Crohn's disease (CD) is a chronic idiopathic inflammatory intestinal disorder associated with fecal dysbiosis. Fecal microbial transplant (FMT) is a potential therapeutic option for individuals with ...CD based on the hypothesis that changing the fecal dysbiosis could promote less intestinal inflammation.
Nine patients, aged 12 to 19 years, with mild-to-moderate symptoms defined by Pediatric Crohn's Disease Activity Index (PCDAI of 10-29) were enrolled into a prospective open-label study of FMT in CD (FDA IND 14942). Patients received FMT by nasogastric tube with follow-up evaluations at 2, 6, and 12 weeks. PCDAI, C-reactive protein, and fecal calprotectin were evaluated at each study visit.
All reported adverse events were graded as mild except for 1 individual who reported moderate abdominal pain after FMT. All adverse events were self-limiting. Metagenomic evaluation of stool microbiome indicated evidence of FMT engraftment in 7 of 9 patients. The mean PCDAI score improved with patients having a baseline of 19.7 ± 7.2, with improvement at 2 weeks to 6.4 ± 6.6 and at 6 weeks to 8.6 ± 4.9. Based on PCDAI, 7 of 9 patients were in remission at 2 weeks and 5 of 9 patients who did not receive additional medical therapy were in remission at 6 and 12 weeks. No or modest improvement was seen in patients who did not engraft or whose microbiome was most similar to their donor.
This is the first study to demonstrate that FMT for CD may be a possible therapeutic option for CD. Further prospective studies are required to fully assess the safety and efficacy of the FMT in patients with CD.
Patients with cystic fibrosis (CF) have altered fecal microbiomes compared to those of healthy controls. The magnitude of this dysbiosis correlates with measures of CF gastrointestinal (GI) disease, ...including GI inflammation and nutrient malabsorption. However, whether this dysbiosis is caused by mutations in the CFTR gene, the underlying defect in CF, or whether CF-associated dysbiosis augments GI disease was not clear. To test the relationships between CFTR dysfunction, microbes, and intestinal health, we established a germ-free (GF) CF mouse model and demonstrated that CFTR gene mutations are sufficient to alter the GI microbiome. Furthermore, flow cytometric analysis demonstrated that colonized CF mice have increased mesenteric lymph node and spleen TH17+ cells compared with non-CF mice, suggesting that CFTR defects alter adaptive immune responses. Our findings demonstrate that CFTR mutations modulate both the host adaptive immune response and the intestinal microbiome.
Metagenomic sequencing is a promising approach for identifying and characterizing organisms and their functional characteristics in complex, polymicrobial infections, such as airway infections in ...people with cystic fibrosis. These analyses are often hampered, however, by overwhelming quantities of human DNA, yielding only a small proportion of microbial reads for analysis. In addition, many abundant microbes in respiratory samples can produce large quantities of extracellular bacterial DNA originating either from biofilms or dead cells. We describe a method for simultaneously depleting DNA from intact human cells and extracellular DNA (human and bacterial) in sputum, using selective lysis of eukaryotic cells and endonuclease digestion. We show that this method increases microbial sequencing depth and, consequently, both the number of taxa detected and coverage of individual genes such as those involved in antibiotic resistance. This finding underscores the substantial impact of DNA from sources other than live bacteria in microbiological analyses of complex, chronic infection specimens.
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•Human and extracellular bacterial DNA can bias metagenomic sequencing•Hypotonic lysis, endonuclease digestion limit human and extracellular bacterial DNA•Reducing extracellular DNA optimizes metagenomic sequencing of viable bacterial cells•Increased microbial sequencing coverage improves detection of important genes
Nelson et al. describe a method for reducing both human cellular DNA and extracellular DNA (human and bacterial) in a complex respiratory sample using hypotonic lysis and endonuclease digestion. This method increases effective microbial sequencing depth and minimizes bias introduced into subsequent phylogenetic analysis by bacterial extracellular DNA.
Burkholderia pseudomallei, the etiologic agent of human melioidosis, is capable of causing severe acute infection with overwhelming septicemia leading to death. A high rate of recurrent disease ...occurs in adult patients, most often due to recrudescence of the initial infecting strain. Pathogen persistence and evolution during such relapsing infections are not well understood. Bacterial cells present in the primary inoculum and in late infections may differ greatly, as has been observed in chronic disease, or they may be genetically similar. To test these alternative models, we conducted whole-genome comparisons of clonal primary and relapse B. pseudomallei isolates recovered six months to six years apart from four adult Thai patients. We found differences within each of the four pairs, and some, including a 330 Kb deletion, affected substantial portions of the genome. Many of the changes were associated with increased antibiotic resistance. We also found evidence of positive selection for deleterious mutations in a TetR family transcriptional regulator from a set of 107 additional B. pseudomallei strains. As part of the study, we sequenced to base-pair accuracy the genome of B. pseudomallei strain 1026b, the model used for genetic studies of B. pseudomallei pathogenesis and antibiotic resistance. Our findings provide new insights into pathogen evolution during long-term infections and have important implications for the development of intervention strategies to combat recurrent melioidosis.
Acinetobacter baumannii is a Gram-negative bacterial pathogen notorious for causing serious nosocomial infections that resist antibiotic therapy. Research to identify factors responsible for the ...pathogen's success has been limited by the resources available for genome-scale experimental studies. This report describes the development of several such resources for A. baumannii strain AB5075, a recently characterized wound isolate that is multidrug resistant and displays robust virulence in animal models. We report the completion and annotation of the genome sequence, the construction of a comprehensive ordered transposon mutant library, the extension of high-coverage transposon mutant pool sequencing (Tn-seq) to the strain, and the identification of the genes essential for growth on nutrient-rich agar. These resources should facilitate large-scale genetic analysis of virulence, resistance, and other clinically relevant traits that make A. baumannii a formidable public health threat. IMPORTANCE Acinetobacter baumannii is one of six bacterial pathogens primarily responsible for antibiotic-resistant infections that have become the scourge of health care facilities worldwide. Eliminating such infections requires a deeper understanding of the factors that enable the pathogen to persist in hospital environments, establish infections, and resist antibiotics. We present a set of resources that should accelerate genome-scale genetic characterization of these traits for a reference isolate of A. baumannii that is highly virulent and representative of current outbreak strains.
Fecal microbiota transplantation (FMT) is an investigational treatment for diseases thought to involve alterations in the intestinal microbiota including ulcerative colitis (UC). Case reports have ...described therapeutic benefit of FMT in patients with UC, possibly due to changes in the microbiota. We measured the degree to which the transplanted microbiota engraft following FMT in patients with UC using a donor similarity index (DSI).
Seven patients with mild to moderate UC (UC disease activity index scores 3-10) received a single colonoscopic administration of FMT. Metagenomic sequence data from stool were analyzed using an alignment-free comparison tool, to measure the DSI, and a phylogenetic analysis tool, to characterize taxonomic changes. Clinical, endoscopic, histologic, and fecal calprotectin outcome measures were also collected.
One of 5 patients from whom sequencing data were available achieved the primary endpoint of 50% donor similarity at week 4; an additional 2 patients achieved 40% donor similarity. One patient with 40% donor similarity achieved clinical and histologic remission 1 month after FMT. However, these were lost by 2-3 months, and loss correlated with a decrease in DSI. The remaining patients did not demonstrate clinical response or remission. Histology scores improved in all but 1 patient. No patients remained in remission at 3 months after FMT.
Following a single colonoscopic fecal transplant, a DSI of 40-50% is achieved in about two-thirds of recipients. This level of engraftment correlated with a temporary clinical improvement in only 1/5 patients. Larger sample sizes could further validate this method for measuring engraftment, and changes in transplant frequency or method might improve microbiota engraftment and efficacy.
ClinicalTrials.gov NCT01742754.
We previously reported that lagging-strand genes accumulate mutations faster than those encoded on the leading strand in Bacillus subtilis . Although we proposed that orientation-specific encounters ...between replication and transcription underlie this phenomenon, the mechanism leading to the increased mutagenesis of lagging-strand genes remained unknown. Here, we report that the transcription-dependent and orientation-specific differences in mutation rates of genes require the B. subtilis Y-family polymerase, PolY1 ( yqjH ). We find that without PolY1, association of the replicative helicase, DnaC, and the recombination protein, RecA, with lagging-strand genes increases in a transcription-dependent manner. These data suggest that PolY1 promotes efficient replisome progression through lagging-strand genes, thereby reducing potentially detrimental breaks and single-stranded DNA at these loci. Y-family polymerases can alleviate potential obstacles to replisome progression by facilitating DNA lesion bypass, extension of D-loops, or excision repair. We find that the nucleotide excision repair (NER) proteins UvrA, UvrB, and UvrC, but not RecA, are required for transcription-dependent asymmetry in mutation rates of genes in the two orientations. Furthermore, we find that the transcription-coupling repair factor Mfd functions in the same pathway as PolY1 and is also required for increased mutagenesis of lagging-strand genes. Experimental and SNP analyses of B. subtilis genomes show mutational footprints consistent with these findings. We propose that the interplay between replication and transcription increases lesion susceptibility of, specifically, lagging-strand genes, activating an Mfd-dependent error-prone NER mechanism. We propose that this process, at least partially, underlies the accelerated evolution of lagging-strand genes.
Significance Replication and transcription can occur concurrently and use the same DNA template. This can cause genomic instability such as common fragile site instability in eukaryotes, and accelerated evolution of lagging-strand genes in bacteria. Here, we report an underlying mechanism that increases mutation rates of lagging-strand genes in Bacillus subtilis. We find that this process is mediated through the transcription-dependent activity of the Y-family polymerase, PolY1, in transcription-coupled nucleotide excision repair. We find that PolY1, likely through this mechanism, reduces the potentially problematic impacts of specifically lagging-strand transcription on replisome progression and genomic instability. This work shows that gene orientation, together with transcription, can cause differential activities of repair mechanisms, specifically increasing mutagenesis in lagging-strand genes.
GOAL:To determine the effect of the specific carbohydrate diet (SCD) on active inflammatory bowel disease (IBD).
BACKGROUND:IBD is a chronic idiopathic inflammatory intestinal disorder associated ...with fecal dysbiosis. Diet is a potential therapeutic option for IBD based on the hypothesis that changing the fecal dysbiosis could decrease intestinal inflammation.
STUDY:Pediatric patients with mild to moderate IBD defined by pediatric Crohn’s disease activity index (PCDAI 10-45) or pediatric ulcerative colitis activity index (PUCAI 10-65) were enrolled into a prospective study of the SCD. Patients started SCD with follow-up evaluations at 2, 4, 8, and 12 weeks. PCDAI/PUCAI, laboratory studies were assessed.
RESULTS:Twelve patients, ages 10 to 17 years, were enrolled. Mean PCDAI decreased from 28.1±8.8 to 4.6±10.3 at 12 weeks. Mean PUCAI decreased from 28.3±23.1 to 6.7±11.6 at 12 weeks. Dietary therapy was ineffective for 2 patients while 2 individuals were unable to maintain the diet. Mean C-reactive protein decreased from 24.1±22.3 to 7.1±0.4 mg/L at 12 weeks in Seattle Cohort (nL<8.0 mg/L) and decreased from 20.7±10.9 to 4.8±4.5 mg/L at 12 weeks in Atlanta Cohort (nL<4.9 mg/L). Stool microbiome analysis showed a distinctive dysbiosis for each individual in most prediet microbiomes with significant changes in microbial composition after dietary change.
CONCLUSIONS:SCD therapy in IBD is associated with clinical and laboratory improvements as well as concomitant changes in the fecal microbiome. Further prospective studies are required to fully assess the safety and efficacy of dietary therapy in patients with IBD.
Most infants with cystic fibrosis (CF) have pancreatic exocrine insufficiency that results in nutrient malabsorption and requires oral pancreatic enzyme replacement. Newborn screening for CF has ...enabled earlier diagnosis, nutritional intervention and enzyme replacement for these infants, allowing most infants with CF to achieve their weight goals by 12 months of age
. Nevertheless, most infants with CF continue to have poor linear growth during their first year of life
. Although this early linear growth failure is associated with worse long-term respiratory function and survival
, the determinants of body length in infants with CF have not been defined. Several characteristics of the CF gastrointestinal (GI) tract, including inflammation, maldigestion and malabsorption, may promote intestinal dysbiosis
. As GI microbiome activities are known to affect endocrine functions
, the intestinal microbiome of infants with CF may also impact growth. We identified an early, progressive fecal dysbiosis that distinguished infants with CF and low length from infants with CF and normal length. This dysbiosis included altered abundances of taxa that perform functions that are important for GI health, nutrient harvest and growth hormone signaling, including decreased abundance of Bacteroidetes and increased abundance of Proteobacteria. Thus, the GI microbiota represent a potential therapeutic target for the correction of low linear growth in infants with CF.
While considerable research has focused on the properties of individual bacteria, relatively little is known about how microbial interspecies interactions alter bacterial behaviors and pathogenesis. ...Staphylococcus aureus frequently coinfects with other pathogens in a range of different infectious diseases. For example, coinfection by S. aureus with Pseudomonas aeruginosa occurs commonly in people with cystic fibrosis and is associated with higher lung disease morbidity and mortality. S. aureus secretes numerous exoproducts that are known to interact with host tissues, influencing inflammatory responses. The abundantly secreted S. aureus staphylococcal protein A (SpA) binds a range of human glycoproteins, immunoglobulins, and other molecules, with diverse effects on the host, including inhibition of phagocytosis of S. aureus cells. However, the potential effects of SpA and other S. aureus exoproducts on coinfecting bacteria have not been explored. Here, we show that S. aureus-secreted products, including SpA, significantly alter two behaviors associated with persistent infection. We found that SpA inhibited biofilm formation by specific P. aeruginosa clinical isolates, and it also inhibited phagocytosis by neutrophils of all isolates tested. Our results indicate that these effects were mediated by binding to at least two P. aeruginosa cell surface structures-type IV pili and the exopolysaccharide Psl-that confer attachment to surfaces and to other bacterial cells. Thus, we found that the role of a well-studied S. aureus exoproduct, SpA, extends well beyond interactions with the host immune system. Secreted SpA alters multiple persistence-associated behaviors of another common microbial community member, likely influencing cocolonization and coinfection with other microbes.
Bacteria rarely exist in isolation, whether on human tissues or in the environment, and they frequently coinfect with other microbes. However, relatively little is known about how microbial interspecies interactions alter bacterial behaviors and pathogenesis. We identified a novel interaction between two bacterial species that frequently infect together-Staphylococcus aureus and Pseudomonas aeruginosa We show that the S. aureus-secreted protein staphylococcal protein A (SpA), which is well-known for interacting with host targets, also binds to specific P. aeruginosa cell surface molecules and alters two persistence-associated P. aeruginosa behaviors: biofilm formation and uptake by host immune cells. Because S. aureus frequently precedes P. aeruginosa in chronic infections, these findings reveal how microbial community interactions can impact persistence and host interactions during coinfections.
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