Table 3.

Relationship of clinical factors to predominant taxa (class level)

VariableGA at birth (wk)BacilliClostridiaGammaproteobacteria
Day of life<26−0.007 (−0.011, −0.004)0.007 (0.004, 0.011)0.000 (−0.004, 0.004)
26–28−0.007 (−0.010, −0.003)0.009 (0.005, 0.012)0.000 (−0.005, 0.003)
>28−0.010 (−0.014, −0.006)0.010 (0.005, 0.014)0.000 (−0.004, 0.005)
Days on antibiotics*<260.004 (−0.005, 0.013)−0.012 (−0.021, −0.003)0.009 (0.000, 0.0182)
26–28−0.001 (−0.011, 0.010)−0.016 (−0.026, −0.005)0.017 (0.006, 0.027)
>28−0.012 (−0.031, 0.007)−0.008 (−0.027, 0.012)0.021 (0.002, 0.040)
Breast milk<26−0.045 (−0.116, 0.026)−0.031 (−0.102, 0.040)0.073 (0.001, 0.143)
26–28−0.080 (−0.185, 0.025)−0.048 (−0.153, 0.0577)0.115 (0.010, 0.221)
>28−0.016 (−0.101, 0.070)−0.074 (−0.159, 0.012)0.079 (−0.007, 0.164)
C-section<26−0.187 (−0.346, −0.028)−0.011 (−0.171, 0.148)0.201 (0.042, 0.360)
26–280.226 (0.027, 0.425)0.010 (−0.189, 0.209)−0.089 (−0.289, 0.110)
>280.212 (−0.017, 0.441)0.021 (−0.208, 0.249)−0.083 (−0.312, 0.146)
Sampled after 01/01/2011<260.266 (0.131, 0.401)−0.151 (−0.286, −0.016)−0.140 (−0.275, −0.005)
26–280.037 (−0.178, 0.252)−0.159 (−0.373, 0.056)−0.129 (−0.344, 0.086)
>280.063 (−0.129, 0.254)−0.049 (−0.240, 0.142)−0.039 (−0.231, 0.152)
  • A mixed model regression analysis investigated the relationship between clinical variables and taxa fractional abundance in repeated samples of subjects, by gestational age group. Statistically significant linear trends are indicated by arrows. Values are beta coefficients with 95% confidence intervals. Negative values indicate taxa decrements and positive values indicate taxa increments per unit increase in predictor variable. Significant decrease in taxa, P < 0.05; Significant increase in taxa, P < 0.05. GA, gestational age at birth.

  • * Percent of days of life antibiotics were administered before each specimen.

  • Breast milk (BM) categorized by volume (0,0%; 1, <10%; 2,10–50%; 3, >50% of enteral volume).

  • Samples collected in first half of study or second half; positive values represent greater representation in second half.