marginally significantP = 0·052
on, median) was 2·73 (0·30, 2·73) log 10 c.f.u./ml in G1 (no samples were positive in G2). Results of mathematical and statistical modeling In the univariate analysis, the effect of environmental contamination level significantly influenced the transmission rate ( P = 0·0002), the group effect was marginally significant ( P = 0·052) and the strain effect was not significant.