The human intestine, colonized by a dense community of resident microbes, is a frequent target of bacterial pathogens. Undisturbed, this intestinal microbiota provides protection from bacterial infections. Conversely, disruption of the microbiota with oral antibiotics often precedes the emergence of several enteric pathogens1,2,3,4. How pathogens capitalize upon the failure of microbiota-afforded protection is largely unknown. Here we show that two antibiotic-associated pathogens, Salmonella enterica serovar Typhimurium (S. typhimurium) and Clostridium difficile, use a common strategy of catabolizing microbiota-liberated mucosal carbohydrates during their expansion within the gut. S. typhimurium accesses fucose and sialic acid within the lumen of the gut in a microbiota-dependent manner, and genetic ablation of the respective catabolic pathways reduces its competitiveness in vivo. Similarly, C. difficile expansion is aided by microbiota-induced elevation of sialic acid levels in vivo. Colonization of gnotobiotic mice with a sialidase-deficient mutant of Bacteroides thetaiotaomicron, a model gut symbiont, reduces free sialic acid levels resulting in C. difficile downregulating its sialic acid catabolic pathway and exhibiting impaired expansion. These effects are reversed by exogenous dietary administration of free sialic acid. Furthermore, antibiotic treatment of conventional mice induces a spike in free sialic acid and mutants of both Salmonella and C. difficile that are unable to catabolize sialic acid exhibit impaired expansion. These data show that antibiotic-induced disruption of the resident microbiota and subsequent alteration in mucosal carbohydrate availability are exploited by these two distantly related enteric pathogens in a similar manner. This insight suggests new therapeutic approaches for preventing diseases caused by antibiotic-associated pathogens.
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European Nucleotide Archive
Gene Expression Omnibus
Microbiota enumeration (16S rRNA) datasets have been deposited in the EMBL European Nucleotide Archive (ENA) under accession number ERP003629 and can also be found in the QIIME Database under the study ID 1958 (http://www.microbio.me/qiime/). Gene Chip datasets are available in the GEO database under accession number GSE49076.
We thank E. Sonnenburg for comments on the manuscript; M. St. Onge for technical assistance; and A. Shen, N. Minton and R. Knight for valuable help and reagents. This research was supported by R01-DK085025 (to J.L.S.), NSF graduate fellowships (to K.M.N. and J.A.F) and a Stanford Graduate Fellowship (to K.M.N.). J.L.S. holds an Investigators in the Pathogenesis of Infectious Disease Award from the Burroughs Wellcome Fund.
This file contains Supplementary Figures 1-11 and Supplementary Tables 1-3.
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Epithelial-microbial diplomacy: escalating border tensions drive inflammation in inflammatory bowel disease
Intestinal Research (2019)