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Bacterial load of pneumococcal serotypes correlates with their prevalence and multiple serotypes is associated with acute respiratory infections among children less than 5 years of age.


ABSTRACT: BACKGROUND: Among pneumococcal serotypes, some serotypes are more prevalent in the nasopharynx than others; determining factors for higher prevalence remain to be fully explored. As non-vaccine serotypes have emerged after the introduction of 7-valent conjugate vaccines, study of serotype specific epidemiology is in need. When two or more serotypes co-colonize, they evolve rapidly to defend host's immune responses; however, a clear association of co-colonization with a clinical outcome is lacking. METHODS: Children less than 5 years old who were admitted to hospital due to acute respiratory infections (ARI) (n?=?595) and healthy children (n?=?350) were recruited. Carriage of pneumococcus was determined by culture and lytA PCR in the nasopharyngeal samples. Serotype/serogroup detection and its quantification were done by the nanofluidic real time PCR system. Spearman's correlation and logistic regression were used to examine a correlation of serotype/serogroup specific bacterial load with its prevalence and an association of co-colonization with ARI respectively. RESULTS: Serotype/serogroup specific bacterial load was correlated with its prevalence, both in ARI cases (Spearman's rho?=?0.44, n?=?186; P<0.0001) and healthy children (Spearman's rho?=?0.41, n?=?115; P<0.0001). The prevalence of multiple serotypes was more common in ARI cases than in healthy children (18.5% vs 7.1%; aOR 2.92, 95% CI: 1.27-6.71; P?=?0.01). The dominant serotype in the co-colonization had a 2 log10 higher bacterial load than the subdominant serotype, both in ARI cases (P<0.001) and healthy children (P<0.05). CONCLUSIONS: High bacterial load in the nasopharynx may help transmit pneumococci among hosts, and increase the chance of successful acquisition and colonization. Co-colonization of multiple serotypes of pneumococci is linked with ARI, which infers the interactions of multiple serotypes may increase their pathogenicity; however, they may compete for growth in number.

SUBMITTER: Dhoubhadel BG 

PROVIDER: S-EPMC4216008 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Bacterial load of pneumococcal serotypes correlates with their prevalence and multiple serotypes is associated with acute respiratory infections among children less than 5 years of age.

Dhoubhadel Bhim Gopal BG   Yasunami Michio M   Nguyen Hien Anh Thi HA   Suzuki Motoi M   Vu Thu Huong TH   Thi Thuy Nguyen Ai A   Dang Duc Anh DA   Yoshida Lay-Myint LM   Ariyoshi Koya K  

PloS one 20141031 10


<h4>Background</h4>Among pneumococcal serotypes, some serotypes are more prevalent in the nasopharynx than others; determining factors for higher prevalence remain to be fully explored. As non-vaccine serotypes have emerged after the introduction of 7-valent conjugate vaccines, study of serotype specific epidemiology is in need. When two or more serotypes co-colonize, they evolve rapidly to defend host's immune responses; however, a clear association of co-colonization with a clinical outcome is  ...[more]

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