A major Finnish cohort study reveals that subtle changes in maternal and infantile intestinal bacteria could point out a higher risk of respiratory infections in babies, highlighting new avenues for prevention at the start of life.
Study: The association of maternal and infantile intestinal microbiota with respiratory infections in infants. Image credit: New Africa / Shutterstock
In a recent article published in the journal Pediatric researchResearchers in Finland have studied if the composition of the intestinal microbiota in mothers and young infants is linked to the risk of developing a respiratory tract infection (RTI) during the first six months of infants.
They found that infants with RTI had differences in the relative abundance of specific bacterial taxa compared to those without, while global alpha and beta diversity has remained similar. Microbial communities in mothers have also shown differences.
Background
RTIs are common in early childhood. Healthy infants and ultimately high -income countries experience four to ten episodes during their first year. These infections affect the well-being of infants and have social and economic consequences. They can increase parental stress and cause missed work.
Interest increases in the way in which the early intestinal microbiota could influence sensitivity to RTI. Animal studies suggest that intestinal microbes shape respiratory immunity. However, the results of the human study remain inconsistent.
Certain research connects a low microbial diversity and a beneficial intestinal bacteria reduced with higher risks of whistling and asthma in childhood. Important bacteria include Bifidobacterium, Faecalibacterium, Ruminocoqueet Road pink.
However, we know much less about direct associations between the intestinal microbiota and the RTI in early childhood, largely because longitudinal studies with standardized monitoring of infections and the sampling of early stools are limited.
Most previous studies have focused on subsequent results, such as asthma, rather than acute RTI at the start of life. In addition, the maternal microbiota, which can influence the infant’s intestinal microbiome, has rarely been examined.
About the study
The researchers hypothesized that the early intestinal microbiota, as well as the maternal microbiota, could be associated with the occurrence of RTI during the first six months of life. They used an imbalanced case-testimony which included Finnish infants not Twin in the term healthy with a birth weight of at least 2.5 kg.
RTI cases have been defined as infants who have developed a higher RTI with fever, average otitis or RTI lower than the first six months of life. Families have recorded symptoms of infection and medical visits in an online diary in the first four months and bihebdomedary up to seven months, allowing precise monitoring of RTIs.
Feccal samples were taken from mothers around their due date and infants at the age of three and six weeks. The samples were immediately frozen at home and treated later for DNA extraction and sequencing the 16S RNA gene to characterize the composition of the microbiota.
Out of 1052 infants from the Helsinki cohort, 189 developed RTI in the six months. Microbiota data were available for 178 infants and 136 mothers from the RTI group, and for 143 infants and 125 mothers from the control group, totaling 461 infants and 261 maternal samples.
The analyzes compared microbial diversity (alpha and beta) and the relative abundance of bacterial taxa between groups. Sensitivity analyzes have excluded infants with infections before sampling of stools and cases and controls paired by relevant factors (birth, sex and mode of administration).
Key conclusions
Among 178 infants who developed an RTI in the first six months and 143 witnesses, the median duration of RTI was 11 days. Most cases were higher RTI with fever (49%) or average otitis (47%), while only 4%were low.
About 30% of RTI cases occurred in the first three months, most often the average otitis. More than half of the affected infants visited a doctor and 14% required emergency care, while much fewer checks have had medical visits.
In the maternal microbiota, global diversity and wealth did not differ between groups, but mothers of infants with RTIS had a higher abundance of Citrobacter, Enterobacteret Enterococcuswhile Clostridium was lower. These bacteria were described by the authors as opportunistic pathogens, which suggests that maternal microbial instability could play a role in developing infant risk.
For infants, the global microbial composition at 3 and 6 weeks was similar between groups. However, at three weeks, those who later developed RTI showed higher levels of several bacterial families (such as Rikenellaceae, Prevotellaceae and Verrucomicrobiaceae) and genres, including, including Alistipes, Akkermansia, Faecalibacterium, Peptoniphiluset Serratia. The higher abundance of Faecalibacterium was notable because previous studies had often linked lower levels of this kind to respiratory problems, highlighting a potential contradiction with previous results.
At six weeks old, prevotellaceae remained high in infants who developed RTI in the three months, while reducing AnaerostipesAnother butyrate producer has been observed. Anaerostipes Exhaustion can modify the metabolism of lactate and butyrate, with possible effects on immune function.
Sensitivity analyzes have confirmed these results, showing associations consistent with higher abundance of gender producers (Pseudobutyrivibrio, Faecalibacteriumet Road pink), et Proteusand lower Veillonella et Anaerostipes In infants who have developed RTI.
Comparison between mothers of infants who have developed an episode of respiratory tract infection (RTI) during the first 6 months of life and mothers of infants selected at random without an episode of infection. PCOA plots based on the Dissemblances of Bray-Curtis samples, showing the richness of the microbiota as a background (and). The clusters are presented by circles, which have been drawn according to the standard deviations of data points in each category of samples (and). Comparisons is between mothers of infants who have developed an RTI in the first 6 months of life and mothers of infants remaining healthy (p = 0.39). The column graphics stacked in cluster show differences in microbiota in the family (b). Comparisons are between mothers of infants who have developed an RTI in the first 6 months of life (yes) and the remaining infant mothers (no).
Conclusions
In conclusion, the composition of the maternal and early intestinal microbiota for infants can influence early sensitivity to RTI, highlighting potential targets for preventive interventions in future studies. The authors stressed that these are associations, and not proof of causation, and that the analysis was exploratory with a fake discovery rate (FDR) of 0.1. They also proposed that the early appearance of adult butyrate producers, such as Faecalibacterium et Road pinkCould represent a “premature maturation of the intestinal microbiota” which predisposes infants to infection.
The forces of this analysis include the large longitudinal birth cohort, the systematic parental relationship of light RTIs and the analysis of samples for infants and maternal. However, the limits imply the relatively homogeneous population, high income, universal breastfeeding and restriction to healthy and term infants, limiting generalization.
Note
Some microbial associations (for example, with Faecalibacterium, Road pinket Pseudobutyrivibrio) were the most obvious in sensitivity analyzes which excluded infants with early and paired infections from witnesses by perinatal factors. These were not always present in the main unrivaled analysis. Readers must interpret these results as exploratory associations rather than coherent causal signals.
