Fig. 4: In vivo resistance of LCB against GI tract environment.

a, b Representative IVIS images of mice (a) and their intestinal tracts (b) after oral gavage of uncoated EcN carrying pBBR1MCS2-Tac-eGFP and LCB for 4 h. c Bacterial survival in the stomach at 4 h post-administration. d–f Bacterial presence in the intestine, colon and cecum at (d) 4, (e) 48 and (f) 96 h post-administration, respectively. g Total amount of EcN expressing eGFP retained in the intestinal tract. Each mouse was fed with 1 × 10⁸ CFU of uncoated EcN and LCB by gavage and then sacrificed at 4, 48, and 96 h post-administration. The contents extracted from stomach, intestine, colon and cecum were serially diluted with PBS and then 50 μl of each dilution was spread on solid LB agar plates which were further incubated at 37 °C overnight before counting. h The percentage change of LCB over time. LCB were measured by flow cytometry after incubation in either SGF or SIF at 37 °C for different time points. Error bars represent standard deviation (n = 5). Significance was assessed using Student’s t-test, giving p values, *p < 0.05, **p < 0.01, ***p < 0.005.