Stool sampling and DNA isolation kits affect DNA quality and bacterial composition following 16S rRNA gene sequencing using MiSeq Illumina platform

Comparison of Fecal DNA Extraction Kits for the Giant Panda (Ailuropoda melanoleuca) by Short Tandem Repeat Genotype Analysis

Genetic analysis of short tandem repeat (STR) loci using noninvasive fecal samples is currently the most widely used method in genetic surveys of giant pandas (Ailuropoda melanoleuca). However, low-quality fecal DNA obtained from fecal samples may affect the accuracy of short tandem repeat (STR) genotyping results and pose a challenge to accurately identify individuals. The aim of this study was thus to compare the efficiency of DNA extraction kits in obtaining high-quality fecal host DNA from giant panda fecal samples. In this study, six commercial kits widely used in fecal DNA extraction, the QIAamp Fast DNA Stool Mini Kit (Q kit), Beaver Beads Stool DNA Kit (H kit), Mag-MK Soil & Stool Genome DNA Extraction kit (S kit), Magnetic Soil And Stool DNA Kit (T kit), E.Z.N.A Mag-Bind Stool DNA Kit (O kit) and Mag Beads Fast DNA Kit for Feces (M kit) were compared. Fecal DNA concentration and purity were measured, and STR genotyping was performed using blood and fecal DNA from captive giant pandas to compare the genotype matches at 11 STR loci. Our results show that the most efficient extraction kits were the Q and T kits, and the Q kit had a greater ability to remove PCR inhibitors than other kits. Careful selection of DNA extraction kits is required to achieve optimal genotyping accuracy across different STR genotyping systems. For STR genotyping systems with smaller PCR product sizes (< 200 bp, such as GPL-29, GP-08, GP-01, Panda-40 and Panda-05), all six kits demonstrated high genotype matching rates (GMR > 80%). In contrast, for STR genotyping systems with longer PCR product sizes (> 200 bp), the choice of DNA extraction kit significantly influenced GMR, with the H kit and O kit performing well for gpy-5 but the Q kit and O kit being less suitable for GPL-08.

Using short-read 16S rRNA sequencing of multiple variable regions to generate high-quality results to a species level

Introduction

Short-read amplicon sequencing studies have typically focused on 1-2 variable regions of the 16S rRNA gene. Species-level resolution is limited in these studies, as each variable region enables the characterisation of a different subsection of the microbiome. Although long-read sequencing techniques can take advantage of all 9 variable regions by sequencing the entire 16S rRNA gene, short-read sequencing has remained a commonly used approach in 16S rRNA research. This work assessed the feasibility of accurate species-level resolution and reproducibility using a relatively new sequencing kit and bioinformatics pipeline developed for short-read sequencing of multiple variable regions of the 16S rRNA gene. In addition, we evaluated the potential impact of different sample collection methods on our outcomes.

Methods

Using xGen™ 16S Amplicon Panel v2 kits, sequencing of all 9 variable regions of the 16S rRNA gene was carried out on an Illumina MiSeq platform. Mock cells and mock DNA for 8 bacterial species were included as extraction and sequencing controls respectively. Within-run and between-run replicate samples, and pairs of stool and rectal swabs collected at 0-5 weeks from the same infants, were incorporated. Observed relative abundances of each species were compared to theoretical abundances provided by ZymoBIOMICS. Paired Wilcoxon rank sum tests and distance-based intraclass correlation coefficients were used to statistically compare alpha and beta diversity measures, respectively, for pairs of replicates and stool/rectal swab sample pairs.

Results

Using multiple variable regions of the 16S ribosomal Ribonucleic Acid (rRNA) gene, we found that we could accurately identify taxa to a species level and obtain highly reproducible results at a species level. Yet, the microbial profiles of stool and rectal swab sample pairs differed substantially despite being collected concurrently from the same infants.

Conclusion

This protocol provides an effective means for studying infant gut microbial samples at a species level. However, sample collection approaches need to be accounted for in any downstream analysis.

Impact of antibiotic prophylaxis on gut microbiota in colorectal surgery: insights from an Eastern European stewardship study

Introduction

Antibiotic overuse is driving a global rise in antibiotic resistance, highlighting the need for robust antimicrobial stewardship (AMS) initiatives to improve prescription practices. While antimicrobials are essential for treating sepsis and preventing surgical site infections (SSIs), they can inadvertently disrupt the gut microbiota, leading to postoperative complications. Treatment methods vary widely across nations due to differences in drug choice, dosage, and therapy duration, affecting antibiotic resistance rates, which can reach up to 51% in some countries. In Romania and the Republic of Moldova, healthcare practices for surgical antibiotic prophylaxis differ significantly despite similarities in genetics, culture, and diet. Romania's stricter healthcare regulations result in more standardized antibiotic protocols, whereas Moldova's limited healthcare funding leads to less consistent practices and greater variability in treatment outcomes.

Methods

This study presents the results of a prospective cross-border investigation involving 86 colorectal cancer patients from major oncological hospitals in Romania and Moldova. We analyzed fecal samples collected from patients before and 7 days post-antibiotic treatment, focusing on the V3-V4 region of the 16S rRNA gene.

Results

Our findings indicate that inconsistent antibiotic prophylaxis policies-varying in type, dosage, or therapy duration-significantly impacted the gut microbiota and led to more frequent dysbiosis compared to stricter prophylactic antibiotic practices (single dose, single product, limited time).

Discussion

We emphasize the need for standardized antibiotic prophylaxis protocols to minimize dysbiosis and its associated risks, promoting more effective antimicrobial use, particularly in low- and middle-income countries (LMICs).

Effects of non-pharmacological interventions on gut microbiota and intestinal permeability in older adults: A systematic review: Non-pharmacological interventions on gut microbiota/barrier

This systematic review appraised previous findings of non-pharmacological interventions on gut microbiota and/ or intestinal permeability in older adults. A literature search was performed using PubMed, Scopus, ScienceDirect and the Cochrane Library. Relevant studies were shortlisted based on the inclusion and exclusion criteria, and evaluated for risks of bias using the "Cochrane Collaboration's Risk of Bias 2" and the "NIH Quality Assessment Tool for Before-After (Pre-Post) Studies with No Control Group". The primary outcomes were the effects of non-pharmacological interventions on gut microbiota diversity and composition, and intestinal permeability in older adults. Out of 85,114 studies, 38 were shortlisted. Generally, the non-pharmacological interventions were beneficial against dysbiosis and the leaky gut in older adults. Considering specific interventions with two or more studies that reported consistent outcomes, a pattern was observed amongst the Mediterranean diet (MD), polyphenol-rich (PR) diet and supplements (i.e., probiotics, prebiotics and synbiotics). As for the other interventions, the very few studies that have been conducted did not allow a strong conclusion to be made just yet. The MD (single and multidomain interventions) restored gut microbiota by increasing species richness (alpha diversity) and reduced intestinal permeability (zonulin) and inflammation (CRP). The PR diet only showed slight changes in the gut microbiota but improved the gut barrier by reducing zonulin, CRP and IL-6. Probiotics, prebiotics and synbiotics increased the genus Bifidobacterium spp. which are considered beneficial bacteria. This review has uncovered insights into the relationship between gut microbiota and intestinal epithelial barriers of specific non-pharmacological interventions in older adults.

A Comparison of Three Automated Nucleic Acid Extraction Systems for Human Stool Samples

Automated nucleic acid extractors are useful instruments for the high-throughput processing of bio-samples and are expected to improve research throughput in addition to decreased inter-sample variability inherent to manual processing. We evaluated three commercial nucleic acid extractors Bioer GenePure Pro (Bioer Technology, Hangzhou, China), Maxwell RSC 16 (Promega Corporation, Madison, WI, USA), and KingFisher Apex (ThermoFisher Scientific, Waltham, MA, USA) based on their DNA yield, DNA purity, and 16S rRNA gene amplicon results using both human fecal samples and a mock community (ZymoBIOMICS Microbial Community Standard (Zymo Research Corp., Irvine, CA, USA)). Bead-beating provided incremental yield to effectively lyse and extract DNA from stool samples compared to lysis buffer alone. Differential abundance analysis and comparison of prevalent bacterial species revealed a greater representation of Gram-positive bacteria in samples subjected to mechanical lysis, regardless of sample type. All three commercial extractors had differences in terms of yield, inter-sample variability, and subsequent sequencing readouts, which we subsequently share in the paper and believe are significant considerations for all researchers undertaking human fecal microbiota research.

Advancements in analytical methods for studying the human gut microbiome

Background

The human gut microbiome, a complex ecosystem of microorganisms, plays a crucial role in maintaining human health. Perturbations in its composition are linked to a wide range of health conditions.

Analytical techniques

Researchers employ various techniques to study the gut microbiome, each having its own strengths and limitations. Polymerase chain reaction (PCR) is highly sensitive but dependent on the quality of DNA extraction. Next-generation sequencing (NGS) is powerful but can be costly and requires extensive data analysis. Furthermore, the accuracy of NGS results also depends heavily on the quality of the DNA extraction process. Culture methods, while useful, are biased and time-consuming. Fluorescence in situ hybridization (FISH) excels in visualizing specific microbial populations and is the only method capable of providing in situ information. However, until recently, FISH was heavily reliant on human interpretation of digital photomicrographs, limiting its application in high-throughput strategies. Additionally, the sensitivity of FISH is restricted by the number of cells visualized.

Conclusion

Understanding the strengths and weaknesses of these methods is essential for drawing robust conclusions in microbiome research.

Protective effect of gut microbiota restored by fecal microbiota transplantation in a sepsis model in juvenile mice

Introduction

Restoring a balanced, healthy gut microbiota through fecal microbiota transplantation (FMT) has the potential to be a treatment option for sepsis, despite the current lack of evidence. This study aimed to investigate the effect of FMT on sepsis in relation to the gut microbiota through a sepsis model in juvenile mice.

Methods

Three-week-old male mice were divided into three groups: the antibiotic treatment (ABX), ABX-FMT, and control groups. The ABX and ABX-FMT groups received antibiotics for seven days. FMT was performed through oral gavage in the ABX-FMT group over the subsequent seven days. On day 14, all mice underwent cecal ligation and puncture (CLP) to induce abdominal sepsis. Blood cytokine levels and the composition of fecal microbiota were analyzed, and survival was monitored for seven days post-CLP.

Results

Initially, the fecal microbiota was predominantly composed of the phyla Bacteroidetes and Firmicutes. After antibiotic intake, an extreme predominance of the class Bacilli emerged. FMT successfully restored antibiotic-induced fecal dysbiosis. After CLP, the phylum Bacteroidetes became extremely dominant in the ABX-FMT and control groups. Alpha diversity of the microbiota decreased after antibiotic intake, was restored after FMT, and decreased again following CLP. In the ABX group, the concentrations of interleukin-1β (IL-1β), IL-2, IL-6, IL-10, granulocyte macrophage colony-stimulating factor, tumor necrosis factor-α, and C-X-C motif chemokine ligand 1 increased more rapidly and to a higher degree compared to other groups. The survival rate in the ABX group was significantly lower (20.0%) compared to other groups (85.7%).

Conclusion

FMT-induced microbiota restoration demonstrated a protective effect against sepsis. This study uniquely validates the effectiveness of FMT in a juvenile mouse sepsis model, offering potential implications for clinical research in critically ill children.

Impact of intrapartum antibiotic prophylaxis on the oral and fecal bacteriomes of children in the first week of life

Intrapartum antibiotic prophylaxis (IAP) is commonly used during C-section delivery and in Group B Streptococcus-positive women before vaginal delivery. Here, we primarily aimed to investigate the effect of IAP on the neonatal oral and fecal bacteriomes in the first week of life. In this preliminary study, maternal and neonatal oral swabs and neonatal fecal (meconium and transitional stool) swabs were selected from a pool of samples from healthy mother-neonate pairs participating in the pilot phase of CELSPAC: TNG during their hospital stay. The DNA was extracted and bacteriome profiles were determined by 16S rRNA amplicon sequencing (Illumina). In the final dataset, 33 mother-neonate pairs were exposed to antibiotics during C-section or vaginal delivery (cases; +IAP) and the vaginal delivery without IAP (controls, -IAP) took place in 33 mother-neonate pairs. Differences in alpha diversity (Shannon index, p=0.01) and bacterial composition (PERMANOVA, p<0.05) between the +IAP and -IAP groups were detected only in neonatal oral samples collected ≤48 h after birth. No significant differences between meconium bacteriomes of the +IAP and -IAP groups were observed (p>0.05). However, the IAP was associated with decreased alpha diversity (number of amplicon sequence variants, p<0.001), decreased relative abundances of the genera Bacteroides and Bifidobacterium, and increased relative abundances of genera Enterococcus and Rothia (q<0.01 for all of them) in transitional stool samples. The findings of this study suggest that exposure to IAP may significantly influence the early development of the neonatal oral and gut microbiomes. IAP affected the neonatal oral bacteriome in the first two days after birth as well as the neonatal fecal bacteriome in transitional stool samples. In addition, it highlights the necessity for further investigation into the potential long-term health impacts on children.

Optimization of the Method for Isolating Bacterial DNA from the Aboveground Part of Lettuce

Developing an effective method for isolating bacterial genetic material from plants is a relatively challenging task and often does not yield adequately prepared material for further analyses. Previous studies often overlook connections, primarily focusing on laboratory investigations. With advancements in high-throughput sequencing techniques, we can now revisit and delve deeper into these interactions. Our study focuses on the initial phase of these investigations: genetic material isolation. Extracting bacterial DNA from aboveground plant parts, known as the phyllosphere, poses a significant challenge due to plant-derived contaminants. Existing isolation protocols frequently yield inconsistent results, necessitating continuous refinement and optimization. In our study, we developed an effective isolation protocol employing mechanical-chemical lysis, sonication, and membrane filtration. This approach yielded high-quality DNA at a concentration of 38.08 ng/µL, suitable for advanced sequencing applications. Our results underscore the effectiveness and necessity of these methods for conducting comprehensive microbiological analyses. Furthermore, our research not only lays the groundwork for further studies on lettuce microbiota, but also highlights the potential for utilizing our developed protocol in investigating other plants and their microbiomes.

Using short-read 16S rRNA sequencing of multiple variable regions to generate high-quality results to a species level

Introduction

Short-read amplicon sequencing studies have typically focused on 1-2 variable regions of the 16S rRNA gene. Species-level resolution is limited in these studies, as each variable region enables the characterisation of a different subsection of the microbiome. Although long-read sequencing techniques take advantage of all 9 variable regions by sequencing the entire 16S rRNA gene, they are substantially more expensive. This work assessed the feasibility of accurate species-level resolution and reproducibility using a relatively new sequencing kit and bioinformatics pipeline developed for short-read sequencing of multiple variable regions of the 16S rRNA gene. In addition, we evaluated the potential impact of different sample collection methods on our outcomes.

Methods

Using xGen™ 16S Amplicon Panel v2 kits, sequencing of all 9 variable regions of the 16S rRNA gene was carried out on an Illumina MiSeq platform. Mock cells and mock DNA for 8 bacterial species were included as extraction and sequencing controls respectively. Within-run and between-run replicate samples, and pairs of stool and rectal swabs collected at 0-5 weeks from the same participants, were incorporated. Observed relative abundances of each species were compared to theoretical abundances provided by ZymoBIOMICS. Paired Wilcoxon rank sum tests and distance-based intraclass correlation coefficients were used to statistically compare alpha and beta diversity measures, respectively, for pairs of replicates and stool/rectal swab sample pairs.

Results

Using multiple variable regions of the 16S ribosomal Ribonucleic Acid (rRNA) gene, we found that we could accurately identify taxa to a species level and obtain highly reproducible results at a species level. Yet, the microbial profiles of stool and rectal swab sample pairs differed substantially despite being collected concurrently from the same infants.

Conclusion

This protocol provides an effective means for studying infant gut microbial samples at a species level. However, sample collection approaches need to be accounted for in any downstream analysis.

Moringa oleifera leaf improves meat quality by modulating intestinal microbes in white feather broilers

Moringa oleifera addition to animal diets can improve the growth performance, intestinal health, and immunity of animals, without adverse effects. We investigated the effects of Moringa oleifera on the growth performance, meat quality, and intestinal health of broilers. Moringa oleifera and fermented Moringa oleifera could improve the flesh color and breast muscle tenderness of broilers (p < 0.05). The contents of essential amino acids, unsaturated fatty acids, ΣMUFA, P/S and n-3 ratio in breast muscle of broilers were dose-increased, and the effect of fermented Moringa oleifera was better. Moringa oleifera and fermented Moringa oleifera regulated chicken flavor metabolism by increasing the relative abundance and Short-chain fatty acid (SCFA) contents of Bacteroides, Spirillum, and lactic acid bacteria. Overall, supplementation with 1 % fermented Moringa oleifera can significantly increase essential amino acid and unsaturated fatty acid contents in broilers and participate in the synthesis and transformation of amino acids and fatty acids regulated by beneficial bacteria.

Benchmarking DNA isolation methods for marine metagenomics

Metagenomics is a powerful tool to study marine microbial communities. However, obtaining high-quality environmental DNA suitable for downstream sequencing applications is a challenging task. The quality and quantity of isolated DNA heavily depend on the choice of purification procedure and the type of sample. Selection of an appropriate DNA isolation method for a new type of material often entails a lengthy trial and error process. Further, each DNA purification approach introduces biases and thus affects the composition of the studied community. To account for these problems and biases, we systematically investigated efficiency of DNA purification from three types of samples (water, sea sediment, and digestive tract of a model invertebrate Magallana gigas) with eight commercially available DNA isolation kits. For each kit-sample combination we measured the quantity of purified DNA, extent of DNA fragmentation, the presence of PCR-inhibiting contaminants, admixture of eukaryotic DNA, alpha-diversity, and reproducibility of the resulting community composition based on 16S rRNA amplicons sequencing. Additionally, we determined a "kitome", e.g., a set of contaminating taxa inherent for each type of purification kit used. The resulting matrix of evaluated parameters allows one to select the best DNA purification procedure for a given type of sample.

Comparison of four DNA extraction methods for 16s rRNA microbiota profiling of human faecal samples

OBJECTIVE

Growth in large population-based studies assessing contributions of the gut microbiota to health and disease requires high-throughput sample processing and analysis methods. This study assessed the impact that modifications to a commercially available magnetic bead based, semi-automated DNA extraction kit had on determination of microbial composition, relative to an established in-house method involving a combination of mechanical and chemical lysis. DNA was extracted from faecal samples from healthy adults (n = 12; 34-69 years), microbial composition was determined by V3-V4 16s rRNA sequencing and compared between extraction methods.

RESULTS

Diversity metrics did not differ between extraction methods. Differences in the relative abundance of key phyla, including a significantly lower abundance of the Firmicutes (p = 0.004) and higher relative abundance of the Bacteroidetes (p = 0.005) and Proteobacteria (p = 0.008) phyla were noted where the DNA extraction did not include additional chemical and mechanical lysis. Principal coordinate analysis of family and genera level data also suggested a potential for sample pre-processing to impact microbial composition. Observations of the potential for skewed microbial composition profiles from samples prepared using a semi-automated DNA extraction kit without additional sample pre-processing highlights a need for consideration of standardisation of methodological approaches to increase the comparability of microbial compositional data.

Pragmatic Considerations When Extracting DNA for Metagenomics Analyses of Clinical Samples

Microbiome analyses are essential for understanding microorganism composition and diversity, but interpretation is often challenging due to biological and technical variables. DNA extraction is a critical step that can significantly bias results, particularly in samples containing a high abundance of challenging-to-lyse microorganisms. Taking into consideration the distinctive microenvironments observed in different bodily locations, our study sought to assess the extent of bias introduced by suboptimal bead-beating during DNA extraction across diverse clinical sample types. The question was whether complex targeted extraction methods are always necessary for reliable taxonomic abundance estimation through amplicon sequencing or if simpler alternatives are effective for some sample types. Hence, for four different clinical sample types (stool, cervical swab, skin swab, and hospital surface swab samples), we compared the results achieved from extracting targeted manual protocols routinely used in our research lab for each sample type with automated protocols specifically not designed for that purpose. Unsurprisingly, we found that for the stool samples, manual extraction protocols with vigorous bead-beating were necessary in order to avoid erroneous taxa proportions on all investigated taxonomic levels and, in particular, false under- or overrepresentation of important genera such as Blautia, Faecalibacterium, and Parabacteroides. However, interestingly, we found that the skin and cervical swab samples had similar results with all tested protocols. Our results suggest that the level of practical automation largely depends on the expected microenvironment, with skin and cervical swabs being much easier to process than stool samples. Prudent consideration is necessary when extending the conclusions of this study to applications beyond rough estimations of taxonomic abundance.

Human gut microbiome: A primer for the clinician

The human host gets tremendously influenced by a genetically and phenotypically distinct and heterogeneous constellation of microbial species-the human microbiome-the gut being one of the most densely populated and characterized site for these organisms. Microbiome science has advanced rapidly, technically with respect to the analytical methods and biologically with respect to its mechanistic influence in health and disease states. A clinician conducting a microbiome study should be aware of the nuances related to microbiome research, especially with respect to the technical and biological factors that can influence the interpretation of research outcomes. Hence, this review is an attempt to detail these aspects of the human gut microbiome, with emphasis on its determinants in a healthy state.

Maternal vaginal microbiome composition does not affect development of the infant gut microbiome in early life

Birth mode has been implicated as a major factor influencing neonatal gut microbiome development, and it has been assumed that lack of exposure to the maternal vaginal microbiome is responsible for gut dysbiosis among caesarean-delivered infants. Consequently, practices to correct dysbiotic gut microbiomes, such as vaginal seeding, have arisen while the effect of the maternal vaginal microbiome on that of the infant gut remains unknown. We conducted a longitudinal, prospective cohort study of 621 Canadian pregnant women and their newborn infants and collected pre-delivery maternal vaginal swabs and infant stool samples at 10-days and 3-months of life. Using cpn60-based amplicon sequencing, we defined vaginal and stool microbiome profiles and evaluated the effect of maternal vaginal microbiome composition and various clinical variables on the development of the infant stool microbiome. Infant stool microbiomes showed significant differences in composition by delivery mode at 10-days postpartum; however, this effect could not be explained by maternal vaginal microbiome composition and was vastly reduced by 3 months. Vaginal microbiome clusters were distributed across infant stool clusters in proportion to their frequency in the overall maternal population, indicating independence of the two communities. Intrapartum antibiotic administration was identified as a confounder of infant stool microbiome differences and was associated with lower abundances of Escherichia coli, Bacteroides vulgatus, Bifidobacterium longum and Parabacteroides distasonis. Our findings demonstrate that maternal vaginal microbiome composition at delivery does not affect infant stool microbiome composition and development, suggesting that practices to amend infant stool microbiome composition focus factors other than maternal vaginal microbes.

Comparison of four DNA extraction kits efficiency for 16SrDNA microbiota profiling of diverse human samples

Aim: The current study investigated the performance of 4 widely used DNA extraction kits using different types of high (stool) and low biomass samples (chyme, broncho alveolar lavage and sputum). Methods: Qiagen Powerfecal Pro DNA kit, Macherey Nucleospin Soil kit, Macherey Nucleospin Tissue Kit and MagnaPure LC DNA isolation kit III were evaluated in terms of DNA quantity, quality, diversity and composition profiles. Results: The quantity and quality of DNA varied among the four kits. The microbiota of the stool samples showed similar diversity and compositional profiles for the 4 kits. Conclusion: Despite differences in DNA quality and quantity, the 4 kits yielded similar results for stool samples, while all kits were not sensitive enough for low biomass samples.

Optimizing DNA Extraction from Pediatric Stool for Diagnosis of Tuberculosis and Use in Next-Generation Sequencing Applications

The WHO has endorsed the use of stool samples for diagnosis of tuberculosis (TB) in children, and targeted next-generation sequencing (tNGS) of stool has been shown to support diagnosis and provide information about drug susceptibility (DS). Optimizing extraction of DNA from stool for sequencing is critical to ensure high diagnostic sensitivity and accurate DS information. Human stool samples were spiked with various concentrations of Mycobacterium bovis bacillus Calmette-Guérin (BCG), and DNA was extracted from the samples using four different DNA extraction kits. Each sample was subjected to quantitative PCR for identifying Mycobacterium tuberculosis complex bacteria and underwent further analysis to assess the overall DNA yield, fragment length, and purity. This same process was performed with 10 pediatric participants diagnosed with pulmonary TB, and the samples underwent tNGS. The FastDNA spin kit for soil showed the best results on model samples spiked with known quantities of BCG, compared to the other extraction methods evaluated. For clinical samples, the FastDNA and PowerFecal Pro DNA (PowerFecal) kits both showed an increase in the overall DNA quantity, M. tuberculosis-specific DNA quantity, and successful targeted sequencing when testing was performed on stool samples, compared to the two other kits. Three samples extracted via PowerFecal and three samples extracted via FastDNA (from different patients) provided successful sequencing data, with an average depth of coverage of the rpoB region for FastDNA of 298 (range, 107 to 550) and for PowerFecal of 310 (range, 182 to 474), results that were comparable to one another (P = 0.946). The PowerFecal Pro and FastDNA spin kits were superior for extracting DNA from pediatric stool samples for tNGS. IMPORTANCE This is the first study to compare Mycobacterium tuberculosis DNA extraction techniques from pediatric stool samples for use with sequencing technologies. It provides an important starting point for other researchers to isolate quality DNA for this purpose to further the field and to continue to optimize protocols and approaches.

Microbiome-Based Stain Analyses in Crime Scenes

Recent advances in next-generation sequencing technologies (NGS) coupled with machine learning have demonstrated the potential of microbiome-based analyses in applied areas such as clinical diagnostics and forensic sciences. Particularly in forensics, microbial markers in biological stains left at a crime scene can provide valuable information for the reconstruction of crime scene cases, as they contain information on bodily origin, the time since deposition, and donor(s) of the stain. Importantly, microbiome-based analyses provide a complementary or an alternative approach to current methods when these are limited or not feasible. Despite the promising results from recent research, microbiome-based stain analyses are not yet employed in routine casework. In this review, we highlight the two main gaps that need to be addressed before we can successfully integrate microbiome-based analyses in applied areas with a special focus on forensic casework: one is a comprehensive assessment of the method's strengths and limitations, and the other is the establishment of a standard operating procedure. For the latter, we provide a roadmap highlighting key decision steps and offering laboratory and bioinformatic workflow recommendations, while also delineating those aspects that require further testing. Our goal is to ultimately facilitate the streamlining of microbiome-based analyses within the existing forensic framework to provide alternate lines of evidence, thereby improving the quality of investigations.

Detection of cytomegalovirus (CMV) by digital PCR in stool samples for the non-invasive diagnosis of CMV gastroenteritis

Background

CMV gastroenteritis is common in patients receiving allogeneic hematopoietic stem cell transplantation and it is difficult to distinguish from acute graft-versus-host disease (aGvHD), which has very similar symptoms but needs quite different treatment. CMV gastroenteritis is caused by local infection or reactivation of CMV in the gastrointestinal tract while aGvHD is due to immune rejection. The gold standard of diagnosis of CMV gastroenteritis and aGvHD is gastrointestinal biopsy under endoscopy, which is invasive and can potentially lead to severe side effects. Stool samples testing with quantitative polymerase chain reaction (qPCR) may be an alternative, while the application in trace level measurements and precision are not all satisfactory enough in reported research.

Methods

In this study, we designed a novel method that extracted the cell free DNA (cfDNA) from the fecal supernatant to perform digital PCR (dPCR) for the detection of CMV, analyzed the performance and compared it with the total DNA extracted by the current procedure.

Results

Twenty-two paired stool samples using two DNA extraction methods proved that the cfDNA extraction method had markedly higher DNA concentrations and control gene copy number, suggesting that cfDNA may be more informative and more useful for the detection of CMV DNA segment. The dPCR approach in detecting CMV DNA segment also exhibit good linearity (R2 = 0.997) and higher sensitivity (limit of detection at 50% was 3.534 copies/μL). Eighty-two stool samples from 44 immunocompromised patients were analyzed, CMV-positive rate was 28%, indicating that more than one-quarter of the gastrointestinal symptoms within these patients may be caused by CMV infection or reactivation.

Conclusion

The combined results suggest that detection of CMV by dPCR in cfDNA of stool supernatant is a powerful method to identify CMV gastroenteritis and helps in clinical treatment decision making.

Bringing pharmacomicrobiomics to the clinic through well-designed studies

Pharmacomicrobiomic studies investigate drug-microbiome interactions, such as the effect of microbial variation on drug response and disposition. Studying and understanding the interactions between the gut microbiome and drugs is becoming increasingly relevant to clinical practice due to its potential for avoiding adverse drug reactions or predicting variability in drug response. The highly variable nature of the human microbiome presents significant challenges to assessing microbes' influence. Studies aiming to explore drug-microbiome interactions should be well-designed to account for variation in the microbiome over time and collect data on confounders such as diet, disease, concomitant drugs, and other environmental factors. Here, we assemble a set of important considerations and recommendations for the methodological features required for performing a pharmacomicrobiomic study in humans with a focus on the gut microbiome. Consideration of these factors enable discovery, reproducibility, and more accurate characterization of the relationships between a given drug and the microbiome. Furthermore, appropriate interpretation and dissemination of results from well-designed studies will push the field closer to clinical relevance and implementation.

Microbiome analysis: An emerging forensic investigative tool

Microbial diversity's potential has been investigated in medical and therapeutic studies throughout the last few decades. However, its usage in forensics is increasing due to its effectiveness in circumstances when traditional approaches fail to provide a decisive opinion or are insufficient in forming a concrete opinion. The application of human microbiome may serve in detecting the type of stains of saliva and vaginal fluid, as well as in attributing the stains to the individual. Similarly, the microbiome makeup of a soil sample may be utilised to establish geographic origin or to associate humans, animals, or things with a specific area, additionally microorganisms influence the decay process which may be used in depicting the Time Since death. Further in detecting the traces of the amount and concentration of alcohol, narcotics, and other forensically relevant compounds in human body or visceral tissues as they also affect the microbial community within human body. Beside these, there is much more scope of microbiomes to be explored in terms of forensic investigation, this review focuses on multidimensional approaches to human microbiomes from a forensic standpoint, implying the potential of microbiomes as an emerging tool for forensic investigations such as individual variability via skin microbiomes, reconstructing crime scene, and linking evidence to individual.

Cost Effective Method for gDNA Isolation from the Cecal Content and High Yield Procedure for RNA Isolation from the Colonic Tissue of Mice

Microbiome studies are quickly gaining momentum. Since most of the resident microbes (consisting of bacteria, fungi, and viruses) are difficult to culture, sequencing the microbial genome is the method of choice to characterize them. It is therefore important to have efficient methodology for gDNA isolation of gut microbes. Mouse models are widely used to understand human disease etiology while avoiding human ethics-related complications. However, the widely used kit-based methods are costly, and sometimes yields (in terms of quality and quantity) are sub-optimal. To overcome this problem, we developed a straightforward, standardized DNA isolation procedure from mouse cecal content for further microbiome-related studies. The reagents we used to standardize the procedure are readily available even in a not-so-well-equipped laboratory, and the reagents are not expensive. The yield and quality of the DNA are also better than those obtained by the readily available kit-based methods. Additionally, we modified the kit-based method of RNA isolation from the colon tissue sample of the mouse for better yield. Churning the tissue with liquid nitrogen at the beginning of the procedure improves RNA quality and quantity. Graphical abstract.

Aromatic-turmerone ameliorates DSS-induced ulcerative colitis via modulating gut microbiota in mice

Curcuma longa L. is one of the traditional Chinese herbs in the list of medicinal and food homology. Aromatic-turmerone is the main ingredient in turmeric essential oil. The aim of the present study is to investigate the treatment of Aromatic-turmerone on DSS-included colitis and its regulatory effect on intestinal flora disorder. Male KM mice supplemented with different concentration of aromatic-turmerone and mesalazine are subjected to 2% DSS in drinking water to induce colitis. Colon and cecum contents were collected for colitis lesion evaluation and inflammation-related gene analysis and colon contents for gut microbiota. The results show that treatments with Aromatic-turmerone significantly prevents colon shortening, alleviates the damage of colonic tissue, and reduces colonic inflammatory cytokines TNF-α and COX-2. Furthermore, the 16S rDNA gene sequence data indicate that Aromatic-turmerone improve the abundance of bacterial species, maintain some beneficial bacteria, and reduce harmful bacteria. Aromatic-turmerone downregulates the colonic inflammatory cytokines and modulates the abundance of intestinal flora, which is conductive to ameliorates DSS-induced colitis. Regularly intake of the edible herb may be help to prevent ulcerative colitis-related diseases.

Variability in the Pre-Analytical Stages Influences Microbiome Laboratory Analyses

Introduction: There are numerous confounding variables in the pre-analytical steps in the analysis of gut microbial composition that affect data consistency and reproducibility. This study compared two DNA extraction methods from the same faecal samples to analyse differences in microbial composition. Methods: DNA was extracted from 20 faecal samples using either (A) chemical/enzymatic heat lysis (lysis buffer, proteinase K, 95 °C + 70 °C) or (B) mechanical and chemical/enzymatic heat lysis (bead-beating, lysis buffer, proteinase K, 65 °C). Gut microbiota was mapped through the 16S rRNA gene (V3−V9) using a set of pre-selected DNA probes targeting >300 bacteria on different taxonomic levels. Apart from the pre-analytical DNA extraction technique, all other parameters including microbial analysis remained the same. Bacterial abundance and deviations in the microbiome were compared between the two methods. Results: Significant variation in bacterial abundance was seen between the different DNA extraction techniques, with a higher yield of species noted in the combined mechanical and heat lysis technique (B). The five predominant bacteria seen in both (A) and (B) were Bacteroidota spp. and Prevotella spp. (p = NS), followed by Bacillota (p = 0.005), Lachhnospiraceae (p = 0.0001), Veillonella spp. (p < 0.0001) and Clostridioides (p < 0.0001). Conclusion: As microbial testing becomes more easily and commercially accessible, a unified international consensus for optimal sampling and DNA isolation procedures must be implemented for robustness and reproducibility of the results.

The Oral, Gut Microbiota and Cardiometabolic Health of Indigenous Orang Asli Communities

The Orang Asli (OA) of Malaysia have been relatively understudied where little is known about their oral and gut microbiomes. As human health is closely intertwined with the human microbiome, this study first assessed the cardiometabolic health in four OA communities ranging from urban, rural to semi-nomadic hunter-gatherers. The urban Temuan suffered from poorer cardiometabolic health while rural OA communities were undergoing epidemiological transition. The oral microbiota of the OA were characterised by sequencing the V4 region of the 16S rRNA gene. The OA oral microbiota were unexpectedly homogenous, with comparably low alpha diversity across all four communities. The rural Jehai and Temiar PP oral microbiota were enriched for uncharacterised bacteria, exhibiting potential for discoveries. This finding also highlights the importance of including under-represented populations in large cohort studies. The Temuan oral microbiota were also elevated in opportunistic pathogens such as Corynebacterium, Prevotella, and Mogibacterium, suggesting possible oral dysbiosis in these urban settlers. The semi-nomadic Jehai gut microbiota had the highest alpha diversity, while urban Temuan exhibited the lowest. Rural OA gut microbiota were distinct from urban-like microbiota and were elevated in bacteria genera such as Prevotella 2, Prevotella 9, Lachnospiraceae ND3007, and Solobacterium. Urban Temuan microbiota were enriched in Odoribacter, Blautia, Parabacetroides, Bacteroides and Ruminococcacecae UCG-013. This study brings to light the current health trend of these indigenous people who have minimal access to healthcare and lays the groundwork for future, in-depth studies in these populations.

Differences in the gut microbiome composition of Korean children and adult samples based on different DNA isolation kits

Recent studies have revealed that the composition of human gut microbiota varies according to region, race, age, diet, living environment, and sampling and DNA extraction method. The purpose of this study was to broaden our understanding of the intestinal microbial composition of Koreans by conducting a 16S rRNA amplicon sequencing on 78 Korean samples composed of adults, children, normal and obese groups. We compared the microbiome composition and diversity of these groups at different levels including the phylum and genus level using two different stool DNA extraction kits of QIAamp® PowerFecal® DNA Kit (Qiagen, Hilden, Germany) and CT Max Fecal DNA Kit (Ct bio, Korea). We found that Ct bio (Ct) kit recovered higher DNA yields and OTUs than QIAamp® PowerFecal® DNA Kit (Qia). The Ct kit, which adopted more rigorous bead beating method, detected the most Gram-positive (G+) bacteria, Firmicutes, at the Phylum level, whereas the Qia kit, which used a less rigorous cell lysis method, found the most Gram-negative (G-) bacteria, Bacteroidetes. The Firmicutes-to-Bacteroidetes (F/B) ratio showed no significant difference between the obese and the normal groups of same kit; however, they were significantly different with two different kits. There was a difference in the intestinal flora between healthy Korean adults and children. The taxa that differed significantly between the adults and children were Bacteroides, Bifidobacterium, Prevotella, and Subdoligranulum. There was no significant difference in the intestinal flora between the normal weight group and the obese group in adults and children, respectively. This is probably because the difference in body mass index (BMI) between the sample groups collected in this study is statistically significant, but it is not large enough to show a clear difference in the flora. Therefore, these results should be interpreted with caution while considering the BMI values and Korean obesity criterion together.

The impacts of faecal subsampling on microbial compositional profiling

Objective

Despite the move to at-home, small-volume collection kits to facilitate large population-based studies of faecal microbial compositional profiling, there remains limited reporting on potential impacts of faecal subsampling approaches on compositional profiles. This study aimed to compare the microbial composition from faecal subsamples (< 5 g) collected from the beginning and end of a single bowel movement in ten otherwise healthy adults (6 female, 4 male; age: 24–55 years). Microbial composition was determined by V3–V4 16s rRNA sequencing and compared between subsamples.

Results

There were no significant differences in OTU count (p = 0.32) or Shannon diversity index (p = 0.29) between the subsamples. Comparison of relative abundance for identified taxa revealed very few differences between subsamples. At the lower levels of taxonomic classification differences in abundance of the Bacillales (p = 0.02) and the Eubacteriaceae family (p = 0.03), and the Eubacterium genera (p = 0.03) were noted. The observation of consistent microbial compositional profiles between faecal subsamples from the beginning and end of a single bowel movement is an important outcome for study designs employing this approach to faecal sample collection. These findings provide assurance that use of a faecal subsample for microbial composition profiling is generally representative of the gut luminal contents more broadly.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-05923-6.

A systematic review of gut microbiota composition in observational studies of major depressive disorder, bipolar disorder and schizophrenia

The emerging understanding of gut microbiota as 'metabolic machinery' influencing many aspects of physiology has gained substantial attention in the field of psychiatry. This is largely due to the many overlapping pathophysiological mechanisms associated with both the potential functionality of the gut microbiota and the biological mechanisms thought to be underpinning mental disorders. In this systematic review, we synthesised the current literature investigating differences in gut microbiota composition in people with the major psychiatric disorders, major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ), compared to 'healthy' controls. We also explored gut microbiota composition across disorders in an attempt to elucidate potential commonalities in the microbial signatures associated with these mental disorders. Following the PRISMA guidelines, databases were searched from inception through to December 2021. We identified 44 studies (including a total of 2510 psychiatric cases and 2407 controls) that met inclusion criteria, of which 24 investigated gut microbiota composition in MDD, seven investigated gut microbiota composition in BD, and 15 investigated gut microbiota composition in SZ. Our syntheses provide no strong evidence for a difference in the number or distribution (α-diversity) of bacteria in those with a mental disorder compared to controls. However, studies were relatively consistent in reporting differences in overall community composition (β-diversity) in people with and without mental disorders. Our syntheses also identified specific bacterial taxa commonly associated with mental disorders, including lower levels of bacterial genera that produce short-chain fatty acids (e.g. butyrate), higher levels of lactic acid-producing bacteria, and higher levels of bacteria associated with glutamate and GABA metabolism. We also observed substantial heterogeneity across studies with regards to methodologies and reporting. Further prospective and experimental research using new tools and robust guidelines hold promise for improving our understanding of the role of the gut microbiota in mental and brain health and the development of interventions based on modification of gut microbiota.

Centennial Review: Factors affecting the chicken gastrointestinal microbial composition and their association with gut health and productive performance

Maintenance of "gut health" is considered a priority in commercial chicken farms, although a precise definition of what constitutes gut health and how to evaluate it is still lacking. In research settings, monitoring of gut microbiota has gained great attention as shifts in microbial community composition have been associated with gut health and productive performance. However, microbial signatures associated with productivity remain elusive because of the high variability of the microbiota of individual birds resulting in multiple and sometimes contradictory profiles associated with poor or high performance. The high costs associated with the testing and the need for the terminal sampling of a large number of birds for the collection of gut contents also make this tool of limited use in commercial settings. This review highlights the existing literature on the chicken digestive system and associated microbiota; factors affecting the gut microbiota and emergence of the major chicken enteric diseases coccidiosis and necrotic enteritis; methods to evaluate gut health and their association with performance; main issues in investigating chicken microbial populations; and the relationship of microbial profiles and production outcomes. Emphasis is given to emerging noninvasive and easy-to-collect sampling methods that could be used to monitor gut health and microbiological changes in commercial flocks.

Integrating the human microbiome in the forensic toolkit: Current bottlenecks and future solutions

Over the last few years, advances in massively parallel sequencing technologies (also referred to next generation sequencing) and bioinformatics analysis tools have boosted our knowledge on the human microbiome. Such insights have brought new perspectives and possibilities to apply human microbiome analysis in many areas, particularly in medicine. In the forensic field, the use of microbial DNA obtained from human materials is still in its infancy but has been suggested as a potential alternative in situations when other human (non-microbial) approaches present limitations. More specifically, DNA analysis of a wide variety of microorganisms that live in and on the human body offers promises to answer various forensically relevant questions, such as post-mortem interval estimation, individual identification, and tissue/body fluid identification, among others. However, human microbiome analysis currently faces significant challenges that need to be considered and overcome via future forensically oriented human microbiome research to provide the necessary solutions. In this perspective article, we discuss the most relevant biological, technical and data-related issues and propose future solutions that will pave the way towards the integration of human microbiome analysis in the forensic toolkit.

Microbial taxa in dust and excreta associated with the productive performance of commercial meat chicken flocks

BACKGROUND

A major focus of research on the gut microbiota of poultry has been to define signatures of a healthy gut and identify microbiota components that correlate with feed conversion. However, there is a high variation in individual gut microbiota profiles and their association with performance. Population level samples such as dust and pooled excreta could be useful to investigate bacterial signatures associated with productivity at the flock-level. This study was designed to investigate the bacterial signatures of high and low-performing commercial meat chicken farms in dust and pooled excreta samples. Poultry house dust and fresh pooled excreta were collected at days 7, 14, 21, 28 and 35 of age from 8 farms of two Australian integrator companies and 389 samples assessed by 16S ribosomal RNA gene amplicon sequencing. The farms were ranked as low (n = 4) or high performers (n = 4) based on feed conversion rate corrected by body weight.

RESULTS

Permutational analysis of variance based on Bray-Curtis dissimilarities using abundance data for bacterial community structure results showed that company explained the highest variation in the bacterial community structure in excreta (R² = 0.21, p = 0.001) while age explained the highest variation in the bacterial community structure in dust (R² = 0.13, p = 0.001). Farm performance explained the least variation in the bacterial community structure in both dust (R² = 0.03, p = 0.001) and excreta (R² = 0.01, p = 0.001) samples. However, specific bacterial taxa were found to be associated with high and low performance in both dust and excreta. The bacteria taxa associated with high-performing farms in dust or excreta found in this study were Enterococcus and Candidatus Arthromitus whereas bacterial taxa associated with low-performing farms included Nocardia, Lapillococcus, Brachybacterium, Ruania, Dietzia, Brevibacterium, Jeotgalicoccus, Corynebacterium and Aerococcus.

CONCLUSIONS

Dust and excreta could be useful for investigating bacterial signatures associated with high and low performance in commercial poultry farms. Further studies on a larger number of farms are needed to determine if the bacterial signatures found in this study are reproducible.

Accurate quantification of bacterial abundance in metagenomic DNAs accounting for variable DNA integrity levels

The quantification of the total microbial content in metagenomic samples is critical for investigating the interplay between the microbiome and its host, as well as for assessing the accuracy and precision of the relative microbial composition which can be strongly biased in low microbial biomass samples. In the present study, we demonstrate that digital droplet PCR (ddPCR) can provide accurate quantification of the total copy number of the 16S rRNA gene, the gene usually exploited for assessing total bacterial abundance in metagenomic DNA samples. Notably, using DNA templates with different integrity levels, as measured by the DNA integrity number (DIN), we demonstrated that 16S rRNA copy number quantification is strongly affected by DNA quality and determined a precise correlation between quantification underestimation and DNA degradation levels. Therefore, we propose an input DNA mass correction, according to the observed DIN value, which could prevent inaccurate quantification of 16S copy number in degraded metagenomic DNAs. Our results highlight that a preliminary evaluation of the metagenomic DNA integrity should be considered before performing metagenomic analyses of different samples, both for the assessment of the reliability of observed differential abundances in different conditions and to obtain significant functional insights.

Technological tools and strategies for culturing human gut microbiota in engineered in vitro models

The gut microbiota directly impacts the pathophysiology of different human body districts. Consequently, microbiota investigation is an hot topic of research and its in vitro culture has gained extreme interest in different fields. However, the high sensitivity of microbiota to external stimuli, such as sampling procedure, and the physicochemical complexity of the gut environment make its in vitro culture a challenging task. New engineered microfluidic gut-on-a-chip devices have the potential to model some important features of the intestinal structure, but they are usually unable to sustain culture of microbiota over an extended period of time. The integration of gut-on-a-chip devices with bioreactors for continuous bacterial culture would lead to fast advances in the study of microbiota-host crosstalk. In this review, we summarize the main technologies for the continuous culture of microbiota as upstream systems to be coupled with microfluidic devices to study bacteria-host cells communication. The engineering of integrated microfluidic platforms, capable of sustaining both anaerobic and aerobic cultures, would be the starting point to unveil complex biological phenomena proper of the microbiota-host crosstalks, paving to way to multiple research and technological applications.

LAMP Assay for the Detection of Echinococcus multilocularis Eggs Isolated from Canine Faeces by a Cost-Effective NaOH-Based DNA Extraction Method

The detection of Echinococcus multilocularis in infected canids and the environment is pivotal for a better understanding of the epidemiology of alveolar echinococcosis in endemic areas. Necropsy/sedimentation and counting technique remain the gold standard for the detection of canid infection. PCR-based detection methods have shown high sensitivity and specificity, but they have been hardly used in large scale prevalence studies. Loop-mediated isothermal amplification (LAMP) is a fast and simple method to detect DNA with a high sensitivity and specificity, having the potential for field-application. A specific LAMP assay for the detection of E. multilocularis was developed targeting the mitochondrial nad1 gene. A crucial step for amplification-based detection methods is DNA extraction, usually achieved utilising silica-gel membrane spin columns from commercial kits which are expensive. We propose two cost-effective and straightforward methods for DNA extraction, using NaOH (method 1A) and InstaGene^TM Matrix (method 1B), from isolated eggs circumventing the need for commercial kits. The sensitivity of both assays with fox samples was similar (72.7%) with multiplex-PCR using protocol 1A and LAMP using protocol 1B. Sensitivity increased up to 100% when testing faeces from 12 foxes infected with more than 100 intestinal stages of E. multilocularis. For dogs, sensitivity was similar (95.4%) for LAMP and multiplex-PCR using protocol 1B and for both methods when DNA was extracted using protocol 1A (90.9%). The DNA extraction methods used here are fast, cheap, and do not require a DNA purification step, making them suitable for field studies in low-income countries for the prevalence study of E. multilocularis.

Toward Best Practice in Livestock Microbiota Research: A Comprehensive Comparison of Sample Storage and DNA Extraction Strategies

Understanding the roles of microorganisms in the animal gastrointestinal microenvironment is highly important for the development of effective strategies to manage and manipulate these microbial communities. In order to guide future animal gut microbiota research projects and standardization efforts, we have conducted a systematic comparison of 10 currently used sample preservation and DNA extraction approaches for pig and chicken microbiota samples and quantified their effects on bacterial DNA yield, quality, integrity, and on the resulting sequence-based bacterial composition estimates. The results showed how key stages of conducting a microbiota study, including the sample storage and DNA extraction, can substantially affect DNA recovery from the microbial community, and therefore, biological interpretation in a matrix-dependent manner. Our results highlight the fact that the influence of storage and extraction methods on the resulting microbial community structure differed by sample type, even within the same species. As the effects of these technical steps are potentially large compared with the real biological variability to be explained, standardization is crucial for accelerating progress in the area of livestock microbiota research. This study provided a framework to assist future animal gut microbiota research projects and standardization efforts.

Feral swine as sources of fecal contamination in recreational waters

Recreational waters are primary attractions at many national and state parks where feral swine populations are established, and thus are possible hotspots for visitor exposure to feral swine contaminants. Microbial source tracking (MST) was used to determine spatial and temporal patterns of fecal contamination in Congaree National Park (CONG) in South Carolina, U.S.A., which has an established population of feral swine and is a popular destination for water-based recreation. Water samples were collected between December 2017 and June 2019 from 18 surface water sites distributed throughout CONG. Host specific MST markers included human (HF183), swine (Pig2Bac), ruminant (Rum2Bac), cow (CowM3), chicken (CL), and a marker for shiga toxin producing Escherichia coli (STEC; stx2). Water samples were also screened for culturable Escherichia coli (E. coli) as part of a citizen science program. Neither the cow nor chicken MST markers were detected during the study. The human marker was predominantly detected at boundary sites or could be attributed to upstream sources. However, several detections within CONG without concurrent detections at upstream external sites suggested occasional internal contamination from humans. The swine marker was the most frequently detected of all MST markers, and was present at sites located both internal and external to the Park. Swine MST marker concentrations ≥ 43 gene copies/mL were associated with culturable E. coli concentrations greater than the U.S. Environmental Protection Agency beach action value for recreational waters. None of the MST markers showed a strong association with detection of the pathogenic marker (stx2). Limited information about the health risk from exposure to fecal contamination from non-human sources hampers interpretation of the human health implications.

Considerations for mosquito microbiome research from the Mosquito Microbiome Consortium

In the past decade, there has been increasing interest in mosquito microbiome research, leading to large amounts of data on different mosquito species, with various underlying physiological characteristics, and from diverse geographical locations. However, guidelines and standardized methods for conducting mosquito microbiome research are lacking. To streamline methods in mosquito microbiome research and optimize data quality, reproducibility, and comparability, as well as facilitate data curation in a centralized location, we are establishing the Mosquito Microbiome Consortium, a collaborative initiative for the advancement of mosquito microbiome research. Our overall goal is to collectively work on unraveling the role of the mosquito microbiome in mosquito biology, while critically evaluating its potential for mosquito-borne disease control. This perspective serves to introduce the consortium and invite broader participation. It highlights the issues we view as most pressing to the community and proposes guidelines for conducting mosquito microbiome research. We focus on four broad areas in this piece: (1) sampling/experimental design for field, semi-field, or laboratory studies; (2) metadata collection; (3) sample processing, sequencing, and use of appropriate controls; and (4) data handling and analysis. We finally summarize current challenges and highlight future directions in mosquito microbiome research. We hope that this piece will spark discussions around this area of disease vector biology, as well as encourage careful considerations in the design and implementation of mosquito microbiome research. Video Abstract.

On the Variability of Microbial Populations and Bacterial Metabolites within the Canine Stool. An in-Depth Analysis

Simple Summary

The present study investigated for the first time the impact that different sampling points have on the abundance of microbial populations and metabolites within the canine stool. We found that inner stool subsamples resulted in higher concentrations of bacterial metabolites but not of microbial populations. These findings suggest that stool subsampling is unlikely to represent the canine microbiota and metabolome uniformly. We believe that complete homogenisation of the whole stool prior to analysis may improve the final outcome when investigating the canine gut microbiome.

Abstract

Canine faecal microbial populations and metabolome are being increasingly studied to understand the interplay between host and gut microbiome. However, the distribution of bacterial taxa and microbial metabolites throughout the canine stool is understudied and currently no guidelines for the collection, storage and preparation of canine faecal samples have been proposed. Here, we assessed the effects that different sampling points have on the abundance of selected microbial populations and bacterial metabolites within the canine stool. Whole fresh faecal samples were obtained from five healthy adult dogs. Stool subsamples were collected from the surface to the inner part and from three equally sized areas (cranial, central, caudal) along the length axis of the stool log. All samples were finally homogenised and compared before and after homogenisation. Firmicutes, Bacteroidetes, Clostridium cluster I, Lactobacillus spp., Bifidobacterium spp. and Enterococcus spp. populations were analysed, as well as pH, ammonia and short-chain fatty acids (SCFA) concentrations. Compared to the surface of the stool, inner subsamples resulted in greater concentrations of SCFA and ammonia, and lower pH values. qPCR assay of microbial taxa did not show any differences between subsamples. Homogenisation of faeces does not affect the variability of microbial and metabolome data. Although the distribution patterns of bacterial populations and metabolites are still unclear, we found that stool subsampling yielded contradictory result and biases that can affect the final outcome when investigating the canine microbiome. Complete homogenisation of the whole stool is therefore recommended.

The effects of dairy and dairy derivatives on the gut microbiota: a systematic literature review

The effects of dairy and dairy-derived products on the human gut microbiota remains understudied. A systematic literature search was conducted using Medline, CINAHL, Embase, Scopus, and PubMed databases with the aim of collating evidence on the intakes of all types of dairy and their effects on the gut microbiota in adults. Risk of bias was assessed using the Cochrane risk-of-bias tool.The search resulted in 6,592 studies, of which eight randomized controlled trials (RCTs) met pre-determined eligibility criteria for inclusion, consisting of a total of 468 participants. Seven studies assessed the effect of type of dairy (milk, yogurt, and kefir) and dairy derivatives (whey and casein) on the gut microbiota, and one study assessed the effect of the quantity of dairy (high dairy vs low dairy). Three studies showed that dairy types consumed (milk, yogurt, and kefir) increased the abundance of beneficial genera Lactobacillus and Bifidobacterium. One study showed that yogurt reduced the abundance of Bacteroides fragilis, a pathogenic strain. Whey and casein isolates and the quantity of dairy consumed did not prompt changes to the gut microbiota composition. All but one study reported no changes to bacterial diversity in response to dairy interventions and one study reported reduction in bacterial diversity in response to milk intake.In conclusion, the results of this review suggest that dairy products such as milk, yogurt, and kefir may modulate the gut microbiota composition in favor to the host. However, the broader health implications of these findings remain unclear and warrant further studies.

The Dynamics of Interacting Bacterial and Fungal Communities of the Mouse Colon Following Antibiotics

We tested two hypotheses concerning the dynamics of intestinal microbial communities of young mice following antibiotic-induced disturbance. The first is that disturbance of the bacterial community causes disturbance of the fungal community. Our results were consistent with that hypothesis. Antibiotics significantly altered bacterial community structure. Antibiotics also altered fungal community structure, significantly increasing the relative abundance of Candida lusitaniae, a known pathogen, while simultaneously significantly decreasing the relative abundances of several other common fungal species. The result was a temporary decrease in fungal diversity. Moreover, bacterial load was negatively correlated with the relative abundances of Candida lusitaniae and Candida parapsilosis, while it was positively correlated with the relative abundances of many other fungal species. Our second hypothesis is that control mice serve as a source of probiotics capable of invading intestines of mice with disturbed microbial communities and restoring pre-antibiotic bacterial and fungal communities. However, we found that control mice did not restore disturbed microbial communities. Instead, mice with disturbed microbial communities induced disturbance in control mice, consistent with the hypothesis that antibiotic-induced disturbance represents an alternate stable state that is easier to achieve than to correct. Our results indicate the occurrence of significant interactions among intestinal bacteria and fungi and suggest that the stimulation of certain bacterial groups may potentially be useful in countering the dominance of fungal pathogens such as Candida spp. However, the stability of disturbed microbial communities could complicate recovery.

Learning machine approach reveals microbial signatures of diet and sex in dog

The characterization of the microbial population of many niches of the organism, as the gastrointestinal tract, is now possible thanks to the use of high-throughput DNA sequencing technique. Several studies in the companion animals field already investigated faecal microbiome in healthy or affected subjects, although the methodologies used in the different laboratories and the limited number of animals recruited in each experiment does not allow a straight comparison among published results. In the present study, we report data collected from several in house researches carried out in healthy dogs, with the aim to seek for a variability of microbial taxa in the faeces, caused by factors such as diet and sex. The database contains 340 samples from 132 dogs, collected serially during dietary intervention studies. The procedure of samples collection, storage, DNA extraction and sequencing, bioinformatic and statistical analysis followed a standardized pipeline. Microbial profiles of faecal samples have been analyzed applying dimensional reduction discriminant analysis followed by random forest analysis to the relative abundances of genera in the feces as variables. The results supported the responsiveness of microbiota at a genera taxonomic level to dietary factor and allowed to cluster dogs according this factor with high accuracy. Also sex factor clustered dogs, with castrated males and spayed females forming a separated group in comparison to intact dogs, strengthening the hypothesis of a bidirectional interaction between microbiota and endocrine status of the host. The findings of the present analysis are promising for a better comprehension of the mechanisms that regulate the connection of the microorganisms living the gastrointestinal tract with the diet and the host. This preliminary study deserves further investigation for the identification of the factors affecting faecal microbiome in dogs.

Thermus thermophilus DNA can be used as internal control for process monitoring of clinical metagenomic next-generation sequencing of urine samples

INTRODUCTION

Metagenomics is increasingly considered for clinical diagnostics. In order for this technology to become integrated in the clinical microbiology laboratory, process controls are required. Molecular diagnostic tests typically integrate an internal control (IC) to detect potential sources of variation and technical failure. However, few studies report on the integration of an IC in metagenomics.

AIM

We aimed to develop an easy-to-use IC method for the process control of library preparation and sequencing applied to metagenomics in clinical microbiology diagnostics using Thermus thermophilus DNA.

METHODOLOGY

DNA was extracted from urine samples and sequenced on the Ion Torrent Proton in the absence and presence of incremental concentrations (0.5-2-5%) of IC. Between aliquots of each sample, we compared the IC relative abundance (RA), and after in silico subtraction of IC reads, analysed microbial composition and the RA of pathogens. The optimal IC concentration was defined as the lowest concentration still detectable in all samples with the smallest impact on the microbial composition.

RESULTS

The RA of IC correlated linearly with the spiked IC concentration (r² = 0.99). IC added in a concentration of 0.5% of the total DNA concentration was detectable in all sample aliquots, regardless of human-bacterial DNA proportion, and after in silico removal gave the smallest difference in RA of pathogens compared to the sample aliquot sequenced in the absence of IC. The microbial composition in the presence and absence of IC was highly similar after in silico removal of IC reads (median BC-dissimilarity per sample: 0.059), provided samples had a mean of >10,000 bacterial reads.

CONCLUSION

T. thermophilus DNA at a percentage of 0.5% of the total DNA concentration was successfully applied for the process control of metagenomics of urine samples. We demonstrated negligible alterations in sample microbial composition after in silico subtraction of IC reads. This approach contributes toward implementation of metagenomics in the clinical microbiology laboratory.

Evaluation of fecal DNA extraction protocols for human gut microbiome studies

BACKGROUND

DNA extraction is an important factor influencing the microbiome profile in fecal samples. Considering that the QIAamp DNA Stool Mini Kit, one of the most commonly used DNA extraction kits, is no longer manufactured, this study aimed to investigate whether a new commercially available kit, the QIAamp PowerFecal Pro DNA Kit, yields comparable microbiome profiles with those previously obtained using the QIAamp DNA Stool Mini Kit.

RESULTS

We extracted DNA from fecal samples of 10 individuals using three protocols (protocol P of the QIAamp PowerFecal Pro DNA Kit, and protocols SB and S of the QIAamp DNA Stool Mini Kit with and without an additional bead-beating step, respectively) in triplicate. Ninety extracted DNA samples were subjected to 16S rRNA gene sequencing. DNA quality measured by 260/280 absorbance ratios was found to be optimal in protocol P. Additionally, the DNA quantity and microbiome diversity obtained using protocol P were significantly higher than those of protocol S, however, did not differ significantly from those of protocol SB. Based on the overall microbiome profiles, variations between protocol P and protocol SB or S were significantly less than between-individual variations. Furthermore, most genera were not differentially abundant in protocol P compared to the other protocols, and the number of differentially abundant genera, as well as the degree of fold-changes were smaller between protocols P and SB than between protocols P and S.

CONCLUSIONS

The QIAamp PowerFecal Pro DNA Kit exhibited microbiome analysis results that were comparable with those of the QIAamp DNA Stool Mini Kit with a bead-beating step. These results will prove useful for researchers investigating the gut microbiome in selecting an alternative protocol to the widely used but discontinued kit.

Extrinsic Factors Shaping the Skin Microbiome

Human skin, our most environmentally exposed organ, is colonized by a vast array of microorganisms constituting its microbiome. These bacterial communities are crucial for the fulfillment of human physiological functions such as immune system modulation and epidermal development and differentiation. The structure of the human skin microbiome is established during the early life stages, starting even before birth, and continues to be modulated throughout the entire life cycle, by multiple host-related and environmental factors. This review focuses on extrinsic factors, ranging from cosmetics to the environment and antibacterial agents, as forces that impact the human skin microbiome and well-being. Assessing the impact of these factors on the skin microbiome will help elucidate the forces that shape the microbial populations we coexist with. Furthermore, we will gain additional insight into their tendency to stimulate a healthy environment or to increase the propensity for skin disorder development.

Method Validation for Extraction of DNA from Human Stool Samples for Downstream Microbiome Analysis

Background: A formal method validation for biospecimen processing in the context of accreditation in laboratories and biobanks is lacking. A previously optimized stool processing protocol was validated for fitness-for-purpose for downstream microbiome analysis. Materials and Methods: DNA extraction from human stool was validated with various collection tubes, stabilizing solutions and storage conditions in terms of fitness-for-purpose for downstream microbiome analysis, robustness, and sample stability. Acceptance criteria were based on accurate identification of a reference material, homogeneity of extracted samples, and sample stability in a 2-year period. Results: The automated DNA extraction using the chemagic™ Magnetic Separation Module I (MSM I) extracted 8 out of 8 bacteria in the ZymoBIOMICS^® Microbial Community Standard. Seven tested stabilizing solutions (OMNIgene^®•GUT, RNAlater^®, AquaStool™, RNAssist, PerkinElmer SEB lysis buffer, and DNA Genotek's CP-150) were all compatible with the chemagic MSM I and showed no significant difference in microbiome alpha diversity and no significant difference in the overall microbiome composition compared to the baseline snap-frozen stool sample. None of the stabilizing solutions showed intensive polymerase chain reaction (PCR) inhibition in the SPUD assay. However, when we take into account more stringent criteria which include a higher double-stranded DNA yield, higher DNA purity, and absence of PCR inhibition, we recommend the use of OMNIgene•GUT, RNAlater, or AquaStool as alternatives to rapid freezing of samples. The highest sample homogeneity was achieved with RNAlater- and OMNIgene•GUT -stabilized samples. Sample stability after a 2-year storage in -80°C was seen with OMNIgene•GUT -stabilized samples. Conclusions: We validated a combination of a stool processing method with various collection methods, suitable for downstream microbiome applications. Sample collection, storage conditions and DNA extraction methods can influence the microbiome profile results. Laboratories and biobanks should ensure that these conditions are systematically recorded in the scope of accreditation.