Galleria mellonella Infection Model

Larvae of the greater wax moth Galleria mellonella were obtained from Reptilienkosmos (Niederkrüchten, Germany). Infection experiments were carried out as described elsewhere [24 (link)]. In short, S. pyogenes strains were grown overnight in THY, washed twice in a 0.9% NaCl solution and suspended in 0.9% NaCl to a final concentration of 1.5-2x10⁸ CFU/ml. Larvae with a weight of 150–200 mg were inoculated with 10 μl of this bacterial suspension, resulting in an infection dose of 1.5–2 x 10⁶ CFU/larva. Bacteria were injected into the hemocoel of the larvae between the last pair of legs using a microapplicator (World Precisions Instruments, Sarasota, USA) and a fine dosage syringe (Omnican-F, 0.01 ml–1 ml, 0.30x12 mm, B. Braun AG, Melsungen, Germany). As a control, larvae were mock inoculated with 10 μl of a 0.9% NaCl solution. Survival of the larvae was observed for seven days. Larvae were regarded dead when they did not move upon repeated physical stimulation with tweezers.