003, and 0.060 ± 0.004, respectively; P < 0.01). Again, the ability to form biofilm on polystyrene plates of the twelve strains was not significantly correlated to their ability to form biofilm on IB3-1 cell monolayers (Pearson r, -0.127; P > 0.05). On the other hand, the results of the crystal violet staining showed a statistically significant positive correlation (Pearson r = 0.641; P < 0.05) between adhesiveness and ability to form biofilm GSK872 mw (Figure 5B). Figure 5 Adhesion to and biofilm formation on polystyrene by 12 S. maltophilia isolates from CF patients. A. Adhesion (grey bars)
and biofilm (black bars) levels were Torin 1 supplier assessed by crystal violet colorimetric technique and expressed as optical density read at 492 nm (OD492). OBGTC26 strain adhesiveness was significantly higher than OBGTC49, OBGTC50, and OBGTC52 strains (* P < 0.05; Kruskall-Wallis test followed by Dunn's multiple comparison post-test). Biofilm formed by OBGTC20 strain was significantly higher than that produced by OBGTC9 and OBGTC49 strains (** P < 0.01; Kruskall-Wallis CYC202 clinical trial test followed by Dunn’s multiple comparison post-test). Results are expressed as means + SDs. B. Relationship between adhesion to and biofilm formation levels on polystyrene. A statistically significant positive correlation was found between adhesion and biofilm levels (Pearson r = 0.641; P < 0.05). S. maltophilia internalizes within IB3-1 cells at low levels To ascertain whether our strains
of S. maltophilia are able to enter IB3-1 cells, bacterial internalization was evaluated by a classical antibiotic exclusion assay. Due to high-level of gentamicin resistance, only 5 strains were tested for invasiveness. Gentamicin Microtubule Associated inhibitor was highly effective on inhibiting the growth of the S. maltophilia strains (inhibition of growth ≥ 99.9%, data not shown) and was proved to be not toxic for IB3-1 cells
even when they were exposed up to 1200 μg ml-1, as assessed by the XTT assay (data not shown). The results of the invasion experiments indicated that all strains tested were able to invade IB3-1 cells, albeit at a very low level. Viable intracellular bacteria represented only a minor fraction of the total bacterial input used to infect cell monolayers. Internalization rates (cfus released upon cell lysis, compared to cfus used to infect cell monolayers) were 0.54, 0.01, 4.94, 2.48, 0.03% for OBGTC9, OBGTC10, OBGTC37, OBGTC38, and OBGTC50, respectively. Internalization levels (expressed as number of internalized bacteria) were not significantly related to adhesion levels (expressed as number of adhered bacteria) (Pearson r: 0.044, P > 0.05). Swimming and twitching motilities are not involved in S. maltophilia adhesion to and biofilm formation on IB3-1 cells The motility of our twelve S. maltophilia clinical isolates was assessed by swimming and twitching assays, as described in Materials and Methods. S. maltophilia strains exhibited a very broad range of motility (data not shown). Ten out of 12 (83.