The prevalence of atypical community-acquired infections as acute pulm
onary exacerbations in patients with cystic fibrosis was prospectively
studied, Thirty-two patients admitted to the hospital because of acut
e pulmonary exacerbations and 24 clinically stable patients seen for t
heir routine visits were examined, The prevalence of infection with Ch
lamydia pneumoniae was assessed by culture and serology, and the prese
nce of IgE to C. pneumoniae was studied by immunoblotting, A subgroup
of patients was also examined for the presence of Mycoplasma pneumonia
e infection, C. pneumoniae was isolated from four patients presenting
with acute pulmonary exacerbations (12.5%) and from none of the stable
patients; all patients for whom cultures were positive also had IgE t
o C. pneumoniae, Polymerase chain reaction analysis for M. pneumoniae
was not positive for any patient, and only one patient with an acute e
xacerbation had an antibody titer compatible with a recent infection,
We conclude that infection with C. pneumoniae is associated with acute
pulmonary exacerbations in some patients with cystic fibrosis and tha
t it may trigger the production of IgE specific to C. pneumoniae, thus
leading to bronchial reactivity in these patients.