Genetic characteristics of pneumococcal disease in elderly patients before introducing the pneumococcal conjugate vaccine

Abstract

Streptococcus pneumoniae strains causing invasive pneumococcal disease (IPD) in the elderly population of England and Wales during the winter of 2003/2004 (1 November 2003 to 30 April 2004) were characterized by serotyping and genotyping in order to determine their population structure in the elderly. Serotyping and multilocus sequence typing (MLST) were carried out on 542 invasive isolates referred to the Respiratory and Systemic Infection Laboratory. Pneumococci were distributed among 32 serotypes and 144 MLST sequence types. A high genetic diversity was observed within the major serotypes. Genetic relatedness varied with regard to serotype. Isolates within serotypes 3, 7F and 8 were the most genetically related whereas serotypes 6A and 19F comprised isolates originating from unrelated ancestors. There was indirect evidence that some pneumococci were derived from clones that had undergone capsular switching in the past. Interestingly one case of IPD was caused by a pneumococcus originating from a clone that had undergone capsular switching from serotype 18C, a serotype included in 7-valent pneumococcal conjugate vaccine (PCV) to serotype 1 (serotype not included in PCV) suggesting that virulent clones with the potential ability to evade PCV existed in the pneumococcal population prior to the routine introduction of this vaccine. Isolates from 28 cases of apparent 23-valent pneumococcal polysaccharide vaccine (PPV) failure were included but there was no evidence of the emergence of particular clones associated with vaccine failures. Longitudinal studies based on serotypic and genetic characterization of pneumococci are fundamental to understanding the impact of both PPV and PCV on the genetic structure of pneumococcal populations.

Rapid Spread of Pneumococcal Nonvaccine Serotype 7C Previously Associated with Vaccine Serotype 19F, England and Wales

“…ST177 has been associated with serotype 19F, with 39/42 isolates submitted to the PubMLST isolates database associated with this serotype ( https://pubmlst.org/spneumoniae/ ). In England and Wales, ST177 was represented exclusively by serotype 19F in elderly patients before PCV7 introduction ( 13 ). Because serotypes 19F and 24F are common causes of IPD, we were unable to sequence all invasive isolates.…”

Changes in Molecular Epidemiology of Streptococcus pneumoniae Causing Meningitis following Introduction of Pneumococcal Conjugate Vaccination in England and Wales

“…Repeat samples of the same serotype from the same patient within a 30-day period were considered to represent the same episode and were therefore excluded from subsequent analyses. Multilocus sequence typing (MLST) was carried out using a method described previously, and sequence types (STs) were allocated using the online MLST database (www .mlst.net) (13). Sequence data were processed using the Bionumerics pipeline (14).…”

Multiple-locus variable-number tandem-repeat analysis of Streptococcus pneumoniae and comparison with multiple loci sequence typing

“…331 invasive isolates of Streptococcus pneumoniae from the Health Protection Agency collection, London, UK, collected during the period 2002–2006, were selected among the 10 major MLST sequence types (STs), circulating in England and Wales (see [27] and [28] for detailed MLST methodology), with approximately 30 isolates per ST. Selection included serotypes commonly associated with these STs and all possible serotype variants (Table 1) identified in the HPA collection.…”