Prenatal household size and composition are associated with infant fecal bacterial diversity in Cebu, Philippines.

OBJECTIVES: The gut microbiome (GM) connects physical and social environments to infant health. Since the infant GM affects immune system development, there is interest in understanding how infants acquire microbes from mothers and other household members. MATERIALS AND METHODS: As a part of the Cebu Longitudinal Health and Nutrition Survey (CLHNS), we paired fecal samples (proxy for the GM) collected from infants living in Metro Cebu, Philippines at 2 weeks (N = 39) and 6 months (N = 36) with maternal interviews about prenatal household composition. We hypothesized that relationships between prenatal household size and composition and infant GM bacterial diversity (as measured in fecal samples) would vary by infant age, as well as by household member age and sex. We also hypothesized that infant GM bacterial abundances would differ by prenatal household size and composition. RESULTS: Data from 16 S rRNA bacterial gene sequencing show that prenatal household size was the most precise estimator of infant GM bacterial diversity, and that the direction of the association between this variable and infant GM bacterial diversity changed between the two time points. The abundances of bacterial families in the infant GM varied by prenatal household variables. CONCLUSIONS: Results highlight the contributions of various household sources to the bacterial diversity of the infant GM, and suggest that prenatal household size is a useful measure for estimating infant GM bacterial diversity in this cohort. Future research should measure the effect of specific sources of household bacterial exposures, including social interactions with caregivers, on the infant GM.

The effects of collection and storage conditions in the field on salivary testosterone, cortisol, and sIgA values.

AIM: To determine if field-typical storage and collection conditions are related to salivary testosterone (T), cortisol (cort) and secretory immunoglobulin A (sIgA) as measured using commercially available kits. SUBJECTS AND METHODS: This study assessed whether storage time (∼6 months to 1.5 years) at -35 °C impacted levels of the measured biomarkers (n = 10,247 samples). For a sub-set of T samples (n = 2954), we also evaluated the impact of collection conditions, such as time spent at room temperature in participants' homes (0-39 hours) and time spent in coolers (0.3-10 hours) in transit. RESULTS: T was unrelated to storage and collection variables and there was no evidence of reduced sample fidelity at longer storage times. Cort samples stored at -35 °C for longer had significantly lower values, but the effect was small (ß = -0.003 nmol/L/day, SE <0.001, p = 0.005). sIgA trended higher with longer storage at -35 °C (ß = 0.84 µg/mL/day, SE = 0.45, p = 0.063). Collection and storage time variables did not improve the fit of any of the models except the one that evaluated cortisol. CONCLUSIONS: Salivary T was unaffected by extended storage at -35 °C and only a weak relationship was found between storage time and salivary cort or sIgA. Findings underscore the robustness of these biomarkers under field-typical freezer storage conditions.