Functional and Genomic Variation between Human-Derived Isolates of Lachnospiraceae Reveals Inter- and Intra-Species Diversity.

Bacteria belonging to the Lachnospiraceae family are abundant, obligate anaerobic members of the microbiota in healthy humans. Lachnospiraceae impact their hosts by producing short-chain fatty acids, converting primary to secondary bile acids, and facilitating colonization resistance against intestinal pathogens. To increase our understanding of genomic and functional diversity between members of this family, we cultured 273 Lachnospiraceae isolates representing 11 genera and 27 species from human donors and performed whole-genome sequencing assembly and annotation. This analysis revealed substantial inter- and intra-species diversity in pathways that likely influence an isolate's ability to impact host health. These differences are likely to impact colonization resistance through lantibiotic expression or intestinal acidification, influence host mucosal immune cells and enterocytes via butyrate production, or contribute to synergism within a consortium by heterogenous polysaccharide metabolism. Identification of these specific functions could facilitate development of probiotic bacterial consortia that drive and/or restore in vivo microbiome functions.

Microbiota-derived lantibiotic restores resistance against vancomycin-resistant Enterococcus.

Intestinal commensal bacteria can inhibit dense colonization of the gut by vancomycin-resistant Enterococcus faecium (VRE), a leading cause of hospital-acquired infections1,2. A four-strained consortium of commensal bacteria that contains Blautia producta BPSCSK can reverse antibiotic-induced susceptibility to VRE infection3. Here we show that BPSCSK reduces growth of VRE by secreting a lantibiotic that is similar to the nisin-A produced by Lactococcus lactis. Although the growth of VRE is inhibited by BPSCSK and L. lactis in vitro, only BPSCSK colonizes the colon and reduces VRE density in vivo. In comparison to nisin-A, the BPSCSK lantibiotic has reduced activity against intestinal commensal bacteria. In patients at high risk of VRE infection, high abundance of the lantibiotic gene is associated with reduced density of E. faecium. In germ-free mice transplanted with patient-derived faeces, resistance to VRE colonization correlates with abundance of the lantibiotic gene. Lantibiotic-producing commensal strains of the gastrointestinal tract reduce colonization by VRE and represent potential probiotic agents to re-establish resistance to VRE.

Sociodemographic variation in the oral microbiome.

PURPOSE: Variations in the oral microbiome are potentially implicated in social inequalities in oral disease, cancers, and metabolic disease. We describe sociodemographic variation of oral microbiomes in a diverse sample. METHODS: We performed 16S rRNA sequencing on mouthwash specimens in a subsample (n = 282) of the 2013-2014 population-based New York City Health and Nutrition Examination Study. We examined differential abundance of 216 operational taxonomic units, and alpha and beta diversity by age, sex, income, education, nativity, and race/ethnicity. For comparison, we examined differential abundance by diet, smoking status, and oral health behaviors. RESULTS: Sixty-nine operational taxonomic units were differentially abundant by any sociodemographic variable (false discovery rate < 0.01), including 27 by race/ethnicity, 21 by family income, 19 by education, 3 by sex. We found 49 differentially abundant by smoking status, 23 by diet, 12 by oral health behaviors. Genera differing for multiple sociodemographic characteristics included Lactobacillus, Prevotella, Porphyromonas, Fusobacterium. CONCLUSIONS: We identified oral microbiome variation consistent with health inequalities, more taxa differing by race/ethnicity than diet, and more by SES variables than oral health behaviors. Investigation is warranted into possible mediating effects of the oral microbiome in social disparities in oral and metabolic diseases and cancers.

Tobacco exposure associated with oral microbiota oxygen utilization in the New York City Health and Nutrition Examination Study.

PURPOSE: The effect of tobacco exposure on the oral microbiome has not been established. METHODS: We performed amplicon sequencing of the 16S ribosomal RNA gene V4 variable region to estimate bacterial community characteristics in 259 oral rinse samples, selected based on self-reported smoking and serum cotinine levels, from the 2013-2014 New York City Health and Nutrition Examination Study. We identified differentially abundant operational taxonomic units (OTUs) by primary and secondhand tobacco exposure, and used "microbe set enrichment analysis" to assess shifts in microbial oxygen utilization. RESULTS: Cigarette smoking was associated with depletion of aerobic OTUs (Enrichment Score test statistic ES = -0.75, P = .002) with a minority (29%) of aerobic OTUs enriched in current smokers compared with never smokers. Consistent shifts in the microbiota were observed for current cigarette smokers as for nonsmokers with secondhand exposure as measured by serum cotinine levels. Differential abundance findings were similar in crude and adjusted analyses. CONCLUSIONS: Results support a plausible link between tobacco exposure and shifts in the oral microbiome at the population level through three lines of evidence: (1) a shift in microbiota oxygen utilization associated with primary tobacco smoke exposure; (2) consistency of abundance fold changes associated with current smoking and shifts along the gradient of secondhand smoke exposure among nonsmokers; and (3) consistency after adjusting for a priori hypothesized confounders.

Inhibiting antibiotic-resistant Enterobacteriaceae by microbiota-mediated intracellular acidification.

Klebsiella pneumoniae, Escherichia coli, and other members of the Enterobacteriaceae family are common human pathogens that have acquired broad antibiotic resistance, rendering infection by some strains virtually untreatable. Enterobacteriaceae are intestinal residents, but generally represent <1% of the adult colonic microbiota. Antibiotic-mediated destruction of the microbiota enables Enterobacteriaceae to expand to high densities in the colon, markedly increasing the risk of bloodstream invasion, sepsis, and death. Here, we demonstrate that an antibiotic-naive microbiota suppresses growth of antibiotic-resistant clinical isolates of Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis by acidifying the proximal colon and triggering short chain fatty acid (SCFA)-mediated intracellular acidification. High concentrations of SCFAs and the acidic environment counter the competitive edge that O2 and NO3 respiration confer upon Enterobacteriaceae during expansion. Reestablishment of a microbiota that produces SCFAs enhances clearance of Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis from the intestinal lumen and represents a potential therapeutic approach to enhance clearance of antibiotic-resistant pathogens.