Serotype specific invasive capacity and persistent reduction in invasive pneumococcal disease

Abstract

Defining the propensity of Streptoccocus pneumoniae (SP) serotypes to invade sterile body sites following nasopharyngeal (NP) acquisition has the potential to inform about how much invasive pneumococcal disease (IPD) may occur in a typical population with a given distribution of carriage serotypes. Data from enhanced surveillance for IPD in Massachusetts children ≤7 years in 2003/04, 2006/07 and 2008/09 seasons and surveillance of SP NP carriage during the corresponding respiratory seasons in 16 Massachusetts communities in 2003/04 and 8 of the 16 communities in both 2006/07 and 2008/09 were used to compute a serotype specific “invasive capacity (IC)” by dividing the incidence of IPD due to serotype x by the carriage prevalence of that same serotype in children of the same age. A total of 206 IPD and 806 NP isolates of SP were collected during the study period. An approximate 50-fold variation in the point estimates between the serotypes having the highest (18C, 33F, 7F, 19A, 3 and 22F) and lowest (6C, 23A, 35F, 11A, 35B, 19F, 15A, and 15BC) IC was observed. Point estimates of IC for most of the common serotypes currently colonizing children in Massachusetts were low and likely explain the continued reduction in IPD from the pre-PCV era in the absence of specific protection against these serotypes. Invasive capacity differs among serotypes and as new pneumococcal conjugate vaccines are introduced, ongoing surveillance will be essential to monitor whether serotypes with high invasive capacity emerge (e.g. 33F, 22F) as successful colonizers resulting in increased IPD incidence due to replacement serotypes.

Streptococcus pneumoniae Capsular Serotype Invasiveness Correlates with the Degree of Factor H Binding and Opsonization with C3b/iC3b

“…The capsule is the most important S. pneumoniae virulence factor and is classified into over 90 antigenically distinct capsular serotypes (1). The biology of S. pneumoniae varies markedly between serotypes (2)(3)(4)(5)(6)(7)(8), and understanding the mechanisms causing these differences will help identify characteristics required for virulence. For example, for each episode of carriage in the nasopharynx, some serotypes of S. pneumoniae are much more likely than others to cause invasive disease (defined as isolation of S. pneumoniae from a sterile site, mainly the blood) (5,6,8).…”

“…The biology of S. pneumoniae varies markedly between serotypes (2)(3)(4)(5)(6)(7)(8), and understanding the mechanisms causing these differences will help identify characteristics required for virulence. For example, for each episode of carriage in the nasopharynx, some serotypes of S. pneumoniae are much more likely than others to cause invasive disease (defined as isolation of S. pneumoniae from a sterile site, mainly the blood) (5,6,8). Epidemiological studies have used the ratio of cases to carriers to provide estimates for relative serotype invasiveness, which can be represented as the number of cases of invasive disease per 100,000 colonization events (the attack rate) (5) or as case-to-carrier ratios (6,8).…”

“…For example, for each episode of carriage in the nasopharynx, some serotypes of S. pneumoniae are much more likely than others to cause invasive disease (defined as isolation of S. pneumoniae from a sterile site, mainly the blood) (5,6,8). Epidemiological studies have used the ratio of cases to carriers to provide estimates for relative serotype invasiveness, which can be represented as the number of cases of invasive disease per 100,000 colonization events (the attack rate) (5) or as case-to-carrier ratios (6,8). With some exceptions, the different data sets identify similar sets of serotypes as being more invasive, but the reasons underpinning the link between a serotype and invasiveness are poorly understood.…”

Investigation of Bacterial Meningitis Agents from Patients with Suspicion of Non-Neonatal Meningitis by Conventional and Molecular Methods

“…Yıldırım ve ark. (27) yaptıkları çalışmada, invaziv hastalığa yol açma potansiyeli en yüksek olan serotipleri 3, 7F, 18C, 19A, 22F ve 33F olarak bildirmişler-dir. Aslan ve ark.…”

The new first-line defense: the potential of nasopharyngeal colonization in vaccine strategies

“…This restricted serotype coverage has led to the replacement of S. pneumoniae vaccine serotypes by non-vaccine serotypes as both colonizers of the nasopharynx and causes of disease. 31,[41][42][43] Hence, there is a strong interest in alternative vaccine strategies that target all S. pneumoniae strains and could also prevent lung infection.…”