Table 4.
Detection of spiked pathogenic E. coli on four different food matrices using the CoSYPS Path E. coli detection system
| Sample | Matrix | Spiked strain | Serotype | Expected positives | Inoculum cfu/25 g | qPCR assay of the CoSYPS Path E. coli | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| uidA-3 | uidA-7 | ipaH-569 | ipaH-3 | eae-185 | eae-EBP1 | stx1and2–4 | stx1–185 | stx2–81-alt | aggR-185 | aggR-2 | aaiC-EBP1 | aaiC-EBP2 | ||||||
| Positive control | na | na | na | all | na | + | + | + | + | + | + | + | + | + | + | + | + | + |
| No-template control | na | None | na | None | na | – | – | – | – | – | – | – | – | – | – | – | – | – |
| D-6-Tomato | Tomato | TIAC 1863 | O91:H21 | stx2 | 48 ± 4 | +(13.7) | +(13.7) | – | – | - * | – | +(14.7) | – | +(13.5) | – | – | - * | – |
| D-7-Tomato | 5 ± 1 | +(15.5) | +(15.0) | – | – | – | – | +(16.8) | – | +(15.2) | – | – | – | – | ||||
| Blank-Tomato | None | - (33.2) | - (34.4)* | – | – | – | – | – | – | - * | – | – | – | – | ||||
| D-6-Salami | Salami | TIAC 2096 | O157:H7 | eae/stx2 | 27 ± 15 | +(18.1) | +(18.6) | – | – | +(18.7) | +(19.2) | +(18.8) | – | +(17.0) | – | – | – | – |
| D-7-Salami | 3 ± 1 | +(18.4) | +(18.8) | – | – | +(18.5) | +(19.8) | +(18.1) | – | +(16.5) | – | – | – | – | ||||
| Blank-Salami | None | - * | - * | – | – | – | – | – | – | – | – | – | – | – | ||||
| D-6-Red fruits | Red fruits | TIAC 1873 | O55:H12 | stx1 | 56 ± 17 | +(19.3) | +(19.2) | – | – | – | – | +(23.0) | 18.8 | - * | – | - * | – | – |
| D-7-Red fruits | ± 7 | +(20.7) | +(20.7) | – | – | – | – | +(22.7) | 19.2 | – | – | – | – | – | ||||
| Blank-Red fruits | None | - * | - * | – | – | – | – | – | – | – | – | – | – | – | ||||
| D-6-minced meat | Minced meat | TIAC 1871 | O121:H19 | eae/stx2 | 64 ± 13 | +(15.4) | +(15.3) | – | - * | +(17.9) | +(18.2) | +(18.7) | – | +(17.2) | – | – | – | – |
| D-7-minced meat | 4 ± 2 | +(14.8) | +(15.2) | – | – | +(24.5) | +(24.6) | +(25.5) | – | +(23.5) | – | – | – | – | ||||
| Blank minced meat | None | +(15.4) | +(14.9) | – | – | – | – | – | – | – | – | – | – | – | ||||
| D-6-Blank | None | TIAC 2096 | O157:H7 | eae/stx2 | 27 ± 15 | +(14.7) | +(14.8) | – | – | +(14.9) | +(14.9) | +(15.0) | – | +(13.4) | – | – | – | – |
| D-7-Blank | 3 ± 1 | +(14.9) | +(14.4) | -* | – | +(14.6) | +(16.0) | +(14.8) | – | +(13.4) | – | – | – | – | ||||
| Blank-blank | None | – | – | – | – | – | – | – | – | – | – | – | – | – | ||||
+ there is specific amplification (with the correct Tm value), − no amplification, −* weak signal probably due to low contamination level was observed, Cq > 32 and < LOD Cq value observed with Cq > LOD, na not applicable