Abstract: | The larvae of the wax moth,
Galleria
mellonella
, have been used experimentally to host a range of bacterial and fungal pathogens. In this study we evaluated the suitability of
G
. mellonella
as an alternative animal model of
Salmonella
infection. Using a range of inoculum doses we established that the LD50 of
Salmonella
Typhimurium
strain NCTC 12023 was 3.6 × 103 bacteria per larva. Further, a set of isogenic mutant strains depleted of known virulence factors was tested to identify determinants essential for
S
. Typhimurium
pathogenesis. Mutants depleted of one or both of the type III secretion systems encoded by
Salmonella
Pathogenicity Islands 1 and 2 showed no virulence defect. In contrast, we observed reduced pathogenic potential of a phoQ mutant indicating an important role for the PhoPQ two-component signal transduction system. Lipopolysaccharide (LPS) structure was also shown to influence
Salmonella
virulence in
G
. mellonella
. A waaL (rfaL) mutant, which lacks the entire O-antigen (OAg), was virtually avirulent, while a wzz
ST/wzz
fepE double mutant expressing only a very short OAg was highly attenuated for virulence. Furthermore, shortly after infection both LPS mutant strains showed decreased replication when compared to the wild type in a flow cytometry-based competitive index assay. In this study we successfully established a
G
. mellonella
model of
S
. Typhimurium
infection. By identifying PhoQ and LPS OAg length as key determinants of virulence in the wax moth larvae we proved that there is an overlap between this and other animal model systems, thus confirming that the
G
. mellonella
infection model is suitable for assessing aspects of
Salmonella
virulence function. |