Adherent biofilms were stained with crystal violet, followed by ethanol solubilization of the crystal violet and quantification (A 595nm) of stained wells. The box plots (median, thick line in the box) represent the mean of 3 independent biological repeats, each assayed in quintuplicate (n = 15). *** indicates a statistically significant difference (p < 0.001), between the typA mutant and PA14 WT as determined by Whitney Mann test. However, the investigation GDC 0032 of flagellum-mediated swimming and swarming motility as well as the type IV pilus-mediated twitching motility, which are all involved in attachment and subsequent

biofilm development, revealed no differences between mutant and wild type Pevonedistat chemical structure strain (data not shown) ruling out defects in the biosynthesis and function of these cellular appendages in the typA mutant. Smad cancer Antibiotic susceptibility testing Since recent studies have demonstrated a role for TypA in multidrug resistance in E. coli[28], we studied the impact of the typA gene in antibiotic resistance of P. aeruginosa against a variety of different antimicrobial compounds. As shown in Table 1, the typA mutant exhibited a consistent 2-fold increase in susceptibility to the cationic peptides polymyxin B and colistin, the ß-lactam antibiotics ceftazidime and meropenem, as well as tetracycline in comparison to the parent

strain. This altered susceptibility could be complemented by introducing wild type copies of typA into the mutant strain. see more No change in susceptibility was observed regarding the fluoroquinolone ciprofloxacin, the aminoglycoside tobramycin, and the cationic host defence peptide LL-37 (Table 1). Table 1 MICs of different antibiotics towards P. aeruginosa PA14 WT, PA14 typA mutant and complemented

mutant PA14 typA ::p typA +a   MIC (μg/ml) Antibiotic PA14 WT PA14typA PA14typA::ptypA + Ciprofloxacin 0.03 0.03 0.03 Meropenem 2 1 2 Ceftazidime 4 2 4 Tetracycline 8 4 8 Tobramycin 0.25 0.25 0.25 Polymyxin B 0.5 0.25 0.5 Colistin 0.25 0.125 0.25 LL-37 16 16 16 aMICs were determined by serial 2-fold dilutions in MH-medium. The MIC represents the concentration at which no growth was visually observed after 24 h of incubation at 37°C. The values shown are the modes of 4 to 6 independent experiments. Reduced virulence of PA14 typA due to down-regulation of the Type III secretion system Previous studies have shown, that uptake by and killing of eukaryotic host cells is highly dependent on the Type III secretion system in P. aeruginosa[5, 29, 30]. To analyze the potential molecular basis for reduced virulence of the typA mutant observed in our experiments, we investigated gene expression of known virulence-associated genes in P. aeruginosa using qRT-PCR on bacterial RNA of wild type and typA mutant strain isolated during host-pathogen interaction with D. discoideum.