Bacterial strains and culture

The S. Typhimurium strain used in the present study was strain 14028. This bacterium replicates in cockroach gut, persisting for at least a week (Turner et al., 2021). To test the effects of S. Typhimurium type III secretion, strain SPN452, a type III secretion system 1/2 double mutant (invAspiB) derived from strain 14028 was used (Raffatellu et al., 2009). The E. coli strain used in the present study was strain B21, a derivative of E. coli K12 (Ward's Science, Rochester, NY, USA). This bacterium does not replicate in the cockroach gut and quickly declines after it is ingested (Ray et al., 2020). All strains were cultured in liquid LB medium at 37°C.