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Community-acquired pneumonia: role of atypical organisms
R Cosentini1, P Tarsia, F Blasi
1Department of Emergency Medicine, IRCCS Ospedale Maggiore di Milano, Divisione Medicina d'Urgenza, Via F. Sforza, 35, 20122 Milan, Italy. medurg3@polic.cilea.it
Abstract:
M. pneumoniae infection occurs world-wide and is the most common cause of community-acquired pneumonia (CAP) in the 5 to 20 year-old age group. The most reliable diagnostic test is enzyme immunoassay that allows immunoglobulin (Ig)G and IgM titration and presents 92% sensitivity and 95% specificity on paired samples. Potentially active drugs are tetracyclines, macrolides, ketolides, lincosamides, streptogamines, chloramphenicol, and fluoroquinolones. The incidence of Legionella infection, in spite of its world-wide diffusion, is highly variable in different studies, ranging from 1% to 27% of CAP. The most likely mode of transmission is direct inhalation from Legionella-contaminated water-supply systems. Extrapulmonary manifestations are relatively common but nonspecific. However, some signs and symptoms may raise the suspicion of Legionella infection: a sputum Gram stain with a high number of neutrophils without any organism, hyponatremia, and diarrhea in a critically ill patient. Urinary radioimmunoassay (RIA) antigen detection is the method of choice for L. pneumophila serogroup 1. The best treatment regimen is a full three-week treatment with a macrolide (erythromycin, clarithromycin, azithromycin). An alternative treatment regimen may be the association of second generation fluoroquinolones with tetracyclines. A notable improvement in most of the new fluoroquinolones is their activity against Legionella, so that their use as single agent may be hypothesised even if clinical data are still insufficient for a definitive indication. Chlamydia pneumoniae account for 6-20% of CAP depending on several factors such as setting of the studied population, age group examined, and diagnostic methods used. The current gold standard for serological diagnosis of acute infection is microimmunofluorescence testing. Tetracyclines and erythromycin show good in vitro activity and so far have been the most commonly employed drugs in the treatment of C. pneumoniae infection. New macrolides, ketolides, and new fluoroquinolones are other potentially effective drugs.
Insights
Mycoplasma pneumoniae, Legionella, and Chlamydia pneumoniae are common causes of community-acquired pneumonia (CAP). Diagnosis relies on enzyme immunoassays and antigen detection, with macrolides and tetracyclines being key treatments.
Area of Science:
- Infectious Diseases
- Microbiology
- Pulmonology
Background:
- Community-acquired pneumonia (CAP) is a significant global health concern.
- Mycoplasma pneumoniae, Legionella, and Chlamydia pneumoniae are key bacterial pathogens causing CAP, particularly in specific age groups.
- Accurate diagnosis and effective treatment are crucial for managing these infections.
Purpose of the Study:
- To review the epidemiology, diagnosis, and treatment of M. pneumoniae, Legionella, and C. pneumoniae infections causing CAP.
- To highlight diagnostic methods and effective therapeutic agents for these pathogens.
- To inform clinical practice regarding the management of common bacterial pneumonias.
Main Methods:
- Literature review of studies on M. pneumoniae, Legionella, and C. pneumoniae as causes of CAP.
- Analysis of diagnostic techniques including enzyme immunoassay, antigen detection, and microimmunofluorescence.
- Evaluation of antimicrobial agents and treatment regimens.
Main Results:
- M. pneumoniae is a common cause of CAP in younger individuals (5-20 years), diagnosed via enzyme immunoassay (92% sensitivity, 95% specificity).
- Legionella infection incidence varies (1-27% of CAP), transmitted via water systems; diagnosis uses urinary antigen detection, treated with macrolides.
- C. pneumoniae accounts for 6-20% of CAP, diagnosed by microimmunofluorescence, treated with tetracyclines and macrolides.
Conclusions:
- Effective diagnostic tools and targeted antimicrobial therapies are available for M. pneumoniae, Legionella, and C. pneumoniae.
- Macrolides, tetracyclines, and fluoroquinolones are primary treatment options.
- Continued research into new antimicrobial agents and treatment strategies is warranted.