title: Pneumococcal DNA is not detectable in the blood of healthy carrier children by real-time PCR targeting the lytA gene.
abstract: The diagnosis of invasive pneumococcal disease (IPD) is currently based on culture methods, which lack sensitivity, especially after antibiotic therapy. Molecular methods have improved sensitivity and do not require viable bacteria; however, their use is complicated by reports of low specificity with some assays. The present study investigated the specificity of a real-time PCR targeting lytA for the detection of IPD. A group of 147 healthy children, aged 6 months to 16 years (mean 6.4 years, median 4.9 years, interquartile range 6.4 years), who were in hospital for routine examinations, were tested for pneumococcal carrier status and for the presence of detectable pneumococcal DNA in their blood by real-time PCR targeting the pneumococcal lytA gene. In addition, 35 culture-positive biological samples were analysed. Urine was examined for the presence of pneumococcal DNA and C-polysaccharide antigen. Carriage was detected in 77 of the 147 subjects (52.4 %); however, regardless of carrier status, none of the subjects had a positive result from blood. Analysis of the culture-positive biological samples yielded positive results in 100 % (15/15) of cerebrospinal fluid samples and 95 % (19/20) of blood samples. All urine samples from healthy carriers were negative for DNA, whilst antigenuria was detected in 44/77 carriers (57.1 %). In conclusion, real-time PCR is both sensitive and specific and can be a useful tool in the routine diagnosis of IPD. Its sensitivity, which surpasses that of other methods for this purpose, does not come at the cost of reduced specificity.
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Azzari
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Cortimiglia
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Moriondo
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Clementina
authors.initials: C
authors.lastname: Canessa
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Lippi
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Ghiori
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Becciolini
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: de Martino
authors.affiliation: Department of Paediatrics, Anna Meyer Children's University Hospital, Florence, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Resti
mesh_terms: D000293:Adolescent; D001431:Bacteriological Techniques / Q000379:methods*; D001769:Blood / Q000382:microbiology; D002353:Carrier State / Q000175:diagnosis* / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000097:blood* / Q000652:urine; D006801:Humans; D007223:Infant; D009297:Nasal Mucosa / Q000382:microbiology; D011008:Pneumococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D014556:Urine / Q000382:microbiology
chemical_list: D004269:DNA, Bacterial