Beyond Fecal Microbiota Transplantation: Developing Drugs from the Microbiome.

The transfer of live gut microbes may transform patient care across a range of autoimmune, metabolic, hepatic, and infectious diseases. One early approach, fecal microbiota transplantation, has shown promise in Clostridiodes difficile infection and the potential for improving clinical and public health outcomes for other antibiotic-resistant bacteria. These clinical successes have motivated the development of microbiome drugs, which will need to address challenges in safety, uniformity, and delivery while seeking to preserve the benefits of using whole microbiome communities as novel therapeutics and an innovative platform for drug discovery.

Microbiome predictors of dysbiosis and VRE decolonization in patients with recurrent C. difficile infections in a multi-center retrospective study.

The gastrointestinal microbiome is intrinsically linked to the spread of antibiotic resistance. Antibiotic treatment puts patients at risk for colonization by opportunistic pathogens like vancomycin resistant Enterococcus and Clostridioides difficile by destroying the colonization resistance provided by the commensal microbiota. Once colonized, the host is at a much higher risk for infection by that pathogen. Furthermore, we know that microbiome community differences are associated with disease states, but we do not have a good understanding of how we can use these changes to classify different patient populations. To that end, we have performed a multicenter retrospective analysis on patients who received fecal microbiota transplants to treat recurrent Clostridioides difficile infection. We performed 16S rRNA gene sequencing on fecal samples collected as part of this study and used these data to develop a microbiome disruption index. Our microbiome disruption index is a simple index that is predictive across cohorts, indications, and batch effects. We are able to classify pre-fecal transplant vs post-fecal transplant samples in patients with recurrent C. difficile infection, and we are able to predict, using previously-published data from a cohort of patients receiving hematopoietic stem cell transplants, which patients would go on to develop bloodstream infections. Finally, we also identified patients in this cohort that were initially colonized with vancomycin resistant Enterococcus and that 92% (11/12) were decolonized after the transplant, but the microbiome disruption index was unable to predict such decolonization. We, however, were able to compare the relative abundance of different taxa between the two groups, and we found that increased abundance of Enterobacteriaceae predicts whether patients were colonized with vancomycin resistant Enterococcus. This work is an early step towards a better understanding of how microbiome predictors can be used to help improve patient care and patient outcomes.

Fecal Microbiota Transplantation in Patients With Primary Sclerosing Cholangitis: A Pilot Clinical Trial.

BACKGROUND: Primary sclerosing cholangitis (PSC) is a cholestatic liver disease with no effective medical therapies. A perturbation of the gut microbiota has been described in association with PSC, and fecal microbiota transplantation (FMT) has been reported to restore the microbiome in other disease states. Accordingly, we aimed at evaluating the safety, change in liver enzymes, microbiota, and metabolomic profiles in patients with PSC after FMT. METHODS: An open-label pilot study of patients with PSC with concurrent inflammatory bowel disease and alkaline phosphatase (ALP) > 1.5× the upper limit of normal was conducted. The patients underwent a single FMT by colonoscopy. Liver enzyme profiles and stool microbiome and metabolomic analysis were conducted at baseline and weeks 1, 4, 8, 12, and 24 post-FMT. The primary outcome was safety, and the secondary outcome was a decrease in ALP levels ≥50% from baseline by week 24 post-FMT; stool microbiota (by 16S rRNA gene profiling) and metabonomic dynamics were assessed. RESULTS: Ten patients underwent FMT. Nine patients had ulcerative colitis, and 1 had Crohn's colitis. The mean baseline ALP level was 489 U/L. There were no related adverse events. Overall, 30% (3/10) experienced a ≥50% decrease in ALP levels. The diversity increased in all patients post-FMT, as early as week 1 (P < 0.01). Importantly, abundance of engrafter operational taxonomic units in patients post-FMT correlated with decreased ALP levels (P = 0.02). DISCUSSION: To our knowledge, this is the first study to demonstrate that FMT in PSC is safe. In addition, increases in bacterial diversity and engraftment may correlate with an improvement in ALP among patients with PSC.

Correction to: Fecal Microbiota Transplantation Capsules with Targeted Colonic Versus Gastric Delivery in Recurrent Clostridium difficile Infection: A Comparative Cohort Analysis of High and Low Dose.

The original version of the article unfortunately contained an error in article title. The corrected title is 'Fecal Microbiota Transplantation Capsules with Targeted Colonic Versus Gastric Delivery in Recurrent Clostridium difficile Infection: A Comparative Cohort Analysis of High and Low Dose'.

Fecal Microbiota Transplantation Capsules with Targeted Colonic Versus Gastric Delivery in Recurrent Clostridium difficile Infection: A Comparative Cohort Analysis of High and Lose Dose.

BACKGROUND: Fecal microbiota transplantation (FMT) is an effective therapy for recurrent Clostridium. difficile infection (rCDI). FMT capsules have emerged, and it is unknown if delivery location and dose impact efficacy. METHODS: We compared two cohorts of patients receiving two capsule formulations: gastric release (FMTgr) and targeted colonic release (FMTcr) at two different sites. Cohort A received FMTgr at (1) high dose: 60 capsules and low dose: 30 capsules. Patients in Cohort B received FMTcr at (1) high dose: 30 capsules (2) low dose: 10 capsules. Clinical cure rates and adverse events were monitored through week 8. Paired t-tests were used to compare diversity pre- and post-FMT. RESULTS: 51 rCDI patients were enrolled. Cohort A contained n = 20 and Cohort B contained n = 31. Overall cure at week 8 for FMTgr was 75% (15/20) compared to 80.6% for FMTcr, (25/31), p = 0.63. Both formulations were safe with no serious adverse events. FMTcr was superior at increasing gut microbial diversity. DISCUSSION: To our knowledge, this is the first study to compare targeted delivery of FMT capsules. While both capsules were safe and efficacious, microbial engraftment patterns were superior in FMTcr.

Exploration of immunoglobulin transcriptomes from mice immunized with three-finger toxins and phospholipases A2 from the Central American coral snake, Micrurus nigrocinctus.

Snakebite envenomings represent a neglected public health issue in many parts of the rural tropical world. Animal-derived antivenoms have existed for more than a hundred years and are effective in neutralizing snake venom toxins when timely administered. However, the low immunogenicity of many small but potent snake venom toxins represents a challenge for obtaining a balanced immune response against the medically relevant components of the venom. Here, we employ high-throughput sequencing of the immunoglobulin (Ig) transcriptome of mice immunized with a three-finger toxin and a phospholipase A2 from the venom of the Central American coral snake, Micrurus nigrocinctus. Although exploratory in nature, our indicate results showed that only low frequencies of mRNA encoding IgG isotypes, the most relevant isotype for therapeutic purposes, were present in splenocytes of five mice immunized with 6 doses of the two types of toxins over 90 days. Furthermore, analysis of Ig heavy chain transcripts showed that no particular combination of variable (V) and joining (J) gene segments had been selected in the immunization process, as would be expected after a strong humoral immune response to a single antigen. Combined with the titration of toxin-specific antibodies in the sera of immunized mice, these data support the low immunogenicity of three-finger toxins and phospholipases A2 found in M. nigrocinctusvenoms, and highlight the need for future studies analyzing the complexity of antibody responses to toxins at the molecular level.

Hierarchical Clustering Can Identify B Cell Clones with High Confidence in Ig Repertoire Sequencing Data.

Adaptive immunity is driven by the expansion, somatic hypermutation, and selection of B cell clones. Each clone is the progeny of a single B cell responding to Ag, with diversified Ig receptors. These receptors can now be profiled on a large scale by next-generation sequencing. Such data provide a window into the microevolutionary dynamics that drive successful immune responses and the dysregulation that occurs with aging or disease. Clonal relationships are not directly measured, but they must be computationally inferred from these sequencing data. Although several hierarchical clustering-based methods have been proposed, they vary in distance and linkage methods and have not yet been rigorously compared. In this study, we use a combination of human experimental and simulated data to characterize the performance of hierarchical clustering-based methods for partitioning sequences into clones. We find that single linkage clustering has high performance, with specificity, sensitivity, and positive predictive value all >99%, whereas other linkages result in a significant loss of sensitivity. Surprisingly, distance metrics that incorporate the biases of somatic hypermutation do not outperform simple Hamming distance. Although errors were more likely in sequences with short junctions, using the entire dataset to choose a single distance threshold for clustering is near optimal. Our results suggest that hierarchical clustering using single linkage with Hamming distance identifies clones with high confidence and provides a fully automated method for clonal grouping. The performance estimates we develop provide important context to interpret clonal analysis of repertoire sequencing data and allow for rigorous testing of other clonal grouping algorithms.

A Mobile Element in mutS Drives Hypermutation in a Marine Vibrio.

Bacteria face a trade-off between genetic fidelity, which reduces deleterious mistakes in the genome, and genetic innovation, which allows organisms to adapt. Evidence suggests that many bacteria balance this trade-off by modulating their mutation rates, but few mechanisms have been described for such modulation. Following experimental evolution and whole-genome resequencing of the marine bacterium Vibrio splendidus 12B01, we discovered one such mechanism, which allows this bacterium to switch to an elevated mutation rate. This switch is driven by the excision of a mobile element residing in mutS, which encodes a DNA mismatch repair protein. When integrated within the bacterial genome, the mobile element provides independent promoter and translation start sequences for mutS-different from the bacterium's original mutS promoter region-which allow the bacterium to make a functional mutS gene product. Excision of this mobile element rejoins the mutS gene with host promoter and translation start sequences but leaves a 2-bp deletion in the mutS sequence, resulting in a frameshift and a hypermutator phenotype. We further identified hundreds of clinical and environmental bacteria across Betaproteobacteria and Gammaproteobacteria that possess putative mobile elements within the same amino acid motif in mutS In a subset of these bacteria, we detected excision of the element but not a frameshift mutation; the mobile elements leave an intact mutS coding sequence after excision. Our findings reveal a novel mechanism by which one bacterium alters its mutation rate and hint at a possible evolutionary role for mobile elements within mutS in other bacteria. IMPORTANCE: DNA mutations are a double-edged sword. Most mutations are harmful; they can scramble precise genetic sequences honed over thousands of generations. However, in rare cases, mutations also produce beneficial new traits that allow populations to adapt to changing environments. Recent evidence suggests that some bacteria balance this trade-off by altering their mutation rates to suit their environment. To date, however, we know of few mechanisms that allow bacteria to change their mutation rates. We describe one such mechanism, driven by the action of a mobile element, in the marine bacterium Vibrio splendidus 12B01. We also found similar mobile genetic sequences in the mutS genes of many different bacteria, including clinical and agricultural pathogens. These mobile elements might play an as yet unknown role in the evolution of these important bacteria.

Adaptive radiation by waves of gene transfer leads to fine-scale resource partitioning in marine microbes.

Adaptive radiations are important drivers of niche filling, since they rapidly adapt a single clade of organisms to ecological opportunities. Although thought to be common for animals and plants, adaptive radiations have remained difficult to document for microbes in the wild. Here we describe a recent adaptive radiation leading to fine-scale ecophysiological differentiation in the degradation of an algal glycan in a clade of closely related marine bacteria. Horizontal gene transfer is the primary driver in the diversification of the pathway leading to several ecophysiologically differentiated Vibrionaceae populations adapted to different physical forms of alginate. Pathway architecture is predictive of function and ecology, underscoring that horizontal gene transfer without extensive regulatory changes can rapidly assemble fully functional pathways in microbes.

Population genomics of early events in the ecological differentiation of bacteria.

Genetic exchange is common among bacteria, but its effect on population diversity during ecological differentiation remains controversial. A fundamental question is whether advantageous mutations lead to selection of clonal genomes or, as in sexual eukaryotes, sweep through populations on their own. Here, we show that in two recently diverged populations of ocean bacteria, ecological differentiation has occurred akin to a sexual mechanism: A few genome regions have swept through subpopulations in a habitat-specific manner, accompanied by gradual separation of gene pools as evidenced by increased habitat specificity of the most recent recombinations. These findings reconcile previous, seemingly contradictory empirical observations of the genetic structure of bacterial populations and point to a more unified process of differentiation in bacteria and sexual eukaryotes than previously thought.

Merging taxonomy with ecological population prediction in a case study of Vibrionaceae.

We synthesized population structure data from three studies that assessed the fine-scale distribution of Vibrionaceae among temporally and spatially distinct environmental categories in coastal seawater and animals. All studies used a dynamic model (AdaptML) to identify phylogenetically cohesive and ecologically distinct bacterial populations and their predicted habitats without relying on a predefined genetic cutoff or relationships to previously named species. Across the three studies, populations were highly overlapping, displaying similar phylogenetic characteristics (identity and diversity), and were predominantly congruent with taxonomic Vibrio species previously characterized as genotypic clusters by multilocus sequence analysis (MLSA). The environmental fidelity of these populations appears high, with 9 out of 12 reproducibly associating with the same predicted (micro)habitats when similar environmental categories were sampled. Overall, this meta-analysis provides information on the habitat predictability and structure of previously described species, demonstrating that MLSA-based taxonomy can, at least in some cases, serve to approximate ecologically cohesive populations.

DNA phosphorothioation is widespread and quantized in bacterial genomes.

Phosphorothioate (PT) modification of DNA, with sulfur replacing a nonbridging phosphate oxygen, was recently discovered as a product of the dnd genes found in bacteria and archaea. Given our limited understanding of the biological function of PT modifications, including sequence context, genomic frequencies, and relationships to the diversity of dnd gene clusters, we undertook a quantitative study of PT modifications in prokaryotic genomes using a liquid chromatography-coupled tandem quadrupole mass spectrometry approach. The results revealed a diversity of unique PT sequence contexts and three discrete genomic frequencies in a wide range of bacteria. Metagenomic analyses of PT modifications revealed unique ecological distributions, and a phylogenetic comparison of dnd genes and PT sequence contexts strongly supports the horizontal transfer of dnd genes. These results are consistent with the involvement of PT modifications in a type of restriction-modification system with wide distribution in prokaryotes.

Unlocking short read sequencing for metagenomics.

BACKGROUND: Different high-throughput nucleic acid sequencing platforms are currently available but a trade-off currently exists between the cost and number of reads that can be generated versus the read length that can be achieved. METHODOLOGY/PRINCIPAL FINDINGS: We describe an experimental and computational pipeline yielding millions of reads that can exceed 200 bp with quality scores approaching that of traditional Sanger sequencing. The method combines an automatable gel-less library construction step with paired-end sequencing on a short-read instrument. With appropriately sized library inserts, mate-pair sequences can overlap, and we describe the SHERA software package that joins them to form a longer composite read. CONCLUSIONS/SIGNIFICANCE: This strategy is broadly applicable to sequencing applications that benefit from low-cost high-throughput sequencing, but require longer read lengths. We demonstrate that our approach enables metagenomic analyses using the Illumina Genome Analyzer, with low error rates, and at a fraction of the cost of pyrosequencing.

Acute neuroprotective synergy of erythropoietin and insulin-like growth factor I.

Erythropoietin (EPO) and insulin-like growth factor I (IGF-I) are cytokines that inhibit neuronal apoptosis. However, their maximal antiapoptotic effect, even at high concentrations, is observed only when neurons are pretreated for several hours before insult. Here we show that simultaneous administration of EPO and IGF-I (EPO+IGF-I) eliminates the preincubation period required to prevent N-methyl-D-aspartate (NMDA)-induced apoptosis in cultured rat cerebrocortical neurons. The synergistic effect of EPO+IGF-I was mediated, at least in part, by activation of phosphatidylinositol 3-kinase (PI3-K). EPO+IGF-I synergistically activated Akt (protein kinase B), a downstream target of PI3-K, and prevented dephosphorylation of Akt. Overexpression of a dominant interfering form of Akt (dnAkt) abrogated EPO+IGF-I-mediated neuroprotection. EPO+IGF-I treatment did not prevent initial NMDA-induced caspase-3 activation, which was observed within 6 h of insult; however, EPO+IGF-I-treated neurons survived at least 2 days after NMDA insult. These cytokines prevented neuronal apoptosis downstream of caspase activation by facilitating association between X-linked inhibitor of apoptosis protein, an inhibitor of caspase proteolytic activity, and activated caspase-3. These results imply that EPO+IGF-I exert cooperative actions that afford acute neuroprotection via activation of the PI3-K-Akt pathway.