. 2000 May;66(5):1769–1776. doi: 10.1128/aem.66.5.1769-1776.2000

TABLE 3.

Recovery and detection of serovar Enteritidis and L. monocytogenes in 1-ml samples of whole milk or ice cream after bacterial immobilization with zirconium hydroxide and subsequent RT-PCR

Organism	Whole milk				Ice cream
	Inoculum^a (CFU/ml)	Avg % recovery^b		Detection (PCR/confirm)^c	Inoculum^a (CFU/ml)	Avg % recovery^b		Detection (PCR/confirm)^c
	Inoculum^a (CFU/ml)	2^o concn	Ppt	Detection (PCR/confirm)^c	Inoculum^a (CFU/ml)	2^o concn	Ppt	Detection (PCR/confirm)^c
L. monocytogenes	10⁴	96 ± 1^x	114 ± 5^x	3/3	10⁴	91 ± 1^x	104 ± 23^y	3/3
	10³	92 ± 1^y	122 ± 12^x	3/3	10³	67 ± 1^y	78 ± 7^y	3/3
	10²	92 ± 1^y	100 ± 8^x	3/3	10²	61 ± 3^y	71 ± 7^y	3/3
	10¹	95 ± 4^x	93 ± 20^x	0/3	10¹	84 ± 13^x	161 ± 11^x	2/3
Serovar Enteritidis	10⁴	97 ± 2^x	83 ± 7^x	3/3	10⁴	95 ± 1^x	69 ± 8^x	3/3
	10³	96 ± 1^x	90 ± 19^x^y	3/3	10³	89 ± 1^y	65 ± 2^x	3/3
	10²	97 ± 2^x	77 ± 11^x	3/3	10²	87 ± 1^z	64 ± 4^x	1/3
	10¹	96 ± 5^x	107 ± 1^y	0/3	10¹	71 ± 14^w	79 ± 14^x	2/3

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

Average percent recovery (mean ± standard deviation) of three replicate samples; for 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 immobilization {i.e., after 1^o and 2^o concentration} × 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 (w, 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 supernatant versus direct plating of the immobilized pellet were compared.

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