Related Experiment Videos
Capsular transformation of a multidrug-resistant Streptococcus pneumoniae in vivo
1Laboratory of Microbiology, Rockefeller University, New York, New York 10021, USA.
Abstract:
Several multidrug-resistant (MDR) isolates of Streptococcus pneumoniae recovered from a variety of clinical sources and expressing serotypes 9N, 14, 19F, and 3 could not be distinguished from the capsular type 23 Spanish/USA epidemic clone in antibiotype, pulsed-field gel electrophoretic pattern, and restriction fragment length polymorphism types of their penicillin binding protein genes 1A, 2X, and 2B. When tested in a mouse model of virulence, isolates expressing capsular type 3 were lethal for 100% of infected animals within 2 days after intraperitoneal injection of 10(2) cfu/mouse. In contrast, several capsular type 23F isolates belonging to the MDR Spanish/USA clone and recovered from the same site were not lethal, even when injected at the dose of 10(7) cfu/mouse. These data suggest that the pneumococcal isolates expressing serotypes 9N, 14, 19F, and 3 represent products of in vivo capsular transformation events in which the MDR epidemic capsular type 23F Spanish/USA clone was the recipient.
Insights
Multidrug-resistant Streptococcus pneumoniae isolates with specific capsular types (9N, 14, 19F, 3) likely resulted from capsular transformation. The Spanish/USA epidemic clone (capsular type 23F) appears to be the recipient in these events.
Area of Science:
- Microbiology
- Molecular Biology
- Epidemiology
Background:
- Multidrug-resistant (MDR) Streptococcus pneumoniae strains pose significant public health challenges.
- Epidemic clones of Streptococcus pneumoniae are often associated with specific capsular types and antibiotic resistance patterns.
Purpose of the Study:
- To investigate the genetic relatedness and virulence of MDR Streptococcus pneumoniae isolates with different capsular types.
- To determine if certain capsular types represent in vivo transformation events involving an epidemic clone.
Main Methods:
- Antibiotype analysis to assess drug resistance profiles.
- Pulsed-field gel electrophoresis (PFGE) for genomic fingerprinting.
- Restriction fragment length polymorphism (RFLP) analysis of penicillin-binding protein genes.
- Mouse model of intraperitoneal infection to evaluate virulence.
Main Results:
- MDR isolates expressing capsular types 9N, 14, 19F, and 3 were indistinguishable from the Spanish/USA epidemic clone (capsular type 23F) based on antibiotype and genetic markers.
- Streptococcus pneumoniae isolates expressing capsular type 3 were highly lethal in a mouse model, causing 100% mortality at a low dose.
- In contrast, capsular type 23F isolates from the same epidemic clone showed low virulence, with no mortality even at a high dose.
Conclusions:
- The findings suggest that Streptococcus pneumoniae isolates with capsular types 9N, 14, 19F, and 3 have arisen through in vivo capsular transformation.
- The multidrug-resistant, epidemic capsular type 23F Spanish/USA clone likely served as the recipient in these transformation events.
- Capsular type switching may be a mechanism for the emergence and spread of novel, virulent pneumococcal strains.