Depletion of butyrate-producing Clostridia from the gut microbiota drives an aerobic luminal expansion of Salmonella

Rivera-Chávez F, Zhang LF, Faber F, Lopez CA, Byndloss MX, Olsan EE, Xu G, Velazquez EM, Lebrilla CB, Winter SE, Bäumler AJ.

Cell Host Microbe. (2016) Apr 13;19(4):443-54

Speaker: Shih-Hsuan Lin (林詩璇)                              Time: 14:00~15:00, May. 17, 2017

Commentator: Dr. I-Hsiu Huang (黃一修老師)           Place: Room 601

Abstract:

Salmonella enterica serovars Typhimurium (S. Typhimurium) are gram-negative, facultative anaerobic rod-shaped bacteria. Antibiotic usage is a risk factor for developing Salmonella-induced gastroenteritis, increasing susceptibility to enteric pathogens, and depleting butyrate-producing Clostridia ⁽¹⁾.The aerobic respiration and nitrate respiration in S. Typhimurium provide a growth advantage during the course of colitis caused by this pathogen. In addition, S. Typhimurium survive in tissue by using type III secretion system-1 (T3SS-1) and T3SS-2-mediated epithelial invasion and trigger acute intestinal inflammation ⁽²⁾. However, the mechanisms contributing to the post-antibiotic expansion of S. Typhimurium remain to be elucidated. To identify whether aerobic respiration and nitrate respiration contribute to the bacterial expansion, the cytochrome bd-II oxidase-deficient mutant strain (cyxA mutant) and nitrate reductases-deficient mutant strain(narG napA narZ mutant) were utilized for the experiments. To investigate whether the bacterial virulence factors were required to support luminal growth by aerobic respiration, T3SS-1 and T3SS-2-deficient mutant strain (invA spiB mutant) were used. The results showed that streptomycin treatment depleted butyrate-producing Clostridia from the mouse intestinal lumen, leading to decreased butyrate levels and increased epithelial oxygenation, and the expansion of S. Typhimurium. Clostridiadepletion and S. Typhimurium expansion were also observed in the absence of antibiotic treatment in genetically resistant mice and it required the Salmonella type III secretion systems. These findings indicated that S. Typhimurium virulence factors and antibiotic treatment promote pathogen expansion by depletion of butyrate-producing Clostridia to elevate epithelial oxygenation.

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