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[Current microbiologic problems. Pulmonary infection by Streptococcus pneumoniae. Current physiopathological aspects]
J P Bédos1, C Rivier, E Azoulay-Dupuis
1Institut National de la Santé et de la Recherche Médicale U13 (JPB), Groupe Hospitalier Bichat-Claude Bernard, Paris.
Abstract:
STILL A SERIOUS DISEASE: Despite advances in antibiotic therapy, and despite the emergence of beta-lactam-resistant strains, mortality of pneumococcal pneumonia has remained relatively unchanged. The pathogenicity of a pneumococcal strain results from an interaction between a specific host with its own capacity to "resist or yield" to the multiple virulence factors intrinsic to each S. pneumoniae strain.
Role Of The Capsule:
The capsule is the pneumococci's principal arm of resistance against the host's defense systems. There is a wide variability depending on the capsule serotype. Inversely, the capsule plays no role in triggering the inflammatory reaction which is secondary to substances released from the bacterial wall such as teichoic acid and peptidoglycan.
Host Response:
The molecular mechanisms of cellular activation and induction of proinflammatory cytokines triggered by S. pneumoniae follow similar pathways which are different from those for endotoxin triggered by Gram negative bacteria.
Perspectives:
A better understanding of the clinical expression, distinguishing simple nasopharyngeal carriage from bacterial pneumonia should lead to the design of new therapeutic agents which will reduce the capacity of certain S. pneumoniae strains to invade the host and trigger deleterious inflammatory reactions.
Insights
Pneumococcal pneumonia remains a serious disease with unchanged mortality despite antibiotics. Understanding Streptococcus pneumoniae virulence factors and host response is key to developing new therapies.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Context:
- Pneumococcal pneumonia exhibits persistent high mortality despite advances in antibiotic treatments.
- The emergence of beta-lactam-resistant Streptococcus pneumoniae strains complicates treatment strategies.
- Pathogenicity arises from the complex interplay between pneumococcal virulence factors and host defense mechanisms.
Purpose:
- To elucidate the role of Streptococcus pneumoniae virulence factors, particularly the capsule, in host-pathogen interactions.
- To investigate the molecular mechanisms of host cellular activation and cytokine induction by S. pneumoniae.
- To differentiate between nasopharyngeal carriage and invasive pneumococcal pneumonia for improved therapeutic targeting.
Summary:
- The pneumococcal capsule is a primary defense against host immune systems, with serotype variability influencing pathogenicity.
- Bacterial wall components like teichoic acid and peptidoglycan trigger inflammatory responses, distinct from Gram-negative endotoxin pathways.
- S. pneumoniae activates host cells and induces proinflammatory cytokines via molecular pathways differing from those initiated by Gram-negative bacteria.
Impact:
- Enhanced understanding of pneumococcal pathogenesis can guide the development of novel therapeutic agents.
- New treatments could target S. pneumoniae's capacity to invade hosts and provoke harmful inflammatory reactions.
- Distinguishing between carriage and pneumonia is crucial for designing effective interventions against this persistent infectious disease.