Quantitative detection of Moraxella catarrhalis in nasopharyngeal secretions by real-time PCR

Philip Day, Oliver Greiner, Philip J R Day, Martin Altwegg, David Nadal

    Research output: Contribution to journalArticlepeer-review


    The recognition of Moraxella catarrhalis as an important cause of respiratory tract infections has been protracted, mainly because it is a frequent commensal organism of the upper respiratory tract and the diagnostic sensitivity of blood or pleural fluid culture is low. Given that the amount of M. catarrhalis bacteria in the upper respiratory tract may change during infection, quantification of these bacteria in nasopharyngeal secretions (NPSs) by real-time PCR may offer a suitable diagnostic approach. Using primers and a fluorescent probe specific for the copB outer membrane protein gene, we detected DNA from serial dilutions of M. catarrhalis cells corresponding to 1 to 106 cells. Importantly, there was no difference in the amplification efficiency when the same DNA was mixed with DNA from NPSs devoid of M. catarrhalis. The specificity of the reaction was further confirmed by the lack of amplification of DNAs from other Moraxella species, nontypeable Haemophilus influenzae, H. influenzae type b, Streptococcus pneumoniae, Streptococcus oralis, Streptococcus pyogenes, Bordetella pertussis, Corynebacterium diphtheriae, and various Neisseria species. The assay applied to NPSs from 184 patients with respiratory tract infections performed with a sensitivity of 100% and a specificity of up to 98% compared to the culture results. The numbers of M. catarrhalis organisms detected by real-time PCR correlated with the numbers detected by semiquantitative culture. This real-time PCR assay targeting the copB outer membrane protein gene provided a sensitive and reliable means for the rapid detection and quantification of M. catarrhalis in NPSs; may serve asa as a tool to study changes in the amounts of M. catarrhalis during lower respiratory tract infections or following vaccination against S. pneumoniae, H. influenzae, or N. meningitidis; and may be applied to other clinical samples.
    Original languageEnglish
    Pages (from-to)1386-1390
    Number of pages4
    JournalJournal of clinical microbiology
    Issue number4
    Publication statusPublished - 1 Apr 2003


    • analysis
    • Bacterial Outer Membrane Proteins
    • blood
    • Child
    • Child,Preschool
    • Comparative Study
    • Culture Media
    • diagnosis
    • Disease
    • Dna
    • DNA,Bacterial
    • Evaluation Studies
    • genetics
    • Gram-Negative Bacterial Infections
    • Human
    • isolation & purification
    • Membrane Proteins
    • methods
    • microbiology
    • Moraxella (Branhamella) catarrhalis
    • Nasopharynx
    • Polymerase Chain Reaction
    • Proteins
    • Respiratory Tract Infections
    • secretion
    • Sensitivity and Specificity
    • Support,Non-U.S.Gov't
    • Vaccination


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