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Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
Expression of capsular polysaccharide during experimental focal infection with Staphylococcus aureus
1Infectious Diseases Section, Veterans Administration Medical Center, Boston, Massachusetts 02130.
Abstract:
In vivo expression of the type 8 capsular polysaccharide (CP) of Staphylococcus aureus was studied by using the Becker strain, the prototype type 8 strain, in a guinea pig model of persistent subcutaneous infection. At 24 hr after infection, supernatants of aspirates from the site of infection contained low levels of CP (median, 0.53 ng/ml; range, less than 0.16-6.30 ng/ml). CP levels increased at day 3 to a geometric mean level of 47 ng/ml, at day 6 to 389 ng/ml, at day 8 to 537 ng/ml, and thereafter persisted in that range. On days 1, 3, and 6, CP was not detectable (less than 0.16 ng/ml) in the serum, but on days 8, 10, or 13, CP was present in 15 (58%) of 26 animals; the median peak level of serum CP among these animals was 2.00 ng/ml (range, 0.31-5.90 ng/ml). These studies document that the type 8 CP of S. aureus is produced and released during a focal, suppurative infection and can be detected in the serum of infected animals.
Insights
Staphylococcus aureus type 8 capsular polysaccharide (CP) was measured in guinea pigs with a persistent infection. CP levels rose significantly in infection sites and were detected in serum by day 8.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Staphylococcus aureus is a significant human pathogen.
- The type 8 capsular polysaccharide (CP) is a key virulence factor.
- Understanding CP expression in vivo is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the in vivo expression and release of type 8 CP during a persistent Staphylococcus aureus infection.
- To quantify CP levels at the infection site and in serum over time.
Main Methods:
- Utilized a guinea pig model of persistent subcutaneous infection with the Staphylococcus aureus Becker strain.
- Collected aspirates from infection sites and serum samples at various time points post-infection.
- Quantified type 8 CP levels using immunoassay techniques.
Main Results:
- Type 8 CP levels were low at 24 hours post-infection but increased significantly by day 3, reaching a plateau by day 8.
- CP was detected in the serum of 58% of infected animals by day 8, with median peak levels of 2.00 ng/ml.
- These findings demonstrate the production and release of type 8 CP during a focal, suppurative infection.
Conclusions:
- Type 8 CP of Staphylococcus aureus is actively produced and released during persistent infections.
- Serum detection of type 8 CP is possible during the course of infection.
- This study provides valuable insights into the in vivo behavior of type 8 CP, potentially aiding in diagnostic and therapeutic strategies.
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