Table 1.

Comparison of the sensitivities of PCR assays with dilutions of DNA or DNA prepared from diluted cultures or seeded blood

Dilution and origin of template for PCRDetection by the following method:
EtBr-stained agarose gelSouthern blot (cpm)ELISA (OD)
10−4
 DNAa +b 22,249c 2.901c
 Cultured +25,2262.762
 Seeded bloodd +NDe ND
10−5
 DNA+16,8912.798
 Culture+16,7482.802
 Seeded blood+2,2822.625
10−6
 DNA+7,7342.917
 Culture+8,8022.621
 Seeded blood+1,9362.739
10−7
 DNA+1,0392.596
 Culture+1,8352.411
 Seeded blood+3421.294
10−8
 DNA1520.944
 Culture440.304
 Seeded blood1250.655
10−9
 DNA110.112
 Culture50.105
 Seeded blood110.106
Negative control
 DNA0.30.115
 Culture20.118
 Seeded blood30.120
  • a One milliliter of an overnight C. albicans culture was diluted to 10−1. The DNA was extracted as described in Materials and Methods and was then serially diluted to 10−9. The 10−1 DNA solution contained 2 μg of DNA per ml, as estimated by comparison with a marker on an EtBr-stained gel.

  • b A visible band (+) or no visible band (−) on agarose gel electrophoresis with EtBr staining.

  • c The background (Southern blot) and blank values (ELISA) were not deduced from the displayed values. The sensitivity of the assay in this experiment, as indicated by the calculated DNA or cell content of the 10−8 dilutions, was 200 fg of DNA per ml, 1 cell/ml (culture dilution), and 4 cells/ml (seeded blood).

  • d Tenfold serial dilutions of the C. albicans culture diluted 10−1 in water or blood were obtained as explained in Materials and Methods. Quantification of cell numbers in the 10−1 was obtained by measuring theA 540 of the cultures, and the quantities were 1.2 × 10−7 and 3.75 × 10−7cells/ml, respectively. A 10-μl aliquot of each dilution was used for PCR amplification. A 10-μl aliquot of the PCR product was used for detection by agarose gel detection electrophoresis with EtBr staining, Southern blotting, or ELISA.

  • e ND, not determined.