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September 9, 1996

Roentgenographic Findings of Pneumonia Caused by Chlamydia pneumoniae: A Comparison With Streptococcus Pneumonia

Author Affiliations

From the National Public Health Institute, Oulu, Finland (Dr Kauppinen); and the Clinical Microbiology Laboratory (Dr Kauppinen), the Department of Diagnostic Radiology (Drs Lähde and Syrjälä), and the Departments of Hospital Infection Control and Internal Medicine (Dr Syrjälä), Oulu University Hospital.

Arch Intern Med. 1996;156(16):1851-1856. doi:10.1001/archinte.1996.00440150107012

Background:  Pneumonia caused by Chlamydia pneumoniae or Streptococcus pneumoniae cannot be reliably differentiated by clinical signs or symptoms.

Objective:  To find differences in the roentgenographic patterns of community-acquired pneumonia caused by C pneumoniae, S pneumoniae, or both in hospitalized patients during a C pneumoniae epidemic in Finland.

Methods:  The patients were divided into 3 groups: 24 patients with serologic evidence of C pneumoniae only; 8 patients with combined C pneumoniae and S pneumoniae infection; and 13 patients with infection caused by S pneumoniae only. The chest roentgenograms obtained on admission to the hospital, during the hospital stay, and at follow-up visits were reevaluated by one of us (S.L.) who was unaware of the causative organism. In the final study groups, other causes of community-acquired pneumonia were excluded by a large pattern of microbiological methods.

Results:  Bronchopneumonia was observed in 21 (88%) of the group with C pneumoniae and 10 (77%) of the group with S pneumoniae (P=.67). Lobar or sublobar (air space) pneumonia was seen in 7 (29%) of the patients with C pneumoniae compared with 7 (54%) with pneumonia caused by S pneumoniae. In the combined group, bronchopneumonia was seen as frequently as in the group with C pneumoniae, and air-space involvement was seen as frequently as in the group with S pneumoniae. The pneumonic shadowing was usually unilateral and in the lower lobes in all groups. Of the patients in the C pneumoniae group, 17% had residual abnormalities at follow-up visits.

Conclusions:  Roentgenographic changes cannot be used to differentiate pneumonia caused by C pneumoniae from that caused by S pneumoniae. Thus, initial antibiotic treatment should be directed at the pathogens that commonly cause community-acquired pneumonia.Arch Intern Med. 1996;156:1851-1856

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