Related Experiment Video
Updated: Mar 24, 2026
Following in Real Time the Impact of Pneumococcal Virulence Factors in an Acute Mouse Pneumonia Model Using Bioluminescent Bacteria
Published on: February 23, 2014
Chlamydia psittaci: a relevant cause of community-acquired pneumonia in two Dutch hospitals
S M C Spoorenberg1, W J W Bos, E J van Hannen
1Department of Internal Medicine, St. Antonius Hospital, Nieuwegein, the Netherlands.
Background:
Of all hospitalised community-acquired pneumonias (CAPs) only a few are known to be caused by Chlamydia psittaci. Most likely the reported incidence, ranging from of 0% to 2.1%, is an underestimation of the real incidence, since detection of psittacosis is frequently not incorporated in the routine microbiological diagnostics in CAP or serological methods are used.
Methods:
C. psittaci real-time polymerase chain reaction (PCR) was routinely performed on the sputum of 147 patients hospitalised with CAP, who participated in a clinical trial conducted in two Dutch hospitals. In 119/147 patients the paired complement fixation test (CFT) was also performed for the presence of Chlamydia antibodies. Positive CFTs were investigated by micro- Immunofluorescence for psittacosis specificity. Case criteria for psittacosis were a positive PCR or a fourfold rise of antibody titre in CFT confirmed by micro- Immunofluorescence. Furthermore, we searched for parameters that could discriminate psittacosis from CAPs with other aetiology.
Results:
7/147 (4.8%) patients were diagnosed with psittacosis: six with PCR and one patient with a negative PCR, but with CFT confirmed by micro- Immunofluorescence. Psittacosis patients had had a higher temperature (median 39.6 vs. 38.2 °C;) but lower white blood cell count (median 7.4 vs. 13.7 x 109/l) on admission compared with other CAP patients.
Conclusion:
In this study, C. psittaci as CAP-causing pathogen was much higher than previously reported. To detect psittacosis, PCR was performed on all CAP patients for whom a sputum sample was available. For clinical use, PCR is a fast method and sputum availability allows genotyping; additional serology can optimise epidemiological investigations.
Insights
Psittacosis, caused by Chlamydia psittaci, is a more frequent cause of community-acquired pneumonia (CAP) than previously thought. Real-time PCR on sputum is an effective diagnostic method for identifying this pathogen in CAP patients.
Area of Science:
- Infectious Diseases
- Respiratory Medicine
- Microbiology
Background:
- Community-acquired pneumonia (CAP) is often diagnosed without specific etiological identification.
- Chlamydia psittaci, the causative agent of psittacosis, is an under-recognized cause of CAP, with reported incidences often below 2.1% due to diagnostic limitations.
Purpose of the Study:
- To determine the incidence of psittacosis in hospitalized CAP patients using molecular diagnostics.
- To identify clinical parameters that differentiate psittacosis from other causes of CAP.
Main Methods:
- Real-time polymerase chain reaction (PCR) was performed on sputum samples from 147 hospitalized CAP patients.
- Complement fixation test (CFT) and micro-immunofluorescence were used for serological confirmation of Chlamydia antibodies.
- Clinical data, including temperature and white blood cell count, were analyzed to distinguish psittacosis from other CAP etiologies.
Main Results:
- Psittacosis was diagnosed in 4.8% (7/147) of hospitalized CAP patients, a higher incidence than previously reported.
- Patients with psittacosis presented with higher temperatures (median 39.6°C) and lower white blood cell counts (median 7.4 x 10^9/L) on admission compared to other CAP patients.
- PCR identified the pathogen in six cases, while serology confirmed one additional case with a negative PCR.
Conclusions:
- Chlamydia psittaci is a more significant pathogen in CAP than previously recognized.
- Real-time PCR on sputum is a rapid and effective method for diagnosing psittacosis in CAP patients.
- Combining PCR with serology enhances etiological diagnosis and epidemiological investigation of psittacosis.
Related Concept Videos
01:29Bacterial Phylum Chlamydiae
01:14Atypical Pneumonia
01:30Pneumonia I: Introduction
Risk Factors
Various factors influence the likelihood of developing pneumonia. Age plays a crucial role, with infants, children under two, and individuals over 65 at increased risk due to their...
01:30Pneumonia III: Complications and Assessment
01:26Sexually Transmitted Infections
01:28Pneumonia IV: Management
Bacterial Pneumonia Treatment
For bacterial pneumonia, antibiotics serve as the cornerstone of therapy. Initial treatment often begins with empirical antibiotics, tailored to the anticipated causative organism and adjusted based on culture results. Key antibiotic choices include: