Fig. 7

In vivo and in vitro analysis of persistence of E. coli Nissle 1917. Transit of E. coli Nissle was studied by analyzing bacterial persistence in specific organs. L. plantarum was used as control strain. a Schematic representation of the experimental protocol. Female BALB/c mice were treated either orally (5×10¹⁰ CFU/200 µl dose) or intranasally (5×10⁸ CFU/30 µl dose) with either EcN-CBRluc or Lp-CBRluc for 4 consecutive days. In vivo bioluminescent signals were analyzed during and after bacterial application until 8 days. Two hours after application and before in vivo imaging 30 mg/ml of d-luciferin potassium salt substrate was administered intragastrically (200 µl/mouse) in the groups of mice treated orally and 15 µl per nostril in group of mice treated intranasally. Mice were anesthetized and immediately bioluminescence imaging of mice was performed using IVIS. Mouse gut (from stomach to rectum), lungs, and head were immediately excised for ex vivo bioluminescence imaging. EcN* represents EcN-CBRluc. Transit of EcN-CBRluc and Lp-CBRluc on days 4, 5 and 6 after b oral application, c intranasal application. In vivo image contains one representative image of days 4, 5, and 6 containing at least one mouse treated with PBS (middle), EcN-CBRluc (left) and Lp-CBRluc (right). Two mice were sacrificed on each day at 2 h after bacterial application. Mouse gut, lungs, and head were immediately excised for ex vivo bioluminescence imaging. In the similar parallel experiment the persistence of E. coli Nissle and control strain L. plantarum in lungs and gut after oral and intranasal application was analyzed by in vitro colony counts in these organs. Mouse feces and lung samples were collected every day (days 1–11). Two mice were sacrificed at each time point to collect lung samples. Black circles represent EcN-CBRluc counts whereas squares represents Lp-CBRluc counts. Averages of the bacterial CFU counts per 100 mg of feces after d oral application and e intranasal application of bacteria. e Averages of the bacterial CFU counts per 100 mg of lungs after intranasal application of bacteria. Data are representative of two independent experiments (n = 6 mice per group). Error bars show mean ± SEM