In the BALB/c mouse sepsis model, animals are challenged with an intraperitoneal (IP) injection of S. aureus strain with or without 3% mucin. In the mucin model, mice are challenged via injection with the study specific strain in 3% mucin as previously described (Adhikari, et al, 2012; Fattom, et al, 1996) and even low challenge dose (104-5 CFU/ mouse) lead to death. In the non-mucin model, animals receive challenge inoculum without mucin and a higher challenge dose (107-9 CFU/ mouse) is required to achieve LD90.
In both models the animals are monitored for morbidity and mortality twice a day for 14 days post challenge. The mucin model allows for incremental increases in the challenge dose to differentiate dose response at broader ther- apeutic ranges. We have established LD50 values for various strain using this model; typically, lethality occurs within 24-48 hours post infection.