Exclusive breast-feeding, the early-life microbiome and immune response, and common childhood respiratory illnesses

Breastfeeding and risk of food allergy and allergic rhinitis in offspring: a systematic review and meta-analysis of cohort studies

The association between breastfeeding and the occurrence of allergic rhinitis (AR) and food allergy (FA) in offspring remains inconclusive. This review aims to comprehensively explore the potential relationships between various patterns and durations of breastfeeding and allergic diseases in offspring. We systematically searched PubMed, EMBASE, Cochrane, WOS databases, and Google Scholar for observational studies published up to March 30, 2023, that investigated the link between breastfeeding and allergies in offspring. The quality of the studies was assessed using the Newcastle-Ottawa Scale (NOS) and Joanna Briggs Institute (JBI). Pooled odds ratios (OR) and 95% confidence intervals (95% CI) were calculated employing an appropriate model based on the degree of heterogeneity. A total of 68 studies, encompassing 772,142 children, were ultimately included. The findings indicated that breastfeeding for more than 6 months was associated with a reduced risk of AR (OR = 0.88, 95% CI: 0.79 to 0.98) but posed a risk for FA (OR = 1.69, 95% CI: 1.27 to 2.25). Exclusive breastfeeding exhibited a protective effect against AR (OR = 0.94, 95% CI: 0.90 to 0.97), whereas non-breastfeeding was identified as a risk factor for AR (OR = 1.48; 95% CI: 1.03 to 2.12). No significant association was observed between breastfeeding patterns and FA.

CONCLUSION

Breastfeeding for more than 6 months proves to be an effective preventive measure against AR. However, large prospective high-quality studies are needed to investigate the potential risk of FA in children with prolonged breastfeeding.

WHAT IS KNOWN

• The impact of breastfeeding on allergic rhinitis and food allergy in offspring is controversial. • Previous meta-analyses fail to prove the effect of breastfeeding on food allergy in offspring of all ages.

WHAT IS NEW

• Breastfeeding for more than 6 months proves to be an effective preventive measure against AR. However, it potentially elevates the risk of FA in children. Non-breastfeeding is linked to an increased risk of AR in children, but there is no evidence of an association between breastfeeding patterns and FA in children. • The impact of breastfeeding on allergic rhinitis and food allergy in offspring may vary with the time and pattern of breastfeeding.

Melatonin restores DNFB-induced dysbiosis of skin microbiota in a mouse model of atopic dermatitis

BACKGROUND

The epidermic microbiota plays crucial roles in the pathogenesis of atopic dermatitis (AD), a common inflammatory skin disease. Melatonin (MLT) has been shown to ameliorate skin damage in AD patients, yet the underlying mechanism is unclear.

METHODS

Using 2,4-dinitrofluorobenzene (DNFB) to induce an AD model, MLT intervention was applied for 14 days to observe its pharmaceutical effect. Skin lesions were observed using HE staining, toluidine blue staining and electron microscopy. Dermal proinflammatory factor (IL-4 and IL-13) and intestinal barrier indices (ZO1 and Occludin) were assessed by immunohistochemistry and RT-qPCR, respectively. The dysbiotic microbiota was analyzed using 16S rRNA sequencing.

RESULTS

MLT significantly improved skin lesion size; inflammatory status (mast cells, IgE, IL-4, and IL-13); and the imbalance of the epidermal microbiota in AD mice. Notably, Staphylococcus aureus is the key bacterium associated with dysbiosis of the epidermal microbiota and may be involved in the fine modulation of mast cells, IL-4, IL-13 and IgE. Correlation analysis between AD and the gut revealed that intestinal dysbiosis occurred earlier than that of the pathological structure in the gut.

CONCLUSION

Melatonin reverses DNFB-induced skin damage and epidermal dysbiosis, especially in S. aureus.

Impact of Breastfeeding Duration on Adenoid Hypertrophy, Snoring and Acute Otitis Media: A Case-Control Study in Preschool Children

BACKGROUND

The aim of this study was to analyze the relationship between breastfeeding duration and adenoid size, snoring and acute otitis media (AOM).

METHODS

We analyzed the medical history of children admitted to the ENT outpatient clinic in 2022 and 2023, reported symptoms, ear, nose and throat (ENT) examination, and flexible nasopharyngoscopy examination of 145 children aged 3-5 years.

RESULTS

Breastfeeding duration of 3 and 6 months or more had a significant effect on the reduction of snoring (p = 0.021; p = 0.039). However, it had no effect on the adenoid size, mucus coverage and sleeping with an open mouth. Snoring was correlated with open mouth sleeping (p < 0.001), adenoid size with a 75% A/C ratio or more (p < 0.001), and adenoid mucus coverage in the Mucus of Adenoid Scale by Nasopharyngoscopy Assessment-MASNA scale (p = 0.009). Children who were breastfed for less than 3 months had more than a four-fold greater risk of snoring. There was a statistically significant correlation between AOM and gender (p = 0.033), breastfeeding duration in groups fed 1, 3 or 6 months or more (p = 0.018; p = 0.004; p = 0.004) and those fed with mother's breast milk 3 or 6 months or more (p = 0.009; p = 0.010). Moreover, a correlation was found between adenoid size and mucus coverage, tympanogram, and open-mouth sleeping (p < 0.001). Independent factors of snoring in 3- to 5-year-old children were breastfeeding duration of less than 3 months (p = 0.032), adenoid size with an A/C ratio of 75% or more (p = 0.023) and open mouth sleeping (p = 0.001).

CONCLUSIONS

Children breastfed for 3 and 6 months or more exhibited reduced rates of snoring. There was no effect of breastfeeding duration on adenoid size in children aged 3 to 5 years, suggesting that the link between breastfeeding duration and snoring is primarily associated with craniofacial development and muscle tone stimulation. A breastfeeding duration of 1 month or more plays a key role in reducing the rate of AOM. The mother's milk plays a protective role against AOM. The presence of mucus might be responsible for snoring in preschool children. A medical history of breastfeeding should be taken into consideration when snoring children are suspected of adenoid hypertrophy.

Association of rhinovirus and potentially pathogenic bacterial detections in the first 3 months of life with subsequent wheezing in childhood

OBJECTIVE

Airway interactions between viruses, especially rhinoviruses, and potentially pathogenic bacteria (PPB; Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis) in early infancy may increase the risk of subsequent wheezing and asthma. We evaluated the association between rhinovirus and PPB in the first 3 months of life and wheezing episodes before age 2 years and asthma at age 5-7 years.

METHODS

An Australian community-based birth cohort of healthy children involved parents collecting nasal swabs weekly and completing symptom diaries daily until age 2 years. In a follow-up subset, asthma diagnosis was assessed annually until age 7 years. Swabs were analyzed by real-time polymerase chain reaction assays. Children were included if they returned symptom diaries beyond age 3 months (wheeze) or were reviewed at age 5-7 years (asthma).

RESULTS

1440 swabs were returned by 146 children in the first 3 months of life. Wheeze and asthma outcomes were recorded for 146 and 84 children, respectively. Each additional week of rhinovirus detection increased the incidence of wheezing before age 2 years by 1.16 times (95% confidence interval [CI]: 0.99-1.35). There were no significant associations between bacteria and wheeze. Each additional week with H. influenzae increased the odds of asthma at age 5-7 years by 135% (odds ratio: 2.35, 95% CI: 0.99-5.58). No significant interaction was observed between rhinovirus and PPB for wheezing or asthma.

CONCLUSION

Early life rhinovirus infection was associated with wheezing before age 2 years and H. influenzae with asthma by age 5-7 years. Microbes may play an etiologic role in wheezing and asthma, warranting further study.

Asthma and Other Respiratory Diseases of Children in Relation to Personal Behavior, Household, Parental and Environmental Factors in West China

Asthma and other respiratory diseases, which are of great concern in public health, are paid less attention in areas that are less economically developed. This research aimed to study the prevalence of critical respiratory diseases of children living in West China and figure out the potential influencing factors. A total of 575 children under the age of 14 were recruited from Xinjiang, China, to participate in the study in 2022. Information on activity patterns, socioeconomic and parental factors, and household and surrounding environment situations was obtained using a questionnaire survey. Logistic regression models were applied to estimate the odds ratios of respiratory disease prevalence in relation to behavior patterns, household, parental and environmental factors, respectively. The prevalence of ever doctor-diagnosed asthma, doctor-diagnosed bronchitis and current bronchitis were 4.7%, 19.0% and 14.4%, respectively. The prevalence of doctor-diagnosed pneumonia was 8.2%, which was two times higher in urban than rural areas. Longer annual heating duration was significantly associated with higher risks in children's asthma and bronchitis, with an odds ratio (OR) and 95% confidence interval (95% CI) of 3.363 (95% CI: 1.215-9.298) and 1.267 (95% CI: 1.002-1.601), respectively. Opening the window longer in autumn would lead to higher risks of bronchitis, with ORs of 1.165 and 1.133, respectively, for doctor-diagnosed bronchitis and current bronchitis. Residential air pollution and having a residence close to waste incineration plant or garbage station were, respectively, significantly associated with higher risks of doctor-diagnosed bronchitis and asthma. Parental disease history was associated with a higher prevalence of children's asthma and respiratory diseases, whereas breastfeeding and doing physical exercise were, respectively, significantly associated with a lower risk of asthma. A high prevalence of respiratory diseases in children in West China may be partly attributed to longer annual heating time, opening windows longer in autumn, surrounding environmental pollution, as well as parental disease history, whereas promoting physical activity and breastfeeding could be an effective measure to reduce the risk of childhood asthma in West China.

Early-immune development in asthma: A review of the literature

This review presents a comprehensive examination of the various factors contributing to the immunopathogenesis of asthma from the prenatal to preschool period. We focus on the contributions of genetic and environmental components as well as the role of the nasal and gut microbiome on immune development. Predisposing genetic factors, including inherited genes associated with increased susceptibility to asthma, are discussed alongside environmental factors such as respiratory viruses and pollutant exposure, which can trigger or exacerbate asthma symptoms. Furthermore, the intricate interplay between the nasal and gut microbiome and the immune system is explored, emphasizing their influence on allergic immune development and response to environmental stimuli. This body of literature underscores the necessity of a comprehensive approach to comprehend and manage asthma, as it emphasizes the interactions of multiple factors in immune development and disease progression.

Infants exposed in utero to Hurricane Maria have gut microbiomes with reduced diversity and altered metabolic capacity

The gut microbiome is a potentially important mechanism that links prenatal disaster exposures with increased disease risks. However, whether prenatal disaster exposures are associated with alterations in the infant's gut microbiome remains unknown. We established a birth cohort study named Hurricane as the Origin of Later Alterations in Microbiome (HOLA) after Hurricane Maria struck Puerto Rico in 2017. We enrolled vaginally born Latino term infants aged 2 to 6 months, including n = 29 infants who were exposed in utero to Hurricane Maria in Puerto Rico and n = 34 infants who were conceived at least 5 months after the hurricane as controls. Shotgun metagenomic sequencing was performed on infant stool swabs. Infants exposed in utero to Hurricane Maria had a reduced diversity in their gut microbiome compared to the control infants, which was mainly seen in the exclusively formula-fed group (P = 0.02). Four bacterial species, including Bacteroides vulgatus, Clostridium innocuum, Bifidobacterium pseudocatenulatum, and Clostridium neonatale, were depleted in the exposure group compared to the control group. Compositional differences in the microbial community and metabolic genes between the exposure and control groups were significant, which were driven by the formula feeding group (P = 0.02 for the microbial community and P = 0.008 for the metabolic genes). Metabolic modules involved in carbohydrate metabolism were reduced in the exposure group. Prenatal maternal exposure to Hurricane Maria was associated with a reduced gut commensal and an altered microbial composition and metabolic potential in the offspring's gut. Breastfeeding can adjust the composition of the gut microbiomes of exposed infants. IMPORTANCE Climate change is a serious issue that is affecting human health. With more frequent and intense weather disasters due to climate change, there is an urgent need to evaluate and understand the impacts of prenatal disaster exposures on the offspring. The prenatal stage is a particularly vulnerable stage for disease origination. However, the impact of prenatal weather disaster exposures on the offspring's gut microbiome has not been evaluated. Our HOLA study starts to fill this knowledge gap and provides novel insights into the microbiome as a mechanism that links prenatal disaster exposures with elevated disease risks. Our major finding that reduced microbial diversity and altered metabolic capacity are associated with prenatal hurricane exposures warrants further studies to evaluate the impact of weather disasters on the unborn.

Importance of human milk for infants in the clinical setting: Updates and mechanistic links

INTRODUCTION

Human milk (HM) is the optimal source of nutrition for infants and has been implicated in multiple aspects of infant health. Although much of the existing literature has focused on the individual components that drive its nutrition content, examining HM as a biological system is needed for meaningful advancement of the field. Investigation of the nonnutritive bioactive components of HM and the maternal, infant, and environmental factors which affect these bioactives is important to better understand the importance of HM provision to infants. This information may inform care of clinical populations or infants who are critically ill, hospitalized, or who have chronic diseases and may benefit most from receiving HM.

METHODS

In this narrative review, we reviewed literature examining maternal and infant influences on HM composition with a focus on studies published in the last 10 years that were applicable to clinical populations.

RESULTS

We found multiple studies examining HM components implicated in infant immune and gut health and neurodevelopment. Additional work is needed to understand how donor milk and formula may be used in situations of inadequate maternal HM. Furthermore, a better understanding of how maternal factors such as maternal genetics and metabolic health influence milk composition is needed.

CONCLUSION

In this review, we affirm the importance of HM for all infants, especially clinical populations. An understanding of how HM composition is modulated by maternal and environmental factors is important to progress the field forward with respect to mechanistic links between HM biology and infant health outcomes.

Host microbiome-pathogen interactions in pediatric infections

PURPOSE OF REVIEW

In this review, we discuss recent research that has furthered our understanding of microbiome development during childhood, the role of the microbiome in infections during this life stage, and emerging opportunities for microbiome-based therapies for infection prevention or treatment in children.

RECENT FINDINGS

The microbiome is highly dynamic during childhood and shaped by a variety of host and environmental factors. In turn, the microbiome influences risk and severity of a broad range of infections during childhood, with recent studies highlighting potential roles in respiratory, gastrointestinal, and systemic infections. The microbiome exerts this influence through both direct interactions with potential pathogens and indirectly through modulation of host immune responses. The elucidation of some of these mechanisms by recent studies and the development of effective microbiome-based therapies for adults with recurrent Clostridioides difficile infection highlight the enormous promise that targeting the microbiome has for reducing the burden of infectious diseases during childhood.

SUMMARY

The microbiome has emerged as a key modifier of infection susceptibility and severity among children. Further research is needed to define the roles of microbes other than bacteria and to elucidate the mechanisms underlying microbiome-host and microbiome-pathogen interactions of importance to infectious diseases in children.

From gut to skin: exploring the potential of natural products targeting microorganisms for atopic dermatitis treatment

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease. Recent studies have revealed that interactions between pathogenic microorganisms, which have a tendency to parasitize the skin of AD patients, play a significant role in the progression of the disease. Furthermore, specific species of commensal bacteria in the human intestinal tract can have a profound impact on the immune system by promoting inflammation and pruritogenesis in AD, while also regulating adaptive immunity. Natural products (NPs) have emerged as promising agents for the treatment of various diseases. Consequently, there is growing interest in utilizing natural products as a novel therapeutic approach for managing AD, with a focus on modulating both skin and gut microbiota. In this review, we discuss the mechanisms and interplay between the skin and gut microbiota in relation to AD. Additionally, we provide a comprehensive overview of recent clinical and fundamental research on NPs targeting the skin and gut microbiota for AD treatment. We anticipate that our work will contribute to the future development of NPs and facilitate research on microbial mechanisms, based on the efficacy of NPs in treating AD.

Breast Milk Conferred Immunity to Infants Against COVID-19

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has notably impacted healthcare systems and everyday life worldwide. Regulatory authorities have approved the emergency use of SARS-CoV-2 vaccines due to the rapid spread of the virus. However, during vaccination testing, pregnant and breastfeeding women were initially excluded, leading to a lack of evidence-based recommendations. When taking the COVID-19 pandemic into account, breastfeeding has emerged as a potential defense mechanism against this infection due to its numerous benefits for newborns. Human breast milk contains immunoglobulins (IgA, IgG, and IgM), lactoferrin, and various cells that play an inevitable role in the newborn's protection against respiratory infections and immune system development. Various studies have highlighted that the onset and severity of respiratory infections in infants can be reduced through breastfeeding, and the effects are noticeable during the first six months of life and that breast milk also has the potential to enhance mucosal immunity and promote a diverse microbiome, reducing the risk of asthma, allergies, and enteric diseases through the provision of specific antibodies and immunological factors. Researchers have indicated that breastfeeding mothers who contracted and recovered from COVID-19 or received vaccination passed protective antibodies to their infants through breast milk. Although rare cases of detection of SARS-CoV-2 RNA in breast milk have been reported, the virus has not been cultured from these samples, suggesting a low risk of transmission to the breastfed baby. However, further research is essential to understand the extent of protection provided by breast milk against COVID-19 and the potential effect of distinct phases of lactation. Nonetheless, the current evidence supports the benefits and safety of breastfeeding during the pandemic. With appropriate safety measures, promoting breastfeeding can contribute to the overall health and well-being of infants during the phase of COVID-19.

The Role of the Microbiome in the Pathogenesis and Treatment of Asthma

The role of the microbiome in the pathogenesis and treatment of asthma is significant. The purpose of this article is to show the interplay between asthma and the microbiome, and main areas that require further research are also highlighted. The literature search was conducted using the PubMed database. After a screening process of studies published before May 2023, a total of 128 articles were selected in our paper. The pre-treatment bronchial microbiome in asthmatic patients plays a role in their responsiveness to treatment. Gut microbiota and its dysbiosis can contribute to immune system modulation and the development of asthma. The association between the microbiome and asthma is complex. Further research is necessary to clarify which factors might moderate that relationship. An appropriate gut microbiome and its intestinal metabolites are a protective factor for asthma development. Prebiotics and certain dietary strategies may have a prophylactic or therapeutic effect, but more research is needed to establish final conclusions. Although the evidence regarding probiotics is ambiguous, and most meta-analyses do not support the use of probiotic intake to reduce asthma, several of the most recent studies have provided promising effects. Further studies should focus on the investigation of specific strains and the examination of their mechanistic and genetic aspects.

Interactions between microbiome and underlying mechanisms in asthma

Microbiome primes host innate immunity in utero and play fundamental roles in the development, training, and function of the immune system throughout the life. Interplay between the microbiome and immune system maintains mucosal homeostasis, while alterations of microbial community dysregulate immune responses, leading to distinct phenotypic features of immune-mediated diseases including asthma. Microbial imbalance within the mucosal environments, including upper and lower airways, skin, and gut, has consistently been observed in asthma patients and linked to increased asthma exacerbations and severity. Microbiome research has increased to uncover hidden microbial members, function, and immunoregulatory effects of bacterial metabolites within the mucosa. This review provides an overview of environmental and genetic factors that modulate the composition and function of the microbiome, and the impacts of microbiome metabolites and skin microbiota on immune regulation in asthma.

Breastfeeding in infancy and mortality in middle and late adulthood: A prospective cohort study and meta-analysis

BACKGROUND

Breastfeeding in infancy is associated with a lower risk of mortality among children, but the impact on mortality in middle and late adulthood remains unknown.

OBJECTIVES

To assess the association between breastfeeding in infancy and mortality in middle and late adulthood.

METHODS

We included 383,627 participants aged 40-73 from the UK Biobank (2006-2010) and followed up until 2021. Hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause and cause-specific mortality according to breastfeeding in infancy were estimated with Cox proportional hazards regression models. We further did a meta-analysis, including results from our present study and three other cohort studies (PROSPERO; number CRD42022348925).

RESULTS

During a total of 4732,751 person-years of follow-up, 25,581 deaths were identified. Breastfeeding in infancy was associated with lower risks of mortality in middle and late adulthood, with adjusted HRs (95% CIs) of 0.95 (0.93-0.98) for all-cause mortality; 0.91 (0.87-0.96) for cardiovascular mortality and 0.94 (0.874-0.999) for respiratory mortality. Specifically, the association with mortality seemed to attenuate with age - stronger in middle-aged adults than in older adults. A similar association between breastfeeding in infancy and all-cause mortality was found in the meta-analysis.

CONCLUSION

Breastfeeding in infancy is associated with a lower risk of mortality - even decades later - in middle and late adulthood.

Exclusive Breastfeeding and Childhood Morbidity: A Narrative Review

Globally, diarrheal diseases and acute respiratory infections are the leading causes of morbidity and mortality in children under 5 years old. The benefits of exclusive breastfeeding in reducing the risk of gastrointestinal and respiratory infections are well documented. Optimal breastfeeding may potentially save the lives of about 800,000 children in low-income settings. Despite the evidence, around 63% of infants from birth to 6 months are not exclusively breastfed worldwide. We searched the literature published between 2010 and 2022 in Medline, Embase, and Scopus on the association between exclusive breastfeeding and infectious diseases. We selected and reviewed 70 relevant studies. Our findings expand and confirm the positive association between exclusive breastfeeding and reduced risk of a number of gastrointestinal, respiratory, and other infections in 60 out of 70 studies observed in both low- and high-income settings. Several studies analyzing exclusive breastfeeding duration reported that a longer exclusive breastfeeding duration is protective against many infectious diseases. This review also reported a lack of standardized definition for measuring exclusive breastfeeding in many studies. Overall, the results highlight the benefits of exclusive breastfeeding in many studies and suggests reporting exclusive breastfeeding in future studies using a consistent definition to enable better monitoring of exclusive breastfeeding rates.

Association between History of Prolonged Exclusive Breast-Feeding and the Lung Function Indices in Childhood

Although the propitious effects of breastfeeding on children's health are indisputable, the impact of exclusive breastfeeding on the lung function later in life remains controversial. Our objective was to explore the possible associations between breastfeeding and the lung function of children who were exclusively breastfed for an extensive period of time. This was a cross-sectional study of children who were exclusively breastfed for more than 12 months. Demographics and anthropometric data were collected; the body mass index (BMI), % body fat, and % central obesity were calculated; and all the participants underwent standard spirometry with reversibility testing. The relationship between breastfeeding duration and spirometric parameters was assessed by Spearman's correlation and multivariable regression, after adjustment for other confounders. Forty-six children (21 boys), aged 9.2 ± 2.4 years, with a reported breastfeeding duration of 27.5 ± 12.5 months (range 12-60 months) were included; 13% were overweight (none were obese) and 21.7% had central obesity. The average FEV1 was 104.7 ± 10.4% and the average FEF25-75 was 107.9 ± 13.3%. The duration of exclusive breastfeeding was positively correlated with FEF25-75% (r = 0.422, p = 0.003). Multivariable linear regression analysis confirmed the above finding (beta coefficient 0.478, p = 0.002), independently of age, overweight, and central obesity. No correlation was noted between the duration of breastfeeding and other spirometric parameters. In addition to its favorable impact on the metabolic profile, prolonged exclusive breastfeeding seems to exert a propitious effect on the function of smaller airways throughout childhood.

Microbial dysbiosis and childhood asthma development: Integrated role of the airway and gut microbiome, environmental exposures, and host metabolic and immune response

Asthma is a chronic and heterogeneous respiratory disease with many risk factors that typically originate during early childhood. A complex interplay between environmental factors and genetic predisposition is considered to shape the lung and gut microbiome in early life. The growing literature has identified that changes in the relative abundance of microbes (microbial dysbiosis) and reduced microbial diversity, as triggers of the airway-gut axis crosstalk dysregulation, are associated with asthma development. There are several mechanisms underlying microbial dysbiosis to childhood asthma development pathways. For example, a bacterial infection in the airway of infants can lead to the activation and/or dysregulation of inflammatory pathways that contribute to bronchoconstriction and bronchial hyperresponsiveness. In addition, gut microbial dysbiosis in infancy can affect immune development and differentiation, resulting in a suboptimal balance between innate and adaptive immunity. This evolving dysregulation of secretion of pro-inflammatory mediators has been associated with persistent airway inflammation and subsequent asthma development. In this review, we examine current evidence around associations between the airway and gut microbial dysbiosis with childhood asthma development. More specifically, this review focuses on discussing the integrated roles of environmental exposures, host metabolic and immune responses, airway and gut microbial dysbiosis in driving childhood asthma development.

The relationship between the gut microbiome and the risk of respiratory infections among newborns

Background

Emerging evidence points to a critical role of the developing gut microbiome in immune maturation and infant health; however, prospective studies are lacking.

Methods

We examined the occurrence of infections and associated symptoms during the first year of life in relation to the infant gut microbiome at six weeks of age using bacterial 16S rRNA V4-V5 gene sequencing (N = 465) and shotgun metagenomics (N = 185). We used generalized estimating equations to assess the associations between longitudinal outcomes and 16S alpha diversity and metagenomics species.

Results

Here we show higher infant gut microbiota alpha diversity was associated with an increased risk of infections or respiratory symptoms treated with a prescription medicine, and specifically upper respiratory tract infections. Among vaginally delivered infants, a higher alpha diversity was associated with an increased risk of all-cause wheezing treated with a prescription medicine and diarrhea involving a visit to a health care provider. Positive associations were specifically observed with Veillonella species among all deliveries and Haemophilus influenzae among cesarean-delivered infants.

Conclusion

Our findings suggest that intestinal microbial diversity and the relative abundance of key taxa in early infancy may influence susceptibility to respiratory infection, wheezing, and diarrhea.