Influence of streptococcus pneumoniae serotypes in clinical outcomes of pneumonias

In adults, the influence of Streptococcus pneumoniae (Sp) serotypes on pneumonia mortality remains unclear. Aim: To describe the characteristics of adult patients with pneumonia caused by Sp isolated in invasive strains and the influence of different serotypes in clinical outcomes. Method: A retrospective study of Sp serotypes in invasive strains isolated from patients with pneumonia, describing the clinical features and complications. Blood and pleural fluid samples were processed using the BacT-Alert1 system. All strains were sent to the Reference Laboratory for serotyping. Serotypes were divided into 3 groups [1]: High invasive disease potential (H group): 1, 5 and 7 F; Low invasive potential (L group): 3, 6A, 6B, 8, 19F and 23F, the rest were named as other serotypes (O group). Results: Between January 2009 and December 2010 were isolated 53 Sp strains, 44 blood samples and 9 pleural fluid (3 patients had both). 18 of them were serotypes of H group, 10 were of L group, and 23 were of O group. There were a total of 50 patients (58% men). Mean age was 56y (±19). The table shows clinical outcomes. View this table: Clinical outcomes according to serotype Conclusions: Contrary to what colud be expected the pneumonies caused by Sp serotypes of H group had a lower mortality ratio.1 Brueggeman AB et al. Clonal relationships between Invasive and carriage S pneumoniae and serotype- and clone-specific differences in invasive disease potential. Reference: * 1. J Infect Dis. 2003 May 1; 187 (9):1424-32.