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Changes in the spectrum of organisms causing respiratory tract infections: a review
1Institute of Medical Microbiology, University of Zurich, Switzerland.
Abstract:
Over the last decade, the spectrum of organisms causing community-acquired acute lower respiratory tract infections has changed. Streptococcus pneumoniae now causes approximately 30% of outpatient acute pneumonia-less than in former decades-whereas Mycoplasma pneumoniae is found in both young and elderly patients. The Enterobacteriaceae and Staphylococcus aureus are now seen more frequently as respiratory tract pathogens in community-acquired pneumonia patients, and they are the major organisms causing pneumonia in residents of homes for the elderly or nursing homes, and in immuno-compromised patients. Agents that were previously considered non-pathogenic for the respiratory tract include serotypes of Haemophilus influenzae other than type b, H. parainfluenzae and Moraxella (Branhamella) catarrhalis; these organisms affect mainly patients with underlying cardiopulmonary disease. Legionella species can cause sporadic as well as epidemic disease of the lower respiratory tract. Chlamydia pneumoniae is a newly recognized pathogen responsible for mild to severe upper and lower respiratory tract infections. In 60-80% of cases, hospital-acquired pneumonias are caused by Gram-negative bacilli and S. aureus. These organisms colonize the mucosal membranes of the upper respiratory tract and penetrate into the lower tract by aspiration or intubation.
Insights
The spectrum of respiratory pathogens has shifted, with Streptococcus pneumoniae decreasing and Mycoplasma pneumoniae, Enterobacteriaceae, and Staphylococcus aureus becoming more prevalent in community-acquired pneumonia. New pathogens like Haemophilus influenzae and Chlamydia pneumoniae also contribute to respiratory infections.
Area of Science:
- Infectious Diseases
- Microbiology
- Pulmonology
Background:
- The microbial landscape of community-acquired acute lower respiratory tract infections has evolved over the past decade.
- Shifts in causative agents necessitate updated understanding for effective treatment and prevention strategies.
Purpose of the Study:
- To delineate the changing spectrum of bacterial and atypical pathogens responsible for community-acquired acute lower respiratory tract infections.
- To identify emerging and increasingly prevalent microorganisms in respiratory infections across different patient populations.
Main Methods:
- This study is a review of current literature and clinical observations regarding respiratory tract infections.
- Analysis of epidemiological data on the prevalence of various pathogens in community-acquired pneumonia (CAP) and hospital-acquired pneumonia (HAP).
Main Results:
- Streptococcus pneumoniae now accounts for about 30% of outpatient pneumonia, a decrease from previous decades.
- Mycoplasma pneumoniae is increasingly identified in both young and elderly patients.
- Enterobacteriaceae and Staphylococcus aureus are more frequent in CAP, especially in nursing home residents and immunocompromised individuals.
- Previously non-pathogenic organisms like Haemophilus influenzae (non-type b), H. parainfluenzae, and Moraxella (Branhamella) catarrhalis are noted in patients with underlying cardiopulmonary disease.
- Legionella species cause sporadic and epidemic lower respiratory tract infections.
- Chlamydia pneumoniae is a newly recognized pathogen causing a range of respiratory infections.
- Gram-negative bacilli and S. aureus are responsible for 60-80% of hospital-acquired pneumonias.
Conclusions:
- The spectrum of pathogens causing lower respiratory tract infections has significantly changed, requiring updated diagnostic and therapeutic approaches.
- Increased prevalence of certain bacteria and atypical organisms highlights the need for continued surveillance and research in respiratory infections.