Background: Recurrent systemic pneumococcal infection usually occurs in immunocompromised patients and patients with underlying conditions.
Methods: Between 1993 and 2006, investigators at 8 pediatric hospitals prospectively identified cases of invasive pneumococcal disease (IPD) and retrospectively documented demographics and clinical information. Antibiotic susceptibility was determined for penicillin and ceftriaxone by microbroth dilution. Isolates were serotyped and molecular relatedness determined using pulse field gel electrophoresis (PFGE).
Results: Four thousand sixty-seven children were diagnosed with IPD over 12.3 years. One hundred and 8 episodes of recurrent disease were seen in 90 children (2.6%); 75 experienced 2 infections, 12 experienced 3 infections and 3 experienced 4 infections. Fourteen of the 15 children with >2 episodes of infection had underlying conditions. The mean duration between 1st and 2nd infection was 22.9 weeks for children with no known underlying condition and 43.0 weeks for children with an underlying condition (P = 0.001). Seventy episodes of IPD among the 90 patients were caused by a different serotype or a different genotype as demonstrated by the PFGE. Sixteen children had intervals <30 days between infections; 7 were caused by different strains.
Conclusions: Approximately 80% of the children with recurrent invasive pneumococcal disease had underlying conditions. Seven of 16 children with recurrent infection <30 days apart were caused by acquisition of a new strain. Relapse of infection requires documentation that the pneumococcal isolates are not only the same serotype but also have the same PFGE patterns.