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Published on: February 23, 2014
Etiology of community-acquired pneumonia: increased microbiological yield with new diagnostic methods
Niclas Johansson1, Mats Kalin, Annika Tiveljung-Lindell
1Department of Medicine, Karolinska Institutet, Stockholm, Sweden. sniclas.johansson@karolinska.se
Background:
The microbial etiology of community-acquired pneumonia (CAP) is still not well characterized. During the past few years, polymerase chain reaction (PCR)-based methods have been developed for many pathogens causing respiratory tract infections. The aim of this study was to determine the etiology of CAP among adults-especially the occurrence of mixed infections among patients with CAP-by implementing a new diagnostic PCR platform combined with conventional methods.
Methods:
Adults admitted to Karolinska University Hospital were studied prospectively during a 12-month period. Microbiological testing methods included culture from blood, sputum, and nasopharyngeal secretion samples; sputum samples analyzed by real-time quantitative PCR for Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis; nasopharyngeal specimens analyzed by use of PCR; serological testing for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and viruses common in the respiratory tract; and urine antigen assays for detection of pneumococcal and Legionella pneumophila antigens.
Results:
A microbial etiology could be identified for 67% of the patients (n = 124). For patients with complete sampling, a microbiological agent was identified for 89% of the cases. The most frequently detected pathogens were S. pneumoniae (70 patients [38%]) and respiratory virus (53 patients [29%]). Two or more pathogens were present in 43 (35%) of 124 cases with a determined etiology.
Conclusions:
By supplementing traditional diagnostic methods with new PCR-based methods, a high microbial yield was achieved. This was especially evident for patients with complete sampling. Mixed infections were frequent (most commonly S. pneumoniae together with a respiratory virus).
Insights
This study used advanced PCR methods to identify the causes of community-acquired pneumonia (CAP) in adults. It found that mixed infections, often involving Streptococcus pneumoniae and respiratory viruses, are common.
Area of Science:
- Infectious Diseases
- Microbiology
- Respiratory Medicine
Background:
- The microbial causes of community-acquired pneumonia (CAP) remain incompletely understood.
- Polymerase chain reaction (PCR) techniques have advanced the diagnosis of respiratory pathogens.
- A comprehensive etiological investigation of CAP is crucial for effective treatment.
Purpose of the Study:
- To determine the microbial etiology of CAP in adults.
- To assess the prevalence of mixed infections in CAP patients.
- To evaluate a novel diagnostic PCR platform combined with conventional methods.
Main Methods:
- Prospective study of adult CAP patients over 12 months at Karolinska University Hospital.
- Utilized culture, real-time quantitative PCR for key bacteria (S. pneumoniae, H. influenzae, M. catarrhalis), PCR for nasopharyngeal specimens, serology for atypical pathogens and viruses, and urine antigen assays.
- Comprehensive microbiological testing including blood, sputum, and nasopharyngeal samples.
Main Results:
- Microbial etiology identified in 67% of patients (124/185).
- For patients with complete sampling, etiology was identified in 89% of cases.
- Most frequent pathogens: S. pneumoniae (38%) and respiratory viruses (29%). Mixed infections (≥2 pathogens) occurred in 35% of cases with identified etiology.
Conclusions:
- Combining traditional diagnostics with new PCR methods significantly improved etiological yield in CAP.
- Complete sampling enhanced the identification of causative agents.
- Mixed infections, particularly S. pneumoniae with respiratory viruses, are a frequent finding in adult CAP.
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Enhance airway patency
Position the patient correctly to facilitate drainage of the affected lung segments. Manual or mechanical percussion and vibration can also be employed.