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Failure to detect capsule gene bexA in Haemophilus influenzae types e and f by real-time PCR due to sequence
1Health Protection Agency London, Department of Virology, King's College Hospital (Dulwich site), Dulwich Hospital, East Dulwich Grove, London SE22 8QF, UK.
Abstract:
Detection of the conserved capsule gene bexA is used to distinguish capsulate from non-capsulate Haemophilus influenzae. While developing a real-time PCR assay to detect bexA, it was found that bexA probes produced a detectable signal for H. influenzae types a to d, but failed to do so for H. influenzae types e and f. Sequencing revealed differences compared with H. influenzae types a to d within probe binding sites. To prevent misclassification of strains as non-capsulate, assays must detect all capsular types.