High incidence of septic shock caused by Streptococcus pneumoniae serotype 3-a retrospective epidemiological study

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title = "High incidence of septic shock caused by Streptococcus pneumoniae serotype 3-a retrospective epidemiological study",
abstract = "Background: More than 90 immunologically distinct serotypes of Streptococcus pneumoniae exist, and it is not fully elucidated whether the serotype is a risk factor for severity of invasive pneumococcal disease (IPD). Our hypothesis is that serotypes differ in their capacity to cause septic shock. Methods: We performed a retrospective study in Southern Sweden based upon 513 patients with IPD in the pre-vaccine era 2006-2008. The serotype, co-morbidity, and sepsis severity were determined. Serotypes were compared to serotype 14 as a reference and grouped according to their invasive potential, that is, high (serogroups 1, 5 and 7), intermediate (serogroups 4, 9, 14 and 18) and, finally, low invasive potential (serogroups 3, 6, 8, 15, 19, 23 and 33). Results: Patients with S. pneumoniae serotype 3 had significantly more often septic shock (25{\%}, odds ratio (OR) 6.33 [95{\%} confidence interval (CI) 1.59-25.29]), higher mortality (30{\%}, OR 2.86 [CI 1.02-8.00]), and more often co-morbidities (83{\%}, OR 3.82 [CI 1.39-10.54]) when compared to serotype 14. A significant difference in age and co-morbidities (p= 0.001) was found when patient data were pooled according to the invasive potential of the infecting pneumococci. The median age and percentage of patients with underlying co-morbidities were 72 years and 79{\%}, respectively, for serogroups associated with low invasiveness, 68 years and 61{\%}, respectively, for serogroups with intermediate invasiveness, and, finally, 62 years and 48{\%}, respectively, for serogroups with high invasiveness. No difference in sepsis severity was found between the three groups. Conclusions: S. pneumoniae serotype 3 more often caused septic shock compared to serotype 14. Our results support the hypothesis that serotypes with high invasiveness mainly cause IPD in younger patients with less co-morbidities. In contrast, serogroups with low and intermediate invasive potential mostly cause IPD in the elderly with defined co-morbidities, and thus can be considered as opportunistic.",
keywords = "Invasive pneumococcal disease, Sepsis, Serotype 3, Serotype 19F, Streptococcus pneumoniae",
author = "Jonas Ahl and Nils Littorin and Arne Forsgren and Inga Odenholt and Fredrik Resman and Kristian Riesbeck",
year = "2013",
doi = "10.1186/1471-2334-13-492",
language = "English",
volume = "13",
journal = "BMC Infectious Diseases",
issn = "1471-2334",
publisher = "BioMed Central (BMC)",