Third-generation (G3) female Terc ko/ko mice with a C57Bl/6 background were bred from homozygous parents in the animal facility of the Jena University Hospital. To confirm knockout of Terc, DNA was extracted from the tail of newborn mice using the DNeasy Blood & Tissue Kit (Qiagen, Venlo, Netherlands) according to the manufacturers protocol. The DNA was then used for genotyping via PCR using the following primer sequences: mTR-R: 5′-TTC TGA CCA CCA CCA ACT TCA AT-3′; mTR-WT-F: 5′-CTA AGC CGG CAC TCC TTA CAA G-3′; 5PPgK(-F): 5′-GGG GCT GCT AAA GCG CAT-3′. The results were analyzed with an Agilent 2200 TapeStation system using a Agilent D1000 ScreenTape (both Agilent Technologies, Santa Clara, CA, USA). The WT Terc product had a size of 200 bp while the knockout product had a size of 180 bp. Only mice that showed a single band at 180 bp were used for the further breeding process. The Terc ko/ko mice were used for infection at the age of 8 weeks. Young WT (age 8 weeks) and old WT (age 24 months) C57Bl/6 mice were purchased from Janvier Labs (Le Genest-Saint-Isle, France).
All mice were anesthetized with 2% isoflurane before intranasal infection with S. aureus USA300 (1x10 8 CFU/ml) per mouse. After 24 hours, the mice were weighed and scored as previously described (Hornung et al., 2023) . Infected Terc ko/ko mice were grouped into different degrees of severity based on their clinical score, fatal outcome of the disease (fatal) and the presence of bacteria in organs other than the lung (systemic infection). The mice were sacrificed via injection of an overdose of xylazine/ketamine and bleeding of axillary artery. BAL was collected by instillation and subsequent retrieval of PBS into the lungs. Blood and organs were collected. The organs were stored at -80°C until further usage. Mice cohorts were not blinded to those performing the experiments.