Previous studies have found that allergic and non-allergic infants have different intestinal microbial colonisation patterns, but the microbial signature behind the pathogenesis of allergies is still unclear.
A study was hence conducted to better understand how intestinal microbiota develops in healthy and allergic infants.
The study involved researchers from Singapore (Danone Nutricia Early Life Nutrition, A*STAR, the National University of Singapore, KK Women's and Children's Hospital), the UK (the University of Southampton), and the Netherlands (Nutricia Research, the University of Groningen, Wageningen University).
They sought to identify potential microbiota biomarkers of allergies via a case-control study of a Chinese sub-cohort within GUSTO (Growing Up in Singapore Towards Healthy Outcomes), Singapore's largest and most comprehensive birth cohort study.
Colonisation and composition
The intestinal microbial composition and diversity of 18 healthy and 21 allergic infants were assessed at three weeks, three months and six months of age, then correlated with their allergy status at 18 and 36 months of age.
The researchers observed "pronounced differences in intestinal microbiota composition between allergic and healthy infants" at three months of age.
The healthy infants' intestines were colonised by a greater abundance of commensal Bifidobacterium, while an opportunistic pathogen called Klebsiella was "significantly enriched in the allergic infants".
At three months of age, Klebsiella colonisation stayed consistent in approximately half the allergic infants, but decreased considerably in the healthy infants.
Conversely, Bifidobacterium colonisation in the allergic infants was significantly lower than in the healthy infants at the same age.
The infants who had a high Klebsiella / Bifidobacterium (K/B) ratio at three months old were also found to have higher odds of developing allergies by the time they were 18 months to three years old.
The study highlighted a relationship between a high K/B ratio in early infancy and the occurrence of allergies later in childhood.
The researchers stated: "Our study postulates that an elevated K/B ratio in early infancy could be a potential indicator of an increased risk of allergy development.
"This line of research might enable future intervention strategies in early life to prevent or treat allergy."
Intestinal microbiota alteration has been connected to inflammation, which contributes to the development of non-communicable diseases, including allergic diseases.
Klebsiella bacteria "are associated with induction of pro-inflammatory responses in the host", while Bifidobacterium increases resistance to intestinal pathogens, preventing allergy and inflammation.
Intestinal Klebsiella colonisation is not rare in infants, but commensal intestinal bacteria usually provide a counter. However, antibiotic intake or pathological factors can reduce commensal bacteria, causing pathogens to outnumber them.
However, in past research, Bifidobacterium has displayed antimicrobial activity against Klebsiella.
Factors for the future
The researchers said the study's small sample size (consisting of purely Chinese infants) meant they could not fully investigate other possible factors in allergy development, including antibiotic use, family environment, maternal microbiota, mode of birth and infant feeding patterns.
They said future research should take into account other risk factors, involve a larger sample size, and assess allergic infants' microbiota profiles using well-characterised allergic phenotypes.
They concluded: "A system biology approach encompassing microbiota / microbiome, human genetics / epigenetics would also be a great direction for future studies aiming to disentangle complex diseases such as allergy."
Source: Beneficial Microbes
"Ratio of Klebsiella/Bifidobacterium in early life correlates with later development of paediatric allergy"
Authors: JSY Low, et al.