Table 1.
Comparative detection of Salmonella Infantis ATCC 51741 in 25 g dry dog food test portions by the LAMP method versus the FDA BAM Chapter 5 reference method in an unpaired study design.
| Collaboratora | Number of positive samples/number of samples tested (probability of detection, POD) among dry dog food test portionsb | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Uninoculated control (0 MPN/25 g) | Low-level inoculation (0.65 MPN/25 g) | High-level inoculation (3.01 MPN/25 g) | |||||||
| LAMP presumptive | LAMP final | BAM reference | LAMP presumptive | LAMP final | BAM reference | LAMP presumptive | LAMP final | BAM reference | |
| 1 | 0/8 (0) | 0/8 (0)c | 0/8 (0) | 4/8 (0.5) | 4/8 (0.5) | 6/8 (0.75) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 2 | 6/8 (0.75) | 1/8 (0.13) | 0/8 (0) | 7/8 (0.88) | 5/8 (0.63) | 6/8 (0.75) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 3 | 0/8 (0) | 0/8 (0) | 0/8 (0) | 6/8 (0.75) | 6/8 (0.75) | 2/8 (0.25) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 4 | 6/8 (0.75) | 2/8 (0.25) | 1/8 (0.13) | 8/8 (1) | 6/8 (0.75) | 5/8 (0.63) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 5 | 1/8 (0.13) | 0/8 (0) | 0/8 (0) | 4/8 (0.5) | 3/8 (0.38) | 6/8 (0.75) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 6 | 0/8 (0) | 0/8 (0) | 0/8 (0) | 4/8 (0.5) | 4/8 (0.5) | 5/8 (0.63) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 7 | 0/8 (0) | 0/8 (0) | 0/8 (0) | 2/8 (0.25) | 2/8 (0.25) | 6/8 (0.75) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 8 | 0/8 (0) | 0/8 (0) | 0/8 (0) | 5/8 (0.63) | 5/8 (0.63) | 4/8 (0.5) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 9 | 0/10 (0) | 0/10 (0) | 0/6 (0) | 4/5 (0.8) | 3/5 (0.6) | 5/11 (0.45) | 9/9 (1) | 9/9 (1) | 7/7 (1) |
| 10 | 0/6 (0) | 0/6 (0) | 0/10 (0) | 3/9 (0.33) | 3/9 (0.33) | 7/7 (1) | 9/9 (1) | 9/9 (1) | 7/7 (1) |
| 11 | 0/8 (0) | 0/8 (0) | 0/8 (0) | 6/8 (0.75) | 6/8 (0.75) | 5/8 (0.63) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 12 | 0/8 (0) | 0/8 (0) | 0/8 (0) | 4/8 (0.5) | 4/8 (0.5) | 2/8 (0.25) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 13 | 0/8 (0) | 0/8 (0) | 0/8 (0) | 5/8 (0.63) | 5/8 (0.63) | 4/8 (0.5) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| 14 | 0/8 (0) | 0/8 (0) | 0/8 (0) | 4/8 (0.5) | 3/8 (0.38) | 6/8 (0.75) | 8/8 (1) | 8/8 (1) | 8/8 (1) |
| All | 13/112 (0.12) | 3/112 (0.03) | 1/112 (0.01) | 66/110 (0.6) | 59/110 (0.54) | 69/114 (0.61) | 114/114 (100) | 114/114 (100) | 110/110 (100) |
| Finald | 1/96 (0.01) | 0/96 (0) | 0/96 (0) | 51/94 (0.54) | 48/94 (0.51) | 58/98 (0.59) | 98/98 (100) | 98/98 (100) | 94/94 (100) |
a Collaborators 1 and 2 were from the same laboratory, so were collaborators 3 and 4, 5 and 6, 7 and 8, 9 and 10, 11 and 12, 13 and 14. b The LAMP presumptive column shows the results when LAMP samples were tested by LAMP (including false positive results). The LAMP final column shows the results when combining the LAMP presumptive and LAMP confirmed by BAM results (data not shown) to exclude false positive and false negative results, i.e., only LAMP samples tested positive by both LAMP and BAM confirmation were included. The BAM reference column shows the results when BAM samples were tested by BAM. c One sample was confirmed positive by BAM. The LAMP final result excluded this sample as it was negative by LAMP. d The Final row excluded data from collaborators 2 and 4 due to culture-confirmed positives in uninoculated test portions.