Sources of gut microbiota variation in a large longitudinal Finnish infant cohort

Early life gut microbiome and its impact on childhood health and chronic conditions

The development of the gut microbiome is crucial to human health, particularly during the first three years of life. Given its role in immune development, disturbances in the establishment process of the gut microbiome may have long term consequences. This review summarizes evidence for these claims, highlighting compositional changes of the gut microbiome during this critical period of life as well as factors that affect gut microbiome development. Based on human and animal data, we conclude that the early-life microbiome is a determinant of long-term health, impacting physiological, metabolic, and immune processes. The early-life gut microbiome field faces challenges. Some of these challenges are technical, such as lack of standardized stool collection protocols, inconsistent DNA extraction methods, and outdated sequencing technologies. Other challenges are methodological: small sample sizes, lack of longitudinal studies, and poor control of confounding variables. To address these limitations, we advocate for more robust research methodologies to better understand the microbiome's role in health and disease. Improved methods will lead to more reliable microbiome studies and a deeper understanding of its impact on health outcomes.

Travel to the tropics: Impact on gut microbiota

BACKGROUND

Visitors to low- and middle-income countries (LMICs) encounter numerous new intestinal microbes, including diarrhoeal pathogens and multidrug-resistant (MDR) bacteria, such as extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE). Consequently, many develop travellers' diarrhoea (TD) and/or become colonised by ESBL-PE. We explored the impact of LMIC travel, TD, and ESBL-PE/diarrheal pathogen colonisation on gut microbiota.

METHODS

The present study included 92 participants from the clinical vaccine trial OEV123, who spent 12 days in Benin, West Africa, and provided exploratory pre- and post-travel stool microbiota samples. The samples were subjected to quantitative polymerase chain reaction (qPCR) to detect diarrhoeal pathogens and 16S rRNA gene amplicon sequencing for microbiota profiling.

RESULTS

Travel significantly altered gut microbiota, showing reduced richness, decreased α-diversity, and a 40-fold increase in Escherichia/Shigella. qPCR detected diarrhoeagenic Escherichia coli (DEC) in post-travel stools of 89 % of the 92 participants. No specific microbiota signatures were linked to TD or ESBL-PE acquisition. Participants acquiring multiple DEC pathotypes had higher pre-travel levels of Ruminococcaceae and Coprococcus spp., while their post-travel microbiota was enriched with oxygen-tolerant and oral and upper gastrointestinal tract-associated taxa.

CONCLUSION

Travel to an LMIC significantly impacted intestinal microbiota. Individuals with high pre-travel proportions of Ruminococcaceae and Coprococcus spp. acquired a greater DEC pathotype diversity. However, no specific pre-travel microbiota profile was identified as protective against or predisposing to TD or acquisition of MDR bacteria.

Dynamics of gut resistome and mobilome in early life: a meta-analysis

BACKGROUND

The gut microbiota of infants harbours a higher proportion of antibiotic resistance genes (ARGs) compared to adults, even in infants never exposed to antibiotics. Our study aims to elucidate this phenomenon by analysing how different perinatal factors influence the presence of ARGs, mobile genetic elements (MGEs), and their bacterial hosts in the infant gut.

METHODS

We searched MEDLINE and Embase up to April 3rd, 2023, for studies reporting infant cohorts with shotgun metagenomic sequencing of stool samples. The systematic search identified 14 longitudinal infant cohorts from 10 countries across three continents, featuring publicly available sequencing data with corresponding metadata. For subsequent integrative bioinformatic analyses, we used 3981 high-quality metagenomic samples from 1270 infants and 415 mothers.

FINDINGS

We identified distinct trajectories of the resistome and mobilome associated with birth mode, gestational age, antibiotic use, and geographical location. Geographical variation was exemplified by differences between cohorts from Europe, Southern Africa, and Northern America, which showed variation in both diversity and abundance of ARGs. On the other hand, we did not detect a significant impact of breastfeeding on the infants' gut resistome. More than half of detected ARGs co-localised with plasmids in key bacterial hosts, such as Escherichia coli and Enterococcus faecalis. These ARG-associated plasmids were gradually lost during infancy. We also demonstrate that E. coli role as a primary modulator of the infant gut resistome and mobilome is facilitated by its increased abundance and strain diversity compared to adults.

INTERPRETATION

Birth mode, gestational age, antibiotic exposure, and geographical location significantly influence the development of the infant gut resistome and mobilome. A reduction in E. coli relative abundance over time appears as a key factor driving the decrease in both resistome and plasmid relative abundance as infants grow.

FUNDING

Centre for Advanced Study in Oslo, Norway. Centre for New Antibacterial Strategies through the Tromsø Research Foundation, Norway.

Exploring the neurotoxic effects of microbial metabolites: A potential link between p-Cresol and autism spectrum disorders?

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a complex etiology, including genetic and environmental factors. A growing body of evidence (preclinical and clinical studies) implicates a potential role of gut microbiome dysregulation in ASD pathophysiology. This review focuses on the microbial metabolite p-Cresol, produced by certain gut bacteria such as Clostridium, and its potential role in ASD. The review summarizes studies investigating the gut microbiome composition in ASD patients, particularly the increased abundance of Clostridium species and associated gastrointestinal symptoms. The potential neurotoxic effects of p-Cresol are explored, including its influence on neurotransmitter metabolism (especially dopamine), neuroinflammation, and brain development. The mechanistic findings from the preclinical studies of p-Cresol's induction of ASD-like behaviors and its impact on the dopaminergic system are discussed. Literature studies indicated increased levels of p-Cresol in the urine of patients with ASD. This increasing evidence suggests that p-Cresol may serve as a crucial biomarker for understanding the relationship between gut microbiota and ASD, opening avenues for potential diagnostic and therapeutic interventions.

Fecal microbiota and genetics in pediatric-onset orofacial granulomatosis and Crohn´s disease

Orofacial granulomatosis (OFG) is a rare chronic inflammatory condition. It is under debate, whether it is a condition of its own or merely a subtype of Crohn's disease (CD). We aimed to search for markers characteristic of patients with pediatric-onset OFG compared to patients with pediatric-onset CD. We recruited young patients with OFG (with or without CD, n = 29), CD (n = 24), and healthy controls (n = 20). All participants provided a fecal sample for microbiota and calprotectin analyses and saliva for DNA analysis of genes associated with OFG and kept a 3-day food diary. Oral disease activity was evaluated using The Oral Disease Activity Score by an otorhinolaryngologist and a dentist. We observed decreased relative abundance in class Clostridia and increased relative abundances of classes Actinobacteria and Bacilli in the feces of patients with OFG when compared to patients with CD and healthy controls. The relative abundances of Bifidobacterium adolescentis increased and Faecalibacterium prausnitzii decreased along with the increase in the Oral Disease Activity Score. We found the NOD2 gene rs8057341 allele A to be enriched in patients with OFG compared to patients with CD. These findings support the theory that OFG is a distinct disease phenotype.

A novel robust network construction and analysis workflow for mining infant microbiota relationships

The gut microbiota plays a crucial role in infant health, with its development during the first 1,000 days influencing health outcomes. Understanding the relationships within the microbiota is essential to linking its maturation process to these outcomes. Several network-based methods have been developed to analyze the developing patterns of infant microbiota, but evaluating the reliability and effectiveness of these approaches remains a challenge. In this study, we created a test data pool using public infant microbiome data sets to assess the performance of four different network-based methods, employing repeated sampling strategies. We found that our proposed Probability-Based Co-Detection Model (PBCDM) demonstrated the best stability and robustness, particularly in network attributes such as node counts, average links per node, and the positive-to-negative link (P/N) ratios. Using the PBCDM, we constructed microbial co-existence networks for infants at various ages, identifying core genera networks through a novel network shearing method. Analysis revealed that core genera were more similar between adjacent age ranges, with increasing competitive relationships among microbiota as the infant microbiome matured. In conclusion, the PBCDM-based networks reflect known features of infant microbiota and offer a promising approach for investigating microbial relationships. This methodology could also be applied to future studies of genomic, metabolic, and proteomic data.

IMPORTANCE

As a research method and strategy, network analysis holds great potential for mining the relationships of bacteria. However, consistency and solid workflows to construct and evaluate the process of network analysis are lacking. Here, we provide a solid workflow to evaluate the performance of different microbial networks, and a novel probability-based co-existence network construction method used to decipher infant microbiota relationships. Besides, a network shearing strategy based on percolation theory is applied to find the core genera and connections in microbial networks at different age ranges. And the PBCDM method and the network shearing workflow hold potential for mining microbiota relationships, even possibly for the future deciphering of genome, metabolite, and protein data.

Fecal Microbiome and Metabolomic Profiles of Mixed-Fed Infants Are More Similar to Formula-Fed than Breastfed Infants

Many infants consume both human milk and infant formula (mixed-fed); however, few studies have investigated how mixed feeding affects the gut microbiome composition and metabolic profiles compared to exclusive breastfeeding or formula feeding. Herein, how delivery mode and early nutrition affect the microbiome and metabolome of 6-week-old infants in the STRONG Kids2 cohort was investigated. Fecal samples were collected from exclusively breastfed (BF; n = 25), formula-fed (FF; n = 25) or mixed-fed (MF; n = 25) participants. Within each feeding group, infants were either delivered vaginally (VD; n = 13) or by Cesarean section (CS; n = 12). Feeding mode affects the fecal microbiome diversity, composition, and functional potential, as well as metabolomic profiles regardless of delivery mode. Alpha and beta diversity of MF differed from that of BF (p < 0.05) but were comparable to FF infants. Functional analyses have shown 117 potential metabolic pathways differed between BF and FF, 112 between BF and MF, and 8 between MF and FF infants (p < 0.05, q < 0.10). Fecal metabolomic profiles of MF and FF clustered together and separated from BF infants. In total, 543 metabolites differed between BF and FF, 517 between BF and MF, and 3 between MF and FF (p < 0.05, q < 0.10). Delivery mode affected overall microbial composition (p = 0.022) at the genus level and 24 potential functional pathways, with 16 pathways being higher in VD than CS infants (p < 0.05, q < 0.10). Metabolomic analysis identified 47 differential metabolites between CS and VD, with 39 being lower in CS than VD (p < 0.05, q < 0.10). In summary, fecal microbiota composition and function and metabolite profiles of 6-week-old MF infants are closer to FF than BF infants.

The infant microbiota hopscotches between community states toward maturation-longitudinal stool parameters and microbiota development in a cohort of European toddlers

The development of the gut microbiome is critical during early life and is associated with infant health. To test whether this development is deterministic and how it is influenced by factors such as diet and mode of birth, we studied microbiota profiles and fecal parameters of 540 European infants, fed a synbiotic or control infant formula during their first year of life, up to 36 months of age. The diversity of the microbiota gradually increased until 36 months, at which point it resembled adult community states, indicating that microbiota maturation had occurred. However, distinct gut microbiota community states were observed that differed at each stage of maturation. The distribution of infants within the communities even at 36 months was significantly influenced by early life events, with a higher prevalence of infants born by cesarean section having the immature M36-C1 community state at 36 months. The microbial community state at one time point was not predictive of the next; instead, we observed hopscotching of the infant microbiota between different community states. This work provides new longitudinal data on the infant gut microbiome in relation to diet, suggesting that ecosystem development is not deterministic, but that early life events influence the community state of an individual's gut microbiota beyond infancy.

Associations between dietary fibers and gut microbiome composition in the EDIA longitudinal infant cohort

BACKGROUND

The infant gut microbiome undergoes rapid changes in the first year of life, supporting normal development and long-term health. Although diet shapes this process, the role of fibers in complementary foods on gut microbiome maturation is poorly understood.

OBJECTIVES

We explored how the transition from human milk to fibers in complementary foods shapes the taxonomic and functional maturation of the gut microbiome within the first year of life.

METHODS

We assessed the longitudinal and cross-sectional development of infant gut microbiomes (N = 68 infants) and metabolomes (N = 33 infants) using linear mixed models to uncover their associations to dietary fibers and their food sources. Fiber intakes were assessed with 3-d food records (months 3, 6, 9, and 12) relying on CODEX-compliant fiber fraction values, and questionnaires tracked the overall complementary food introduction. Bacterial species were identified and quantified via MetaPhlAn2 from metagenomic data, and metabolomic profiles were obtained using 4 LC-MS methods.

RESULTS

We identified 176 complementary food fiber-bacterial species associations. First plant-based fibers associated with microbiota compositions similar to breastfeeding, and further associated with aromatic amino acid-derived metabolites, including 5-hydroxyindoleacetic acid (total dietary fiber - complementary foods (g) - β = 3.50, CI: 2.48, 4.52, P = 6.53 × 10-5). Distinct fibers from different food categories showed unique associations with specific bacterial taxa. Key species, such as Faecalibacterium prausnitznii, associated with oat fibers (g/MJ, β = 2.18, confidence interval: 1.36, 2.84, P = 6.12 × 10-6), reflective of maturing microbial communities. Fiber intake during weaning associated with shifts in metabolite profiles, including immunomodulatory metabolites, with fiber effects observed in a source- and timing-dependent manner, implicated in gradual microbiome diversification.

CONCLUSIONS

Introducing complementary dietary fibers during the weaning period supports gut microbiome diversification and stabilization. Even minor dietary variations shows significant associations with microbial taxa and functions from the onset of weaning, highlighting the importance of infant dietary recommendations that support the gut microbiome maturation during early life. This trial was registered at clinicaltrials.gov as registration number NCT01735123.

Host-microbiota interactions in the infant gut revealed by daily faecal sample time series

Aim: This study aims to explore the interplay between host immune factors and gut microbiota in human infants in vivo using time-series daily stool samples and identify biomarkers of host-microbe interactions. Methods: 216 faecal samples collected from infants aged 5-6 or 11-12 months were analysed for gut microbiota composition, total bacterial load, and biomarkers of immune function. Results: We identified indications of microbial stimulation of eosinophil cationic protein (ECP), IgA, calprotectin (Cal), intestinal alkaline phosphatase (IAP), and Bactericidal/permeability-increasing protein (BPI) at 6 and 12 months, as well as stimulation of lipocalin 2 (LCN2), lactoferrin (LTF), and alpha-defensin-5 only at 6 months. The associations between biomarker concentrations and bacterial population growth were primarily positive at 6 months and mostly negative at 12 months, suggesting increasing host regulation of the microbiota with age. The exceptions were IAP, which was predictive of declining bacterial populations at both time points, and Cal, whose associations changed from negative at 6 months to positive at 12 months. Conclusion: There is an age-associated development in the correlation pattern between bacterial population growth and the biomarker concentrations, suggesting that host-microbe interactions change during early development. Albumin appeared as a potential marker of gut permeability, while LCN2 seemed to correlate with gut transit time. Mucin degradation appeared to decrease with age. Mucin2 and IAP emerged as potentially important regulators of the bacterial populations in the infant gut. The study demonstrates the utility of biomarker and bacteria profiling from daily stool samples for analysing in vivo associations between the immune system and the gut microbiota and provides evidence of host regulation of the microbiota in infants.

Changes in the intestinal microbiota of Japanese children during the first 3.5 years of life

Human gut microbiota plays a crucial role in health and disease. Infancy is a critical period for gut microbiota maturation and immune system development and has the potential to affect long-term health. Understanding the development of gut microbiota in Japanese children is essential because of regional differences and the long-term health effects of the early gut microbiota. However, while several longitudinal studies in Japan have explored the development of the gut microbiota after birth, more extended follow-up periods are still needed. In this study, we aimed to analyze the gut microbiota of 106 Japanese mother-child pairs from the Chiba Study of Mother and Child Health, Japan, over 3.5 years. The results showed that the alpha diversity of the gut microbiota in children increased with age, and its composition began to resemble that of adults. We identified four distinct clusters of gut microbiota that reflected different maturation stages. The similarity between the maternal and child gut microbiota appeared to follow a bimodal-like distribution, suggesting that the presence of older siblings may enhance this similarity. This study highlights the dynamic nature of gut microbiota development in Japanese children and deepens our understanding of the similarities between maternal and child gut microbiota.

The role of early life factors and green living environment in the development of gut microbiota in infancy: Population-based cohort study

OBJECTIVE

Early life microbial exposure influences the composition of gut microbiota. We investigated how early life factors, and the green living environment around infants' homes, influence the development of gut microbiota during infancy by utilizing data from the Steps to Healthy Development follow-up study (the STEPS study).

METHODS

The gut microbiota was analyzed at early (∼3 months, n = 959), and late infancy (∼13 months, n = 984) using 16S rRNA amplicon sequencing, and combined with residential green environment, measured as (1) Normalized Difference Vegetation Index, (2) Vegetation Cover Diversity, and (3) Naturalness Index within a 750 m radius. We compared gut microbiota diversity and composition between early and late infancy, identified significant individual and family level early life factors influencing gut microbiota, and determined the role of the residential green environment measures on gut microbiota development.

RESULTS

Alpha diversity (t-test, p < 0.001) and beta diversity (PERMANOVA, R2 = 0.095, p < 0.001) differed between early and late infancy. Birth mode was the strongest contributor to the gut microbiota community composition in early infancy (PERMANOVA, R2 = 0.005, p < 0.01) and the presence of siblings in late infancy (PERMANOVA, R2 = 0.007, p < 0.01). Residential green environment showed no association with community composition, whereas time spend outdoors did (PERMANOVA, R2 = 0.002, p < 0.05). Measures of greenness displayed a statistically significant association with alpha diversity during early infancy, not during late infancy (glm, p < 0.05). In adjusted analysis, the associations remained only with the Naturalness Index, where higher human impact on living environment was associated with decreased species richness (glm, Observed richness, p < 0.05).

CONCLUSIONS

The role of the residential green environment to the infant gut microbiota is especially important in early infancy, however, other early life factors, such as birth mode and presence of sibling, had a more significant effect on the overall community composition.

Gut microbiota wellbeing index predicts overall health in a cohort of 1000 infants

The human gut microbiota is central in regulating all facets of host physiology, and in early life it is thought to influence the host's immune system and metabolism, affecting long-term health. However, longitudinally monitored cohorts with parallel analysis of faecal samples and health data are scarce. In our observational study we describe the gut microbiota development in the first 2 years of life and create a gut microbiota wellbeing index based on the microbiota development and health data in a cohort of nearly 1000 infants using clustering and trajectory modelling. We show that infants' gut microbiota development is highly predictable, following one of five trajectories, dependent on infant exposures, and predictive of later health outcomes. We characterise the natural healthy gut microbiota trajectory and several different dysbiotic trajectories associated with different health outcomes. Bifidobacterium and Bacteroides appear as early keystone organisms, directing microbiota development and consistently predicting positive health outcomes. A microbiota wellbeing index, based on the healthy development trajectory, is predictive of general health over the first 5 years. The results indicate that gut microbiota succession is part of infant physiological development, predictable, and malleable. This information can be utilised to improve the predictions of individual health risks.

Bowel function in a prospective cohort of 1052 healthy term infants up to 4 months of age

The purpose of this study is to describe the defecation pattern of healthy infants up to 17 weeks of age. We included 1052 healthy term infants from the prospective HELMi cohort (NCT03996304). Parents filled in recurring online questionnaires on feeding, gastrointestinal function, and crying weekly for the first 17 weeks of life. Defecation frequency was highest at the age of 3 weeks (a median of 4 times/day, interquartile range (IQR) 2.9-5). At each time point, the median defecation frequency of breastfed infants was higher than that of infants receiving formula (e.g., at week 17 a median of 2 times/day, IQR 0.9-3.6, and a median of 1.1, IQR 0.6-1.4, respectively). The dominant color of the stool was most often yellow or light brown. Nearly black stools were reported in the first week of life in 3.4%. Nearly half (47.4%) of the infants had green stool color dominating for at least 1 week, with comparable frequency among breastfed (47.7%) and formula-fed (45.2%) infants. Green stools were associated with a higher defecation frequency (linear mixed-effect model p < 0.0001). Occasional blood in stool was reported in 9.3% and recurrent blood in 5.2% of the infants with no difference in stool consistency. Hard stools were rare (≤ 1%).     Conclusion: This study enlightens the spectrum of defecation patterns in healthy term infants during the first 17 weeks of life. A better understanding of bowel function helps healthcare professionals distinguish normal from abnormal when addressing defecation, the color of stools, and the type of feeding. What is Known: • Breastfed infants have more frequent and more yellow-colored stools than formula-fed infants. • Stools with green color are often suggested by the parents or even by medical professionals to indicate disease or discomfort in early life. What is New: • Nearly half of the healthy term infants had green stool dominating for at least one week during the first 17 weeks and occasional blood was reported in almost 10% of the infants during this period. • Data on normal variation in bowel function and stool may serve primary health care professionals when educating the families and caretakers of infants.

The dual role of 20(S)-protopanaxadiol in alleviating pulmonary fibrosis through the gut-lung axis

BACKGROUND

Pulmonary Fibrosis (PF) is a progressive lung disease characterized by the diffuse interstitial tissue, leading to severe breathing difficulties. The existing treatment methods are primarily aimed at slowing the progression of the disease, underscoring the urgent need to discover new drug interventions targeting novel sites. The "gut-lung axis" represents a complex bidirectional communication system where the gut microbiota not only influences lung immunity but also responds to lung-derived signals. Recent advances have uncovered that alterations in gut microbiota composition can significantly impact respiratory diseases, offering new insights into their pathogenesis and potential therapeutic approaches.

METHODS

This study is based on the fundamental concepts of the lung-gut axis and our previous research, further exploring the potential mechanisms of 20(S)-Protopanaxadiol (PPD) in ginseng against PF. We utilized a bleomycin-induced mouse model of PF and employed metabolomics and 16S rRNA sequencing to investigate the pathways through which PPD regulates the pulmonary fibrosis process via the gut-lung axis. Finally, we employed strategies such as antibiotic-induced microbiota disruption and fecal microbiota transplantation (FMT) to provide a comprehensive perspective on how PPD regulates pulmonary fibrosis through gut microbiota.

RESULTS

The results of the bleomycin (BLM) mouse model of PF proved that PPD can directly act on the glycolysis- related metabolic reprogramming process in lung and the AMPK/STING pathway to improve PF. Combined the analysis of gut microbiota and related metabolites, we found that PPD can regulate the process of PF through the gut-lung axis target points G6PD and SPHK1. FMT and antibiotic-induced microbiota disruption further confirmed intermediate effect of gut microbiota in PF process and the treatment of PPD. Our study suggests that PPD can alleviate the process of pulmonary fibrosis either by directly acting on the lungs or by regulating the gut microbiota.

CONCLUSION

This study positions PPD as a vanguard in the therapeutic landscape for pulmonary fibrosis, offering a dual mechanism of action that encompasses both modulation of gut microbiota and direct intervention at molecular targets. These insights highlight the immense therapeutic potential of harnessing the gut-lung axis.

Human milk oligosaccharide composition is affected by season and parity and associates with infant gut microbiota in a birth mode dependent manner in a Finnish birth cohort

BACKGROUND

Human milk oligosaccharides (HMOs), their determinants, infant gut microbiota and health are under extensive research; however, seldom jointly addressed. Leveraging data from the HELMi birth cohort, we investigated them collectively, considering maternal and infant secretor status.

METHODS

HMO composition in breastmilk collected 3 months postpartum (n = 350 mothers) was profiled using high-performance liquid chromatography. Infant gut microbiota taxonomic and functional development was studied at 3, 6, and 12 months (n = 823 stool samples) via shotgun metagenomic sequencing, focusing on HMO metabolism via glycoside hydrolase (GH) analysis. Maternal and infant secretor statuses were identified through phenotyping and genotyping, respectively. Child health, emphasizing allergies and antibiotics as proxies for infectious diseases, was recorded until 2 years.

FINDINGS

Mother's parity, irritable bowel syndrome, gestational diabetes, and season of milk collection associated with HMO composition. Neither maternal nor infant secretor status associated with infant gut microbiota, except for a few taxa linked to individual HMOs. Analysis stratified for birth mode revealed distinct patterns between the infant gut microbiota and HMOs. Child health parameters were not associated to infant or maternal secretor status.

INTERPRETATION

This comprehensive exploration unveils intricate links between secretor genotype, maternal factors, HMO composition, infant microbiota, and child health. Understanding these nuanced relationships is paramount for refining strategies to optimize early life nutrition and its enduring impact on long-term health.

FUNDING

Sweet Crosstalk EU H2020 MSCA ITN, Academy of Finland, Mary and Georg C. Ehrnrooth Foundation, Päivikki and Sakari Sohlberg Foundation, and Tekes.

A cohort study in family triads: impact of gut microbiota composition and early life exposures on intestinal resistome during the first two years of life

Antibiotic resistance genes (ARGs) are prevalent in the infant gut microbiota and make up the intestinal resistome, representing a community ARG reservoir. This study focuses on the dynamics and persistence of ARGs in the early gut microbiota, and the effect of early exposures therein. We leveraged 2,328 stool metagenomes from 475 children in the HELMi cohort and the available parental samples to study the diversity, dynamics, and intra-familial sharing of the resistome during the first two years of life. We found higher within-family similarity of the gut resistome composition and ARG load in infant-mother pairs, and between spouses, but not in father-infant pairs. Early gut microbiota composition and development correlated with the ARG load; Bacteroides correlated positively and Bifidobacterium negatively with the load, reflecting the typical resistance levels in these taxa. Caesarean delivered infants harbored lower ARG loads, partly reflecting the scarcity of Bacteroides compared to vaginally delivered. Exposure to intrapartum or post-natal antibiotics showed only modest associations with the ARG load and composition, mainly before 12 months. Our results indicate that the resistome is strongly driven by the normal development of the microbiota in early life, and suggest importance of longer evolution of ARGs over effects of recent antibiotic exposure.

The Role of Bifidobacterium in Liver Diseases: A Systematic Review of Next-Generation Sequencing Studies

The physiopathology of liver diseases is complex and can be caused by various factors. Bifidobacterium is a bacterial genus commonly found in the human gut microbiome and has been shown to influence the development of different stages of liver diseases significantly. This study investigated the relationship between the Bifidobacterium genus and liver injury. In this work, we performed a systematic review in major databases using the key terms "Bifidobacterium", "ALD", "NAFLD", "NASH", "cirrhosis", and "HCC" to achieve our purpose. In total, 31 articles were selected for analysis. In particular, we focused on studies that used next-generation sequencing (NGS) technologies. The studies focused on assessing Bifidobacterium levels in the diseases and interventional aimed at examining the therapeutic potential of Bifidobacterium in the mentioned conditions. Overall, the abundance of Bifidobacterium was reduced in hepatic pathologies. Low levels of Bifidobacterium were associated with harmful biochemical and physiological parameters, as well as an adverse clinical outcome. However, interventional studies using different drugs and treatments were able to increase the abundance of the genus and improve clinical outcomes. These results strongly support the hypothesis that changes in the abundance of Bifidobacterium significantly influence both the pathophysiology of hepatic diseases and the related clinical outcomes. In addition, our critical assessment of the NGS methods and related statistical analyses employed in each study highlights concerns with the methods used to define the differential abundance of Bifidobacterium, including potential biases and the omission of relevant information.