Development and evaluation of a sensitive PCR-ELISA system for detection of schistosoma infection in feces.
BACKGROUND
A PCR-enzyme-linked immunosorbent assay (PCR-ELISA) was developed to overcome the need for sensitive techniques for the efficient diagnosis of Schistosoma infection in endemic settings with low parasitic burden.


RESULTS
This system amplifies a 121-base pair tandem repeat DNA sequence, immobilizes the resultant 5' biotinylated product on streptavidin-coated strip-well microplates and uses anti-fluorescein antibodies conjugated to horseradish peroxidase to detect the hybridized fluorescein-labeled oligonucleotide probe. The detection limit of the Schistosoma PCR-ELISA system was determined to be 1.3 fg of S. mansoni genomic DNA (less than the amount found in a single cell) and estimated to be 0.15 S. mansoni eggs per gram of feces (fractions of an egg). The system showed good precision and genus specificity since the DNA target was found in seven Schistosoma DNA samples: S. mansoni, S. haematobium, S. bovis, S. intercalatum, S. japonicum, S. magrebowiei and S. rhodaini. By evaluating 206 patients living in an endemic area in Brazil, the prevalence of S. mansoni infection was determined to be 18% by examining 12 Kato-Katz slides (41.7 mg/smear, 500 mg total) of a single fecal sample from each person, while the Schistosoma PCR-ELISA identified a 30% rate of infection using 500-mg of the same fecal sample. When considering the Kato-Katz method as the reference test, artificial sensitivity and specificity rates of the PCR-ELISA system were 97.4% and 85.1%, respectively. The potential for estimating parasitic load by DNA detection in feces was assessed by comparing absorbance values and eggs per gram of feces, with a Spearman correlation coefficient of 0.700 (P<0.0001).


CONCLUSIONS
This study reports the development and field evaluation of a sensitive Schistosoma PCR-ELISA, a system that may serve as an alternative for diagnosing Schistosoma infection.
Gomes
Luciana Inácia
LI
Laboratório de Pesquisas Clínicas, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz (Fiocruz), Belo Horizonte, Minas Gerais, Brazil.
Dos Santos Marques
Letícia Helena
LH
Enk
Martin Johannes
MJ
de Oliveira
Maria Cláudia
MC
Coelho
Paulo Marcos Zech
PM
Rabello
Ana
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005243:Feces / Q000469:parasitology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D051379:Mice; D008875:Middle Aged; D016133:Polymerase Chain Reaction / Q000379:methods*; D015995:Prevalence; D012547:Schistosoma / Q000235:genetics / Q000302:isolation & purification*; D012552:Schistosomiasis / Q000175:diagnosis* / Q000453:epidemiology* / Q000469:parasitology; D012680:Sensitivity and Specificity; D055815:Young Adult