Sensitivity of polymerase chain reaction for detection of known aliquots of Trypanosoma cruzi in the blood of mice: an in vitro study

RESUMO

To evaluate the sensitivity of polymerase chain reaction (PCR) to reveal known number of trypomastigote in the blood of mice, three separate experiments were done. First To eight samples of 500mul of normal mice blood, one aliquot of 1, 2, 3, 4, 5, 10, and 50 trypomastigotes respectively, were added. Second and third 10 aliquots with 1 and 10 with 2 trypomastigotes were added to samples of 500mul of normal mice blood. Positive control 500mul of blood containing 100,000 trypomastigotes. For kDNA minicircles amplification by PCR the primersS35 and S36 were used. PCR revealed products of 330 b.p in the positive controls. When only one sample with the aliquots of 1 or 2 trypomastigotes was examined, results were negative; results were positive with aliquots of 3 to 50 trypomastigotes. In the 2nd and 3rd experiments, 9/10 aliquots with one parasite and 9/10 with 2 trypomastigotes were positive revealing a high sensitivity of this reaction. In conclusion, the presence of one single parasite in 500mul of blood, is enough for a positive PCR. This method could be used as a complement to the various parasitological cure tests in treated mice, when low volumes of blood are individually examined