Clostridium Abundance and Lower Weight-for-Age z Scores Among 6-Month-Old Infants: Nested Cross-Sectional Study

The gut microbiota plays a crucial role in infant nutrition through its effects on energy metabolism, nutrient absorption, and immune regulation. However, evidence from Indonesian infants remains limited.

This study aimed to examine the association between genus-level gut microbiota abundance and weight-for-age z scores (WAZ) among 6-month-old infants in coastal Banggai District, Central Sulawesi, Indonesia.

We conducted a nested follow-up cross-sectional observational analysis of 88 six-month-old infants, including 42 (47.7%) who were born to mothers who were assigned to receive Moringa oleifera enriched with royal jelly group and 46 (52.3%) who were assigned to receive a multiple micronutrient supplement in a previous maternal supplementation trial. Maternal and infant characteristics were collected via structured interviews and standardized anthropometric measurements. WAZ was calculated using the World Health Organization Child Growth Standards, and underweight (WAZ <-2 SD) was reported as a secondary indicator. Stool samples were analyzed using genus-specific quantitative polymerase chain reaction to quantify Bifidobacterium, Lactobacillus, Bacteroides, Clostridium, and Escherichia coli (log10 colony-forming unit/mL). Associations between bacterial abundance and WAZ were assessed using multivariable linear regression adjusted for maternal supplementation allocation and relevant maternal, environmental, and infant covariates.

The pooled mean WAZ was -0.47 (SD 1.09), and 8% (7/88) of the infants were underweight. The combined abundance of beneficial genera was higher than that of opportunistic bacteria (E coli and Clostridium; Wilcoxon signed-rank test; P=.002). Higher Clostridium abundance was inversely associated with WAZ (unadjusted β=-.094, 95% CI -0.173 to -0.015; P=.02; adjusted β=-.091, 95% CI -0.172 to -0.010; P=.03). No statistically significant associations were observed for Bifidobacterium (P=.13), Lactobacillus (P=.19), Bacteroides (P=.70), or E coli (P=.18) in adjusted models.

Among 6-month-old infants in coastal Central Sulawesi, higher genus-level Clostridium abundance was independently associated with lower WAZ. Given the cross-sectional design and genus-level quantitative polymerase chain reaction assessment, temporality and species-level mechanisms cannot be established. Longitudinal studies using more comprehensive microbiome profiling are warranted to clarify potential pathways linking gut microbiota and early-life growth.