Table 2.
Proportion of matched milk at point of purchase and infant food samples by categorical change in microbial contamination.
| Overall | UHT | Fresh pasteurized | Un-packaged | p-valuea | |
|---|---|---|---|---|---|
| Sample size (all assays) | 187 | 132 | 36 | 19 | |
| E. aerogenes | |||||
| Not detected in either sample | 0.53 | 0.58 | 0.53 | 0.16 | 0.000 |
| 95% CI | (0.45, 0.60) | (0.49, 0.66) | (0.36, 0.70) | (−0.02, 0.34) | |
| Lower in infant food than vendor milk | 0.11 | 0.02 | 0.17 | 0.58 | 0.000 |
| 95% CI | (0.06, 0.15) | (0.00, 0.05) | (0.04, 0.29) | (0.33, 0.82) | |
| Higher in infant food than vendor milk | 0.37 | 0.40 | 0.31 | 0.26 | |
| 95% CI | (0.30, 0.44) | (0.32, 0.49) | (0.15, 0.46) | (0.05, 0.48) | |
| S. enterica | |||||
| Not detected in either sample | 0.87 | 0.90 | 0.92 | 0.53 | 0.000 |
| 95% CI | (0.82, 0.92) | (0.85, 0.95) | (0.82, 1.01) | (0.28, 0.77) | |
| Lower in infant food than vendor milk | 0.06 | 0.02 | 0.06 | 0.42 | 0.001 |
| 95% CI | (0.03, 0.10) | (−0.01, 0.04) | (−0.02, 0.13) | (0.18, 0.67) | |
| Higher in infant food than vendor milk | 0.07 | 0.08 | 0.03 | 0.05 | |
| 95% CI | (0.03, 0.11) | (0.04, 0.13) | (−0.03, 0.08) | (−0.06, 0.16) | |
| S. sonnei | |||||
| Not detected in either sample | 0.73 | 0.77 | 0.81 | 0.32 | 0.000 |
| 95% CI | (0.66, 0.79) | (0.69, 0.84) | (0.67, 0.94) | (0.09, 0.55) | |
| Lower in infant food than vendor | 0.07 | 0.00 | 0.06 | 0.63 | 0.000 |
| 95% CI | (0.04, 0.11) | (0.00, 0.00) | (−0.02, 0.13) | (0.39, 0.87) | |
| Higher in infant food than vendor milk | 0.20 | 0.23 | 0.14 | 0.05 | |
| 95% CI | (0.14, 0.25) | (0.16, 0.31) | (0.02, 0.26) | (−0.06, 0.16) | |
| EHEC 0157 phenotype b | |||||
| Not detected in either sample | 0.45 | 0.49 | 0.44 | 0.11 | 0.000 |
| 95% CI | (0.38, 0.52) | (0.41, 0.58) | (0.27, 0.61) | (−0.05, 0.26) | |
| Lower in infant food than vendor | 0.12 | 0.03 | 0.14 | 0.74 | 0.000 |
| 95% CI | (0.08, 0.17) | (0.00, 0.06) | (0.02, 0.26) | (0.52, 0.95) | |
| Higher in infant food than vendor milk | 0.41 | 0.47 | 0.42 | 0.05 | |
| 95% CI | (0.34, 0.49) | (0.38, 0.56) | (0.25, 0.59) | (−0.06, 0.16) | |
The one infant formula sample is excluded.
a
p-values refer to probability that the proportions for the respective rows or sets of rows (not detected in either sample; lower vs. higher in infant food than vendor milk) are equal across milk types, based on Fisher's exact test.
b
Phenotype as indicated by culture analysis; the identity of these organisms could not be confirmed through PCR analysis.