title: Brazilian spotted fever: real-time PCR for diagnosis of fatal cases.
abstract: Suspicion of Brazilian spotted fever (BSF) should occur in endemic regions upon surveillance of the acute febrile icteric hemorrhagic syndrome (AFIHS). However, limitations associated with currently available laboratory tests pose a challenge to early diagnosis, especially in fatal cases. Two real-time PCR (qPCR) protocols were evaluated to diagnose BSF in 110 fatal AFIHS cases, collected in BSF-endemic regions in 2009-2010. Of these, 24 were positive and 86 negative by indirect immunofluorescence (IFA) assay (cut-off IgG and/or IgM ≥ 128). DNA from these samples was used in the qPCR protocols: one to detect Rickettsia spp. (citrate synthase gene) and another to determine spotted fever group (SFG) Rickettsia species (OmpA gene). Of the 24 IFA-positive samples, 5 (21%) were positive for OmpA and 9 (38%) for citrate synthase. In the IFA-negative group (n=86), OmpA and citrate synthase were positive in 23 (27%) and 27 (31%), respectively. These results showed that the 2 qPCR protocols were about twice as sensitive as the IFA test alone (93% concordance). In conclusion, qPCR is a sensitive method for the diagnosis of fatal BSF cases and should be considered for routine surveillance of AFIHS in places like Brazil, where spotted fever-related lethality is high and other endemic diseases like dengue and leptospirosis can mislead diagnosis.
authors.affiliation: Adolfo Lutz Institute, Secretary of State for Health, Sao Paulo, Brazil. fcpereir@usp.br
authors.forename: Fabiana Cristina Pereira
authors.initials: FC
authors.lastname: dos Santos
authors.forename: Elvira Maria Mendes
authors.initials: EM
authors.lastname: do Nascimento
authors.forename: Gizelda
authors.initials: G
authors.lastname: Katz
authors.forename: Rodrigo Nogueira
authors.initials: RN
authors.lastname: Angerami
authors.forename: Silvia
authors.initials: S
authors.lastname: Colombo
authors.forename: Eliana Rodrigues
authors.initials: ER
authors.lastname: de Souza
authors.forename: Marcelo Bahia
authors.initials: MB
authors.lastname: Labruna
authors.forename: Marcos Vinicius
authors.initials: MV
authors.lastname: da Silva
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001938:Brazil; D002950:Citrate (si)-Synthase / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D057089:Pathology, Molecular / Q000379:methods*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012281:Rickettsia / Q000235:genetics / Q000302:isolation & purification*; D012373:Rocky Mountain Spotted Fever / Q000175:diagnosis*; D012680:Sensitivity and Specificity
chemical_list: D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; C078167:OMPA outer membrane proteins; D002950:Citrate (si)-Synthase