title: Quantitative detection of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in lower respiratory tract samples by real-time PCR.
abstract: The limitation of polymerase chain reaction (PCR) in diagnosis of lower respiratory tract infections (LRTIs) caused by Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis has been a distinguishing colonization from infection. We assess here the usefulness of real-time quantitative PCR (RQ-PCR) performed on lower respiratory tract samples to overcome this problem. Consecutive respiratory tract samples from patients with and without signs of infection (n = 203) were subjected to RQ-PCR, targeting the genes pneumolysin (S. pneumoniae), fumarate reductase (H. influenzae), and outer membrane protein B (M . catarrhalis). DNA from positive controls with predefined colony forming units (CFUs) per milliliter were included to allow estimation of CFU per milliliter for the test samples. In parallel, assessment of quantitative cultures from all samples was performed. In the group of patients with LRTI, significant pathogens (>/=10(5) CFU/mL) were found in 32/135 samples (23.7%) with culture, in 51/135 (37.7%) with RQ-PCR, and in 59/135 (43.7%) when combining the methods.
authors.affiliation: Clinical Microbiology, Microbiology and Tumor Biology Center, Karolinska Institutet, Karolinska University Hospital Solna, SE-17176 Stockholm, Sweden.
authors.forename: Madeleine
authors.initials: M
authors.lastname: Kais
authors.forename: Carl
authors.initials: C
authors.lastname: Spindler
authors.forename: Mats
authors.initials: M
authors.lastname: Kalin
authors.forename: Ake
authors.initials: A
authors.lastname: Ortqvist
authors.forename: Christian G
authors.initials: CG
authors.lastname: Giske
mesh_terms: D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D017714:Community-Acquired Infections / Q000175:diagnosis / Q000382:microbiology; D006193:Haemophilus influenzae / Q000302:isolation & purification*; D006801:Humans; D001936:Moraxella catarrhalis / Q000302:isolation & purification*; D045828:Moraxellaceae Infections / Q000175:diagnosis; D011008:Pneumococcal Infections / Q000175:diagnosis; D018410:Pneumonia, Bacterial / Q000175:diagnosis / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000302:isolation & purification*