _Burkholderia_ strains showed relatively weak biofilm formation on the surface of the microtiter wells (Table 2).  
\begin{table}
\begin{tabular}{l l l} \hline
**Strains** & **Biofilm** & **Inhibition by** \\
**(Colonial Morphology or Genomovar)** & **Formation \({}^{\text{a}}\)** & **10 \(\mu\)g/mL 1018** \\ \hline _P. aeruginosa_ PA01 & \(0.79\pm 0.22\) & 51\% \\ _P. aeruginosa_ PA14 & \(0.82\pm 0.21\) & 49\% \\ _P. aeruginosa_ 3195 (Classic) & \(0.99\pm 0.16\) & 37\% \\ _P. aeruginosa_ C2773 (Classic) & \(0.89\pm 0.17\) & 60\% \\ _P. aeruginosa_ 1172 (Classic) & \(0.92\pm 0.27\) & 37\% \\ _P. aeruginosa_ 7632 (Classic) & \(0.59\pm 0.12\) & 19\% \\ _P. aeruginosa_ 3330 (Classic) & \(0.84\pm 0.20\) & 33\% \\ _P. aeruginosa_ 4020 (Classic) & \(0.62\pm 0.16\) & 53\% \\ _P. aeruginosa_ C4276 (Classic) & \(0.62\pm 0.28\) & 53\% \\ _P. aeruginosa_ 2631 (Classic) & \(0.74\pm 0.27\) & 44\% \\ _P. aeruginosa_ C4278 (Mucoid) & \(0.73\pm 0.20\) & 58\% \\ _P. aeruginosa_ 4608 (Mucoid) & \(0.62\pm 0.09\) & 67\% \\ _P. aeruginosa_ 2639 (Mucoid) & \(0.93\pm 0.20\) & 44\% \\ _P. aeruginosa_ 7633 (Entire) & \(0.72\pm 0.16\) & 49\% \\ _P. aeruginosa_ 2955 (Dwarf) & \(0.64\pm 0.19\) & 41\% \\ _B. multivorans_ D2661 (Genomovar II) & \(0.75\pm 0.07\) & 75\% \\ _B. cenocepacia_ 4813 (IIIa) & \(0.94\pm 0.18\) & 52\% \\ \hline \end{tabular}
\end{table}
Table 2: Activity of peptide 1018 against biofilms formed by _P. aeruginosa_ (PA) and _Burkholderia_ (B) clinical isolates from cystic fibrosis (CF) patients. Usually three, but at least two independent experiments and eighteen replicates were performed per condition. The differentiating colony morphology or genomovar is given in brackets in the first column. Strains PAO1 and PA14 are reference strains that have been fully sequenced.  
These strains were then challenged with sub-inhibitory levels of anti-biofilm peptide 1018. At 10 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, the peptide was able to reduce PA01 and PA14 biofilm formation by \(\sim\)50% (\(p<0.05\); Table 2). Similarly, biofilms formed by different \(P\). _aeruginosa_ clinical isolates were also susceptible to the peptide (Table 2). Biofilms formed by classic morphology strains C2773, C4276, and 4020, and mucoid strains C4278 and 4608 were inhibited by at least 50% by the peptide (Table 2). On the other hand, biofilms produced by with classic strains 3195, 7632, 3330, 1172, and 2631, mucoid strain 2639, and dwarf (_i.e._, small-colony variant) strain 2955 were somewhat less susceptible to the peptide (Table 2). Biofilm biomass was also significantly reduced by 52%-75%, upon peptide challenge in _Burkholderia_ strains belonging to different genomovars, and this appeared to be independent of the relative ability of each strain to form biofilms (Table 2), as well as the resistance of planktonic cells to treatment with peptide 1018 (Table 1).