title: Real-Time PCR in faecal samples of Triatoma infestans obtained by xenodiagnosis: proposal for an exogenous internal control.
abstract: BACKGROUND
  The polymerase chain reaction (PCR) has proved to be a sensitive technique to detect Trypanosoma cruzi in the chronic phase of Chagas disease, which is characterized by low and fluctuating parasitemia. Another technique proposed for parasitological diagnosis in this phase of infection combines a microscopic search for motile trypomastigote forms in faecal samples (FS) obtained by xenodiagnosis (XD) with conventional PCR (XD-PCR). In this study we evaluate the use of human blood DNA as an exogenous internal control (EIC) for real time PCR (qPCR) combined with XD (XD-qPCR) using chromosome 12 (X12) detection.
  
  
  RESULTS
  None of the FS-XD evaluated by qPCR amplified for X12. Nevertheless, all the EIC-FS-XD mixtures amplified for X12.
  
  
  CONCLUSIONS
  We determined that X12 is useful as an EIC for XD-qPCR because we showed that the FS-XD does not contain human DNA after 30 or more days of XD incubation. This information is relevant for research on T. cruzi by XD-qPCR since it allows ruling out inhibition and false negative results due to DNA loss during the process of extraction and purification.
authors.affiliation: Faculty of Medicine, Institute of Biomedical Sciences, University of Chile, Santiago, Chile.
authors.forename: Nicolás
authors.initials: N
authors.lastname: Bravo
authors.forename: Catalina
authors.initials: C
authors.lastname: Muñoz
authors.forename: Nicolás
authors.initials: N
authors.lastname: Nazal
authors.forename: Miguel
authors.initials: M
authors.lastname: Saavedra
authors.forename: Gabriela
authors.initials: G
authors.lastname: Martínez
authors.forename: Eduardo
authors.initials: E
authors.lastname: Araya
authors.forename: Werner
authors.initials: W
authors.lastname: Apt
authors.forename: Inés
authors.initials: I
authors.lastname: Zulantay
mesh_terms: D000818:Animals; D001769:Blood; D002881:Chromosomes, Human, Pair 12; D006801:Humans; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods* / Q000592:standards*; D012015:Reference Standards; D014224:Triatoma / Q000469:parasitology*; D014349:Trypanosoma cruzi / Q000302:isolation & purification*; D020525:Xenodiagnosis / Q000379:methods*