Table 2.

Spore recovery from a stainless steel surface^a using a sponge wipe sampling and processing protocol

Type and target inoculum level (log10)	Reference CFUb			Recovered CFU			%Rc
	No. of plates	Mean	%CV	No. of samples	Mean	Mean	SE	CVBd	CVWe	CVTf
Sampled wipes (sampled and processed)
1	28	26.1	52	63	8.4	32.4	4.4	31.3	69.3	76.1
2	30	536	25	63	132.6	24.4	2.8	31.3	35.0	47.0
4	15	33,140	20	56g	9,984.0	30.1	2.3	19.9	19.5	27.9
Positive-control wipes (processed only)
1	28	8.7	52	17h	4.1	46.1	9.6	47.7	54.0	72.0
2	30	179	25	18	112.7	66.5	7.3	29.5	20.3	35.8
4	15	11,047	20	16g	8,607.0	77.9	4.5	14.4	10.6	17.8

^aMeasuring 25.4 by 25.4 cm (645.16 cm²).

^bReference CFU count estimated by replicate spread plate and culture of inoculating suspension. Three milliliters applied to stainless steel surface and 1 ml applied to positive-control wipes.

^cMean, SE, and between- and within-lab variances of %R were estimated using a random-effect regression model to account for the correlated nature of the data.

^d%CV_B, between-lab coefficient of variation defined as 100% times the square root of the estimated between-lab variance divided by the mean %R.

^e%CV_W, within-lab coefficient of variation defined as 100% times the square root of the estimated within-lab variance divided by the mean %R.

^f%CV_T, the total coefficient of variation, was estimated as 100% times the square root of the total variance (incorporating between- and within-lab variances) divided by the mean %R.

^gThe number is lower for the 10⁴ inoculum because one laboratory's quantitative data were omitted due to procedural error.

^hResults exclude a single sample that was deemed to be an outlier.