Population snapshot of emergent Streptococcus pneumoniae serotype 19A in the United States, 2005

Matthew R. Moore, Robert E. Gertz, Robyn L. Woodbury, Genevieve A. Barkocy-Gallagher, William Schaffner, Catherine Lexau, Kenneth Gershman, Arthur Reingold, Monica Farley, Lee H. Harrison, James L. Hadler, Nancy M. Bennett, Ann R. Thomas, Lesley McGee, Tamara Pilishvili, Angela B. Brueggemann, Cynthia G. Whitney, James H. Jorgensen, Bernard Beall

Research output: Contribution to journalArticlepeer-review

434 Scopus citations


Background. Serotype 19A invasive pneumococcal disease (IPD) increased annually in the United States after the introduction of the 7-valent conjugate vaccine (PCV7). To understand this increase, we characterized serotype 19A isolates recovered during 2005. Methods. IPD cases during 1998-2005 were identified through population-based surveillance. We performed susceptibility testing and multilocus sequence typing on 528 (95%) of 554 serotype 19A isolates reported in 2005. Results. The incidence of IPD due to serotype 19A increased from 0.8 to 2.5 cases per 100,000 population between 1998 and 2005 (P < .05), whereas the overall incidence of IPD decreased from 24.4 to 13.8 cases per 100,000 population (P < .05). Simultaneously, the incidence of IPD due to penicillin-resistant 19A isolates increased from 6.7% to 35% (P < .0001). Of 151 penicillin-resistant 19A isolates, 111 (73.5%) belonged to the rapidly emerging clonal complex 320, which is related to multidrug-resistant Taiwan 19F-14. The remaining penicillin-resistant strains were highly related to other clones of PCV7 serotypes or to isolates within major 19A clonal complex 199 (CC199). In 1999, only CC199 and 3 minor clones were apparent among serotype 19A isolates. During 2005, 11 multiple-isolate clonal sets were detected, including capsular switch variants of a serotype 4 clone. Conclusions. PCV7 ineffectiveness against serotype 19A, antibiotic resistance, clonal expansion and emergence, and capsular switching have contributed to the genetic diversity of 19A and to its emergence as the predominant invasive pneumococcal serotype in the United States.

Original languageEnglish (US)
Pages (from-to)1016-1027
Number of pages12
JournalJournal of Infectious Diseases
Issue number7
StatePublished - Apr 1 2008
Externally publishedYes

ASJC Scopus subject areas

  • Immunology and Allergy
  • Infectious Diseases


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