Invasive Streptococcus pneumoniae serotypes associated with in-patient and out-patient isolates from the United States

Article Outline

• Copyright

Background: Streptococcus pneumoniae (SPN) is a major cause of invasive diseases and upper respiratory tract infections. Introduction of the pneumococcal conjugate 7-valent vaccine (PV7) into the US childhood vaccine schedule in 2000 has significantly reduced invasive pneumococcal disease in children and adults, with concurrent reduction in the seven vaccine serotypes. Consistent monitoring of possible replacement serotypes is essential to determine possible antibiotic resistance patterns as certain serotypes are more closely associated with antibiotic resistance, as well as to determine targets for future vaccines. In this study we evaluate the serotypes of invasive SPN isolates from in-patients and outpatients from 2004.

Methods: The capsular serotypes of 275 invasive SPN isolates collected in the US through the Tigecycline Evaluation Surveillance Trial were determined using sequential multiplex PCR and confirmed using the Quellung reaction. Invasive isolates were defined as those from normally sterile sites, such as blood, CSF and other body fluid.

Results: In the following table.

• 
  • View Large Image
  • Download to PowerPoint

*nt=non-typeable.

Conclusion: While PV7 serotypes have declined since 2000, in 2004 approximately 20% of the invasive isolates from this study were from the seven vaccine types (4, 6B, 9V, 14, 18C, 19F, 23F). In-patients and out-patients were equally likely to carry PV7 serotypes. Serotype 19A was the most common serotype in both in- and out-patients, which is cause for concern as this serotype is often non-susceptible to penicillin and erythromycin. In-patients were more likely to carry non-typeable isolates, while equal percentages of isolates from both groups were non-encapsulated. Continued monitoring of post-vaccine serotype trends will be vital to the management of pneumococcal disease.