[Current microbiologic problems. Pulmonary infection by Streptococcus pneumoniae. Current physiopathological aspects].
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.
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.
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.


CONCLUSIONS
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.
Bédos
J P
JP
Institut National de la Santé et de la Recherche Médicale U13 (JPB), Groupe Hospitalier Bichat-Claude Bernard, Paris.
Rivier
C
C
Azoulay-Dupuis
E
E
Moine
P
P
D006801:Humans; D018410:Pneumonia, Bacterial / Q000382:microbiology* / Q000503:physiopathology; D011446:Prospective Studies; D012720:Severity of Illness Index; D013290:Streptococcal Infections / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000472:pathogenicity*; D014774:Virulence