C57bl 6 male wildtype wt mice

Pathogen-free C57Bl/6 male wildtype (WT) mice were purchased from Charles River Laboratories. S100A9^-/- mice, backcrossed >10 times to a C57BL/6 background, were generated as described [28 (link)], and bred in the animal facility of the host institution. On protein level, intracellular S100A8 is present in S100A9^-/- mice, however due to a lack of S100A9 as a binding partner these mice do not release S100A8/A9 complexes extracellularly and are therefore considered functional knockout (KO) for S100A8/A9 [28 (link),29 (link)]. Age- and sex-matched animals were used in all experiments. For inoculum preparation, S. Typhimurium strain 14028 (ATCC) was grown to mid-logarithmic phase in Lysogeny Broth (LB). Mice were starved for 12 hours followed by oral inoculation with 100 μl (10⁵ or 10⁶ colony forming units (CFU)/100 μl HBSS) bacterial suspension as described [33 (link)–36 (link)]. At 2 and 5 days after infection, mice were anesthetized with Hypnorm (Janssen Pharmaceutical) and midazolam (Roche), blood was drawn into EDTA tubes via cardiac puncture and organs were harvested and homogenized at 4°C. To determine bacterial loads, serial dilutions were plated on horse blood ager (BA) plates and incubated at 37°C for 16 hours.