RESUMEN
UNLABELLED: 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. BACKGROUND: Streptoccocus pneumoniae serotype 19A (ST19A) became an important cause of invasive pneumococcal disease (IPD) after the introduction of the conjugate vaccine. OBJECTIVE: To examine the severity and outcome of ST19A IPD compared with non-ST19A IPD. METHODS: The Calgary Area Streptococcus pneumoniae Epidemiology Research (CASPER) study collects clinical and laboratory data on all IPD cases in Calgary, Alberta. Analysis was performed on data from 2000 to 2010 comparing ST19A and non-ST19A IPD cases. Adjusted linear and logistic regression models were used to examine outcomes of duration of appropriate intravenous antibiotic therapy and intensive care unit admission, respectively. RESULTS: ST19A tended to cause disease in younger patients. ST19A isolates were more often multidrug resistant (19% versus 0.3%; P<0.001). Adjusted logistic regression showed no difference in intensive care unit admission between ST19A and non-ST19A IPD cases (OR 1.4 [95% CI 0.8 to 2.7]). An adjusted linear regression model showed patients <18 years of age with a diagnosis of bacteremia and no risk factors infected with ST19A were, on average, treated with antibiotics 1.4 times (95% CI 1.1 to 1.9) as long as patients with non-19A IPD and the same baseline characteristics. DISCUSSION: ST19A IPD was associated with an increase in average time on antibiotics. Although many of the infecting strains of ST19A were within the threshold for susceptibility, they may be sufficiently resilient to require a longer duration of antibiotic therapy or higher dose to clear the infection. CONCLUSIONS: ST19A is more common in younger individuals, is more antibiotic resistant and may require longer average treatment duration.
HISTORIQUE: Le Streptoccocus pneumoniae du sérotype 19A (ST19A) est devenu une cause importante de pneumococcie invasive (PI) depuis l'introduction du vaccin conjugué. OBJECTIF: Examiner la gravité et les issues de la PI ST19A par rapport aux PI non ST19A. MÉTHODOLOGIE: L'étude CASPER de recherche épidémiologique sur le Streptococcus pneumoniae dans la région de Calgary s'intéresse à la collecte de données cliniques et de données de laboratoire sur tous les cas de PI à Calgary, en Alberta. Les chercheurs ont analysé les don-nées de 2000 à 2010 pour comparer les cas de PI ST19A aux cas de PI non ST19A. Ils ont utilisé des modèles de régression linéaire et logistique ajustés pour examiner les résultats de la durée d'une antibiothérapie intraveineuse pertinente et de l'hospitalisation à l'unité de soins intensifs, respectivement. RÉSULTATS: Le ST19A avait tendance à susciter la maladie chez des patients plus jeunes. Les isolats de ST19A étaient plus souvent multi-résistants (19 % par rapport à 0,3 %; P<0,001). La régression logistique ajustée ne démontrait aucune différence dans les hospitalisations aux soins intensifs des cas de PI ST19A et des cas de PI non ST19A (RC 1,4 [95 % IC 0,8 à 2,7]). Un modèle de régression linéaire ajusté a révélé que les patients de moins de 18 ans chez qui on avait diagnostiqué une bactériémie, mais qui n'avaient pas de facteurs de risque et qui étaient infectés par le ST19A, étaient traités en moyenne 1,4 fois plus longtemps (95 % IC 1,1 à 1,9) que ceux qui étaient atteints d'une PI non ST19A et qui présentaient les mêmes caractéristiques de départ. EXPOSÉ: La PI ST19A s'associait à une période moyenne d'antibiothérapie plus longue. Même si bon nombre de souches infectieuses du ST19A se situaient dans le seuil de susceptibilité, elles sont peut-être assez résilientes pour qu'une antibiothérapie plus longue ou à plus forte dose puisse éliminer l'infection. CONCLUSIONS: Le ST19A est plus courant chez les plus jeunes, résiste davantage aux antibiotiques et a peut-être besoin d'être traité pendant une période moyenne plus longue.
RESUMEN
BACKGROUND: We previously reported serotype-specific trends in pneumococcal nasopharyngeal colonization soon after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in mid-2002. Our current aim is to describe later trends after PCV7 and early trends after PCV13 vaccine introduction in 2010. METHODS: The Calgary Area Streptococcus pneumoniae Epidemiology Research team conducted 10 point-prevalence surveys of pneumococcal nasopharyngeal colonization in healthy children aged 12 and 18 months and 4.5 years biannually from 2003 to 2005 (previously reported) and annually in 2006, 2010, 2011 and 2012. RESULTS: For surveys conducted during 2010-2012, the proportion colonized was 13.2% compared with 19.9% in surveys conducted during 2003-2006 (P < 0.001). Vaccination with 2 or more doses of PCV7 or PCV13, older age and recent antibiotic use reduced the odds of colonization with any pneumococcus. By 2012, 94% of all isolates were nonvaccine serotypes with 11A, 15A/B/C, 22F, 23A/B and 35B/F representing 75% of all isolates. CONCLUSIONS: Pneumococcal nasopharyngeal colonization has changed profoundly since the introduction of conjugate vaccines and overall colonization by pneumococcus has declined in recent years. By 2012, nonvaccine serotypes have nearly completely replaced vaccine serotypes. The impact on clinical disease remains to be seen.