[Relationship between virulence and resistance to antibiotics in pneumococci. Contribution of experimental data obtained in an animal model].

Epidemiologic data show that the organ affinity of Streptococcus pneumoniae varies across serotypes. As a result of this heterogeneous distribution, exposure to antimicrobials is greater for serotypes 6, 14, 19 and 23. Most strains with resistance to antimicrobials are found among these four serotypes. Virulence of the various serotypes of pneumococci varies with adhesion, enzyme secretion, and resistance to phagocytosis. In a mouse model of experimental septicemia, neither the origin of strains nor the acquisition of a resistant phenotype modified virulence, which appeared as an intrinsic feature specific to each phenotype. Strains belonging to serotypes 6, 14, 19 and 23 with or without resistance to antimicrobials were only very rarely virulent in the experimental model used. As an indirect result, resistance to antimicrobials and virulence were inversely related among the strains of S. pneumoniae tested.