Table 2.
Performance of TAC and qPCR on spiked samples in sample matrices varying in levels of PCR inhibitors
|
Sensitivity |
Accuracy |
|||
|---|---|---|---|---|
| TAC | qPCR | TAC | qPCR | |
| Sample matrix | ||||
| Nuclease-free water | 92% (59/64) | 100% (64/64) | 91% (73/80) | 99% (79/80) |
| Creek water | 93% (28/30) | 97% (29/30) | 80% (16/20) | 80% (16/20) |
| Sediment | 60% (18/30) | 57% (17/30) | 43% (17/40) | 30% (12/40) |
| Human stool | 83% (25/30) | 97% (29/30) | 80% (24/30) | 90% (27/30) |
| Fluorinated potable water | 71% (40/56) | 95% (53/56) | 63% (35/56) | 73% (41/56) |
| Extraction blank | 83% (25/30) | 97% (29/30) | 80% (32/40) | 83% (33/40) |
| Target | ||||
| Bacteroides | 85% (23/27) | 85% (23/27) | 82% (22/27) | 85% (23/27) |
| Campylobacter jejuni, C coli | 77% (24/31) | 87% (27/31) | 49% (18/37) | 78% (29/37) |
| Cryptosporidium | 77% (24/31) | 90% (28/31) | 70% (26/37) | 54% (20/37) |
| EPEC (eae) | 74% (23/31) | 90% (28/31) | 73% (27/37) | 78% (29/37) |
| Giardia | 90% (28/31) | 97% (30/31) | 82% (22/27) | 82% (22/27) |
| Salmonella | 84% (26/31) | 97% (30/31) | 78% (25/32) | 69% (22/32) |
| STEC (stx1) | 85% (23/27) | 96% (26/27) | 88% (28/32) | 91% (29/32) |
| STEC (stx2) | 77% (24/31) | 94% (29/31) | 78% (29/37) | 92% (34/37) |
Data are % (n/N). Results are shown by sample matrix and by target. Sensitivity is defined as the percentage of spiked targets that were detected. Accuracy is measured as percentage of assays within one log10 of the spiked concentration; assays where background levels of pathogen were detected by qPCR or TAC are excluded from these calculations (20 creek water assays and ten human stool assays excluded). TAC=TaqMan array card. STEC=Shiga toxin-producing Escherichia coli. EPEC=enteropathogenic Escherichia coli.