Tryptone soy

Escherichia coli strain STCC 4201, provided by the Spanish Type Culture Collection (STCC), was used. The bacterial culture was frozen at -80°C in cryovials. Stationary-phase cultures were prepared by inoculating 5 mL of tryptone soy broth (Oxoid, Hampshire, UK) supplemented with 0.6% (w/v) yeast extract (Oxoid; TSBYE) with a colony grown on tryptone soy agar (Oxoid) supplemented with 0.6% (w/v) yeast extract (TSAYE). The precultures were incubated at 35°C for 6 h in a shaking incubator. Fifty microliters of the precultures were inoculated into 50 mL of fresh TSBYE and incubated for 24 h under the same conditions, which resulted in stationary-phase cultures containing approximately 2 × 10⁹ CFU/mL.

Antibacterial activity was determined according to Tang et al. (20 (link)). dTHP-1 cells were seeded in 6 well plates and primed with DCATH-2 or medium as described. Log-phase culture of Salmonella enterica subsp. enterica serovar enteritidis 706 (Se706) was added to each well at a MOI of 1. After 2 h incubation at 37°C, cells were washed twice with warm Dulbecco’s Phosphate buffered saline (DPBS; Life technologies) and further incubated for 1 h at 37°C with IMDM/FBS medium containing 300 µg/ml colistin (MP biochemicals, Santa Ana, CA, USA). After incubation, cells were washed 3 times in DPBS and the lysed with 1% triton X-100. Well contents were serially diluted in tryptone soy broth (Oxoid, Basingstoke, UK), plated on tryptone soy agar and counted after 24 h at 37°C.