The factors that influence the makeup of the gut microbiota and its consequences on common pediatric diseases are still little known, particularly in low-income settings. The study sought to determine if illness predicts gut microbiota composition in Malawian children, as well as whether the microbiome predicts further morbidity. Researchers hypothesized that common infectious illness symptoms would be associated with reduced microbiota maturity and diversity. They analyzed data from 631 participants in a randomized-controlled nutrition intervention study in which pregnant and nursing women and their children aged 6 to 18 months received a small-quantity lipid-based nutritional supplement. The children’s feces were collected at 6, 12, 18, and 30 months of age and examined using 16S rRNA sequencing. Microbiota characteristics included microbiota diversity (Shannon Index), microbiota maturity (microbiota-for-age z score), and taxonomic relative abundances. Variables associated with morbidity included gastrointestinal and respiratory symptoms, as well as fever.

Diarrhea and respiratory symptoms from 11 to 12 months were associated with a lower microbiota-for-age z score and a higher Shannon Index (P=0.035 and P=0.023, respectively). At all time periods, morbidity before sample collection predicted the relative abundances of numerous bacterial species. Higher microbiota maturity and diversity at 6 months predicted a decreased incidence rate of fever in the next 6 months (P=0.007 and P=0.031, respectively).

In conclusion, the data do not support the notion that morbidity prevalence predicts a decline in gut microbiota maturity or variety in rural Malawian children. Certain morbidity symptoms may predict microbiota maturity, diversity, and relative abundances of certain bacterial taxa. Furthermore, the variety and maturity of the microbiota may be linked to the eventual occurrence of fever.