Braz, Lucia Maria de Almeida

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Cadernos Espinosanos (E-Journal)

Rev. Inst. Med. trop. S. Paulo49(1):40, January-February, 2007*This thesis is available at the Library of the Instituto de Medicina Tropical de São PauloSUMMARY OF THESIS*BRAZ, Lúcia Maria de Almeida - Comparação da Reação em Cadeia da Polimerase com o exame microscópico na detecção do Trypanosomacruzi em amostras procedentes do trato digestório do Triatoma infestans.  São Paulo, 2006. (Tese de doutoramento - Faculdade deMedicina da Universidade de São Paulo.COMPARISON OF POLYMERASE CHAIN REACTION WITH MICROSCOPIC EXAMINATION TO DETECTTrypanosoma cruzi IN Triatoma infestans DIGESTIVE TRACT SAMPLESImmunosuppressed patients may experience episodes of Chagasdisease reactivation with negative direct parasitological investigation.In this situation xenodiagnosis is recommended, even though thistechnique depends very much on the biologist’s background to detectT. cruzi under microscopic examination and demands 30 to 60 days.Polymerase Chain Reaction (PCR) has been used to increase sensitivityof xenodiagnosis. The present study has aimed at comparing detectionof T.cruzi in T. infestans digestive tract samples by PCR and microscopicexamination (ME) performed in the context of xenodiagnosis, atdifferent times after bugs feeding in Balb/C mice experimentallyinfected by T.cruzi, and divided in two groups: with high parasitemiaand with low parasitemia. Representing the first group, 110 triatomineswere divided in 11 groups of 10 triatomines each, and fed in Balb/Cmice presenting with high parasitemia of T.cruzi. As controls, 110triatomines were divided in 11 groups of 10 insects each, and were fedin non infected mice. The second group was composed of 220triatomines divided in 11 groups of 20 triatomines each and fed inmice presenting low parasitemia of T.cruzi. As controls, 55 triatomineswere divided in 11 groups of five insects each, and were fed in noninfected mice. Samples of all triatomines of each group were examinedon the 1st,  2nd, 3rd, 4th, 5th, 10th, 15th, 20th, 25th, 30th and 60th day afterfeeding. Samples were separated in two aliquots: the first one wasexamined by ME and the second one by PCR. Amplifications wereperformed with a new pair of primers from the genomic TCZ sequenceof T.cruzi. Results showed that all samples from control triatomineswere negative by both methods. On the 1st, 2nd, 3rd, 4th, 5th,10th, 15th,20th, 25th, 30th and 60th day, of the high parasitemia model, results were:75%, 60%, 50%, 40%, 60%, 90%, 100%, 88.9%, 88.9%, 100% and90% of positivity by PCR; and 50%, 30%, 30%, 40%, 30%, 60%,50%, 55.6%, 33.3%, 70% and 20% by ME, respectively. In the lowparasitemia model, on the 1st day, only PCR was positive in 40% ofcases and on the 2nd, 3rd, 4th, 5th, 10th, 15th, 20th, 25th, 30th and 60th day,PCR presented positivity of 55%, 40%, 70%, 63%, 60%, 65%, 52.6%,60%, 78.9% and 68.4%; and by ME 5%, 5%, 15%, 15.8%, 25%, 25%,31.6%, 30%, 36.8% and 36.8%, respectively. The statistical analysismade by means of the McNemar procedure showed discordances amongresults obtained by PCR and ME. This difference was statisticallysignificant (p < 0.05), thus indicating superiority of PCR with respectto ME. We concluded that the PCR technique presented with advantagesto Chagas disease diagnosis when compared to ME, as a complementarytest of xenodiagnosis, in 10 of 11 times in the high parasitemia model,and in all study times in the low parasitemia model. Considering thatthe low parasitemia model resembles the situation found inimmunosuppressed patients with reactivation of Chagas disease, thisfinding is of clinical relevance as it may influence medical decisionsand the prognosis of those patients.Lucia Maria de Almeida Brazlmabraz@usp.br

Comparison of polymerase chain reaction with microscopic examination to detect Trypanosoma cruzi in Triatoma infestans digestive tract samples

https://www.revistas.usp.br/rimtsp/article/download/31061/32945

Comparação da Reação em Cadeia da Polimerase com o exame microscópico na detecção do Trypanosoma cruzi em amostras procedentes do trato digestório do Triatoma infestans

Comparação da Reação em Cadeia da Polimerase com o exame microscópico na detecção do Trypanosoma cruzi em amostras procedentes do trato digestório do Triatoma infestans

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Cadernos Espinosanos (E-Journal)