Fig. 4

Antibiotic treatment decreased ROS production in the intestinal mucosa, peroxynitrite production of AMs and increased PA pneumonia-induced neutrophil infiltration in the lung. FOS or dead L. salivarius feeding reversed effects of antibiotic treatment. a Intramuscular combined antibiotic was given to mice for 6 days and ROS production in the intestinal mucosa was examined with the production of DCFDA. The levels of ROS in the intestinal mucosa were analyzed by DCFDA fluorescent dye, which was added into the suspension of intestinal mucosa for the cultivation. DCFDA is oxidized by ROS into 2ʹ7ʹ-dichlorofluorescein (DCF). DCF is detected by fluorescence spectroscopy with excitation and emission spectra of 495 and 529 nm, respectively. Data are presented as mean ± SEM. b Intramuscular combined antibiotic was given to mice for 6 days and AMs were purified from BALF for peroxynitrite production assay. The collected AMs were cultured with phenol red containing 25 μM of 1,2,3-dihydrorhodamine. The cells were stimulated with E. coli LPS. Peroxynitrite was measured every 15 min for 75 min using excitation and emission wavelengths of 485 and 530 nm, respectively. Data are presented as mean ± SEM. c Intramuscular combined antibiotic with or without FOS or dead L. salivarius feeding was given to mice for 6 days. The trachea of mice was surgically exposed and 50 µl (1.0 × 10⁷ CFU P. aeruginosa) were instilled via an angiocatheter through the trachea to induce P. aeruginosa pneumonia and neutrophil infiltration in the lungs was examined. Data are presented as mean ± SEM; PA, P. aeruginosa; DCF, 2ʹ7ʹ-dichlorofluorescein; FOS, fructo-oligosaccharides; MPO, myeloperoxidase; dLac, dead L. salivarius. *P < 0.05, **P < 0.01, ***P < 0.001