E. coli culture and CFU count.

Mice were given either E. coli^GFP+ (ATCC, 25922GFP) or E. coli^GFP+ expressing full-length Ova via o.p. administration. The Ova plasmid was obtained from AddGene (catalog 25099). Mice were given 5 × 10⁷ GFP E. coli. Mouse weight was monitored daily.

CFU was determined using a plate count protocol. Frozen bacterial stocks were taken from the –80°C freezer, after which a 100 μL tip was passed 3 times through the bacterial stock and then the whole tip was added to a flask with LB Broth (Thermo Fisher Scientific, BP1427-500) and 100 mg/mL of ampicillin (Thermo Fisher Scientific, BP1760-5). The cells were shaken at 37°C and 200 rpm for 19 hours. Dilutions of the bacteria were plated on LB nutrient agar plates and incubated overnight. At the end of the incubation time the plates that had fewer than 30 colonies or more than 300 colonies were discarded due to concerns about accuracy. Plates with colonies between those numbers were counted and the following equation was used to determine CFU/mL: (number of colonies [CFUs])/(dilution × amount plated) = number of bacteria/mL.