TABLE 3.

Comparison of L. pneumophila counts in natural waters obtained by culture and by the ChemScanRDI

SampleCulture resultNo. of validated bacteria/liter (CV) by ChemScanRDIRatio of ChemScan counts to culture counts
CFU/liter (CV)aIdentificationTotal L. pneumophilaL. pneumophila sg 1L. pneumophila sg 2-6, 8-10, 12-15
11.2 × 102 (24.7) L. pneumophila sg 13.9 × 104 (2.1)2.5 × 104 (1.2)1.4 × 104 (4.8)325
21.1 × 104 (11.4) L. pneumophila sg 2-141.2 × 105 (6.2)1.1 × 104 (3.9)1.1 × 104 (30.1)10.9
35.4 × 103 (7.2)b L. pneumophila sg 17.4 × 103 (9.5)3 × 103 (2.7)4.4 × 103 (1.2)1.4
41.2 × 102 (24.7) L. pneumophila sg 2-142.3 × 103 (9.4)02.3 × 103 (9.4)19.2
51.3 × 102 (11.2) L. pneumophila sg 2-142.8 × 103 (11.2)02.8 × 103 (11.2)21.5
62.5 × 102 (34.6) L. pneumophila sg 2-143.7 × 104 (2.6)03.7 × 10 (3.0)148
704.1 × 106 (0.9)c1.7 × 103 (9.6)4.1 × 106 (0.9)
81.4 × 103 L. pneumophila sg 19.7 × 1038.2 × 1031.5 × 1036.9
93.4 × 103 L. pneumophila sg 17.9 × 1037.6 × 1032.7 × 1022.3
1002.2 × 1032.1 × 1031.3 × 102
1101.9 × 1031.9 × 1030
125.9 × 103 L. pneumophila sg 13.2 × 1032.7 × 1035 × 1020.5
131.5 × 103 L. pneumophila sg 1 (8/10)d9 × 1038.8 × 1032 × 1026
L. pneumophila sg 5 (2/10)
140000
150000
160000
170000
180000
190000
200000
211.4 × 103 L. pneumophila sg 15.1 × 1035 × 103503.6
222.6 × 103 L. pneumophila sg 11054.4 × 10310538
233.6 × 103 L. pneumophila sg 15.1 × 1035 × 103501.4
246 × 102 L. anisa (1/10)1.4 × 1031.3 × 1031.5 × 1022.3
L. pneumophila sg 1 (6/10)
L. pneumophila sg 5 (3/10)
254 × 102 L. anisa (1/5)2.9 × 1032.7 × 1031.5 × 1027.3
L. pneumophila sg 1 (4/5)
266 × 102 L. pneumophila sg 1 (1/6)1.9 × 1031.8 × 1031023.2
L. pneumophila sg 5 (5/6)
  • a CV, coefficient of variation.

  • b Mean of two values: 5.1 × 103 and 5.7 × 103 CFU/L. The deviant value 4 × 104 came from a sample more contaminated than the other two replicates.

  • c Direct counts were confirmed in another culture-negative sample.

  • d Identification of 5 or 10 colonies.