TABLE 2.

Recovery and detection of serovar Enteritidis and L. monocytogenes in 25-ml reconstituted NFDM samples after bacterial immobilization with zirconium hydroxide and subsequent RT-PCR

Inoculuma (CFU/25 ml)	Serovar Enteritidis				L. monocytogenes
	Avg % recoveryb			Detection (PCR/LCR)c	Avg % recoveryb			Detection (PCR/Hyb)c
	1o concn	2o concn	Ppt		1o concn	2o concn	Ppt
104	97 ± 2x	96 ± 3xy	69 ± 4z	3/3	98 ± 4x	98 ± 1x	96 ± 1x	3/3
103	85 ± 3y	95 ± 3yz	85 ± 3y	3/3	96 ± 1x	96 ± 1x	92 ± 1y	3/3
102	98 ± 2x	96 ± 1xy	95 ± 1x	3/3	89 ± 2y	97 ± 2x	89 ± 9xy	3/3
101	94 ± 6xy	51 ± 41z	65 ± 16yz	1/3	78 ± 10y	95 ± 5x	78 ± 12y	2/3

^aTotal CFU at input is taken as 100%; input level confirmed by plating samples before bacterial concentration. 

^bAverage percent recovery (mean ± standard deviation) of three replicate samples; for primary concentration (1^o concn) and secondary concentration (2^o concn), percent recovery was calculated as previously reported (8): [percent recovery = (total population in sample before concentration − total population in supernatant after 1^o concentration or after 2^o concentration {i.e., immobilization}) × 100/(total population in sample before concentration)]. For the immobilized pellet (Ppt), percent recovery was calculated as follows: [percent recovery = (total population in pellet after immobilization {i.e., after 1^o and 2^o concentrations} × 100/(total population in sample before concentration)]. Different superscript letters (x, y, and z) identify statistically significant differences (P ≤ 0.05) in percent recovery at different input levels of each organism. Boldface data identify statistically significant differences (P ≤ 0.05) between percent recovery values when calculations based on loss to the supernatant versus direct plating of the immobilized pellet were compared. 

^cDetection was done by agarose gel electrophoresis of PCR products and subsequent confirmation by DNA hybridization (PCR/Hyb for L. monocytogenes) or LCR (PCR/LCR for serovar Enteritidis).