Pneumococcal necrotizing pneumonia in utah: Does serotype matter?

Background. Streptococcus pneumoniae is the most common cause of bacterial pneumonia in children. Despite the use of the 7- valent pneumococcal conjugate vaccine, the incidence of pneumococcal necrotizing pneumonia ( PNP) has been increasing. Our objectives were to describe temporal trends in PNP and to evaluate pneumococcal serotypes associated with PNP in Utah. Methods. We performed a retrospective review of all children <18 years of age who were cared for at a tertiary care children's hospital and who had blood, lung tissue, broncheoalveolar lavage, or pleural fluid cultures that grew S. pneumoniae, as well as radiographic evidence of pneumonia, from January 1997 through March 2006. All S. pneumoniae isolates were typed. Results. A total of 124 children with pneumococcal pneumonia were identified, and 33 (27%) of these children had radiographic evidence of PNP. During the period 1997 - 2000, 5 (13%) of 39 cases of culture- confirmed pneumococcal pneumonia were associated with PNP. In contrast, during the period 2001 - 2006, 28 (33%) of 85 pneumococcal pneumonia cases were complicated by PNP (odds ratio, 3.34; 95% confidence interval, 1.11 - 12.03). Non - 7- valent pneumococcal conjugate vaccine serotypes comprised 49% of the isolates during 1997 - 2000 and 88% of isolates during 2001 - 2006 (odds ratio, 7.89; 95% confidence interval, 2.91 - 21.90). Pneumonia due to serotype 3 was most often associated with PNP. Eleven (79%) of 14 cases of serotype 3 - associated pneumonia were associated with PNP. When compared with all other serotypes, serotype 3 was strongly associated with necrosis (odds ratio, 14.67; 95% confidence interval, 3.39 - 86.25). Conclusions. PNP is a serious and increasingly common complication of S. pneumoniae pneumonia in Utah. Infection with serotype 3 is associated with an increased risk of developing PNP. The increase in the incidence of infection due to nonvaccine serotypes reported worldwide and the changing epidemiology of invasive pneumococcal disease should be considered when developing vaccine strategies.