TABLE 3.

Detection of PCR-inhibitory activity in different food matrices using the L. monocytogenes hly-IAC Q-PCR assay^a

L. monocytogenes contamination (CFU/g)	CFU/reaction	Results for:
		Fermented pork sausage			Frankfurter sausage			Cooked ham			Raw pork meat			Raw salmon			Smoked salmon
		hlye		IAC	hlyf		IAC	hlyg		IAC	hlyh		IAC	hlyh		IAC	hlyh		IAC
		CT valuesb	Relative accuracyc	CT valuesd	CT values	Relative accuracy	CT values	CT values	Relative accuracy	CT values	CT values	Relative accuracy	CT values	CT values	Relative accuracy	CT values	CT values	Relative accuracy	CT values
3 × 107	3 × 103	26.05 ± 0.30	94.34	33.75 ± 0.71	25.94 ± 0.23	103.98	33.42 ± 0.35	26.05 ± 0.30	105.64	33.45 ± 0.64	ND	NA	ND	ND	NA	ND	ND	NA	ND
3 × 106	3 × 102	29.26 ± 0.31	113.15	33.52 ± 0.45	29.68 ± 0.37	93.06	33.69 ± 0.54	29.43 ± 0.17	90.19	33.62 ± 0.69	ND	NA	ND	ND	NA	ND	ND	NA	ND
3 × 105	3 × 101	33.01 ± 0.62	94.98	33.65 ± 0.54	29.43 ± 0.59	104.67	33.55 ± 0.75	32.49 ± 0.57	106.33	33.81 ± 0.45	ND	NA	ND	ND	NA	ND	ND	NA	ND

^aNA, not applicable; ND, amplification not detected.

^bFAM C_T values (mean plus or minus standard deviation) were calculated with a prefixed threshold at 0.035, and a baseline from cycles 3 to 15.

^cDegree of correspondence between the response obtained by the reference method (2) and the response obtained by the alternative (Q-PCR) method. Note that in those samples where there was PCR inhibition as detected by the absence of IAC signal the relative accuracy values dropped dramatically.

^dVIC C_T values (mean plus or minus standard deviation) were calculated with a prefixed threshold at 0.035, and a baseline from cycles 3 to 15.

^eEfficiency, 0.94; linearity, 0.9981.

^fEfficiency, 0.93; linearity, 0.9983.

^gEfficiency, 1.04; linearity, 0.9991.

^hEfficiency, not applicable; linearity, not applicable.