The recent introduction of the seven-valent pneumococcal conjugate vaccine has led to changes in the proportion of disease caused by different serotypes. The serotypes targeted by the vaccine have been reduced, and Streptococcus pneumonia serotype 19A is now the most commonly isolated serotype causing invasive pneumococcal disease. This serotype has been associated with antibiotic resistance. The authors of this article conducted a review of cases of invasive pneumococcal disease diagnosed between 2000 and 2010 in Calgary, Alberta, to examine the disease course of serotype 19A invasive pneumococcal disease compared with other serotypes.
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
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.
The Journal of Infectious Diseases 04/2008; 197(7):1016-27. DOI:10.1086/528996 · 6.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite the concern of replacement disease, notably by serotype 19A after 7-valent conjugate vaccine (PCV7) use, serotype 19A was increasingly recognized in Korean children before the introduction of PCV7. To understand the dynamics of serogroup 19 prevalence from 1991-2006, we serotyped 538 pediatric pneumococcal isolates. Serogroup 19 isolates (n = 126) were characterized by antimicrobial drug susceptibility, presence of mefA/ermB, and multilocus sequence typing. Overall, the proportion of serotype 19A isolates increased but serotype 19F decreased. Among children <5 years of age, the proportion of serotype 19A isolates in invasive pneumococcal disease increased from 0% in 1991-1994 to 8%-10% in 1995-2000, reached 26% in 2001-2003, and remained at 20% in 2004-2006 when vaccine coverage did not exceed 25% (p = 0.005 for trend). This study demonstrates that the expansion of multidrug-resistant ST320 was responsible for the increase in serotype 19A before PCV7 use.
[Show abstract][Hide abstract] ABSTRACT: Recent studies have shown that some Streptococcus pneumoniae serotypes possess a higher potential to cause invasive disease than others. However, it is unknown whether disease potential for specific serotypes is similar for mucosal disease. Our objective was to assess the disease potential of individual S. pneumoniae serotypes causing invasive pneumococcal disease (IPD), acute otitis media (AOM) and acute conjunctivitis (AC) in children.
Serotypes of pneumococcal isolates from children with IPD, AOM and AC were compared with those carried by healthy children aged <3 years. All children resided in the same area and were studied during the same period. Odds ratios for disease were calculated for each diagnosis following multivariate analysis, including gender, age, ethnic group, previous antibiotic treatment and year variability.
A total of 5,500 isolates were collected: 189 from blood or cerebrospinal fluid, 3,200 from middle ear fluid, 348 from conjunctiva and 1,763 from nasopharynx of healthy children. A significant positive association with IPD was demonstrated for serotypes 1, 5 and 12F; with AOM for serotypes 1, 3, 5, 12F, 19A and 19F; and with AC for serotype 3 and nontypeable S. pneumoniae. A significant negative association with IPD was demonstrated for nontypeable S. pneumoniae and with AOM for serotypes 6A, 6B, 15A and nontypeable S. pneumoniae.
Our results reflect the importance of the polysaccharide capsule in site-specific disease potential and provide useful information regarding disease potential of nonvaccine serotypes shown to be involved in carriage replacement after vaccination with the 7-valent conjugate vaccine.
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