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Clonal and capsular types decide whether pneumococci will act as a primary or opportunistic pathogen
K Sjöström1, C Spindler, A Ortqvist
1Department of Bacteriology, Swedish Institute for Infectious Disease Control, Karolinska University Hospital, Solna, Sweden.
Summary
Certain Streptococcus pneumoniae serotypes (1 and 7F) are primary pathogens causing less severe disease, while others are opportunistic, leading to more severe invasive pneumococcal disease, particularly in those with underlying conditions.
Area of Science:
- Microbiology
- Infectious Diseases
- Epidemiology
Background:
- Streptococcus pneumoniae causes significant global morbidity and mortality.
- The specific impact of capsular and clonal types on invasive pneumococcal disease (IPD) severity requires further elucidation.
Purpose of the Study:
- To investigate the correlation between capsular serotypes, clonal types, and the severity of invasive pneumococcal disease in adult patients.
- To identify specific pneumococcal types associated with increased disease severity and mortality.
Main Methods:
- Analysis of 494 adult patients diagnosed with invasive pneumococcal disease.
- Correlation of disease severity and type with patient demographics (age, underlying disease) and pathogen characteristics (capsular serotype, clonal type).
- Assessment of disease severity using APACHE II scores and mortality rates.
Main Results:
- Serotypes 1 and 7F isolates were genetically homogenous, primarily infecting younger, healthy individuals with no associated mortality.
- Other serotypes, such as 23F, were more prevalent in elderly patients.
- Specific clones of serotypes 3 and 11A were associated with higher APACHE II scores and increased mortality.
- Penicillin resistance did not demonstrate a significant impact on disease severity or type.
Conclusions:
- Clones with capsular types 1 and 7F act as primary pathogens with high invasive potential but lower disease severity.
- Clones with other capsular types are more opportunistic, predominantly affecting individuals with underlying conditions, and can cause more severe disease.