Gut microbiota associated with higher asthma rates among Black children with food allergy

Key takeaways:

• Children with asthma had more Bacteroides stercoris and Bacteroides acidifaciens.
• Black children had more Bacteroides thetaiotaomicron and Bacteroides eggerthii than white children.

Variations in gut microbiota between Black children and white children may have a role in higher rates of asthma among Black children who have food allergy, according to a study published in The Journal of Allergy and Clinical Immunology.

Mahboobeh Mahdavinia, MD, PhD, chief of the division of allergy and immunology in the departments of medicine and pediatrics at Rush University Medical Center, and colleagues conducted a prospective cohort study that included 122 white children (mean age, 4.87 years; 63% boys) and 30 Black children (mean age, 6.84 years; 57% boys) aged younger than 12 years with an allergist-diagnosed mediated food allergy.

The most common food allergies included peanut (62.5%), tree nuts (51.5%) and egg (31.2%), with 92% diagnosed with more than one food allergy.

Mahboobeh Mahdavinia

Also, 25.4% of the white children and 73.3% of the Black children had asthma (P < .001). Black children in the cohort were significantly older than the white children (P = .006), but there were no significant differences between the groups based on birth delivery methods or use of antibiotics during pregnancy or delivery.

Stool samples indicated no racial differences in the overall bioburden of bacteria, nor were there any significant differences associated with race or age based on the Chao1 diversity index. But the stool samples of the Black children had significantly higher scores based on the Shannon diversity index (P = .02).

In an analysis using the Spearman correlation coefficient (r), an increase in Shannon index with age (r = 0.34; P < .001) suggested that evenness in microbiota diversity increases with age, according to the researchers. In fact, when controlling for age in a generalized linear model, researchers observed an attenuated racial difference in Shannon diversity (P < .001).

There were significant variations in the relative abundance of several taxa across age groups, the researchers found, with children aged 3 years and younger exhibiting the most variability in their gut microbiota composition.

Children aged older than 3 years had higher relative abundance of Bifidobacterium breve, Bacteroides acidifaciens, Bacteroides intestinalis and Veillonella spp. Children aged younger than 3 years had higher relative abundance of Bacteroides stercoris, Bacteroides eggerthii, Bifidobacterium catenulatum and Bacteroides salyersiae.

There were no racial differences in overall bacteria bioburden, the researchers continued, but there were differences in relative abundance of several taxa between Black and white children that remained significant after adjustments for age.

Noting the significant variations in gut microbiota among children aged younger than 3 years, the researchers repeated their analyses of race and relative abundances of bacteria among 70 white and 22 Black children aged 3 to 12 years.

Relative abundances of Bacteroides thetaiotaomicron, Chlamydia trachomatis, Parabacteroides goldsteinii, Prevotella copri and B. eggerthii were significantly higher in the stool of Black children.

Also, relative abundances of Bifidobacterium sp. CAG:754, Parabacterium johnsonii, B. intestinalis, B. breve and B. acidifaciens were significantly lower in Black children.

Overall, analyses adjusted for race, age and center showed that the relative abundance of bacteria was linked to lifetime history of asthma and eczema.

Specifically, lower relative abundances of B. breve, B. catenulatum, P. copri, Veilloella sp. CAG:933, Bacteroides plebeius and Lachnospira pectinoschiza and higher relative abundances of B. stercoris, B. acidifaciens and Blautia obeum were associated with asthma.

Lower relative abundances of Bacteroides faecis, Ruminococcus torques, Blautia wexlerae and Clostridium leptum and higher relative abundances of B. stercoris and Flavonifractor plautii were associated with lifetime history of eczema.

Further analysis revealed a trend toward significance between race and gut microbiota alpha diversity as measured by Shannon index once adjusted for asthma, with no impact when eczema was included in the model.

Bifidobacterium and Bacteroides, which were the species of bacteria with the most significant differential relative abundance, had a significant mediation effect on the association between asthma and race, the researchers found.

The estimated regression coefficient for the effect of Bifidobacterium genera was 0.354 (95% CI, 0.233-0.486). Also, B. breve had the most significant negative association with asthma in Black children (–0.072; 95% CI, –0.141 to –0.004) of the six Bifidobacterial taxa that were tested.

Overall, the researchers said that the relative abundances of several important bacteria in white children and Black children exhibited specific differences, with a trend toward less diverse gut microbiota among Black children indicating an association between bacterial diversity and race linked to the presence of other comorbid asthma.

Specifically, the researchers continued, variations in the relative abundances of Bacteroides and Bifidobacterium species in Black children along with their histories of asthma suggest they have a role in higher rates of asthma among Black children with food allergy.