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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 BG, Yasunami M, Nguyen HA, Suzuki M, Vu TH, Thi Thuy Nguyen A, Dang DA, Yoshida LM, Ariyoshi K - PLoS ONE (2014)

Bottom Line: 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).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.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.

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.

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Distribution of serotypes/serogroups of pneumococcus in ARI cases and healthy children.Thirteen different serotypes/serogroups were detected; DNA samples which were positive for lytA (pneumococcus positive), but negative for tested 29 serotypes/serogroups were assigned as non-typeable (NT). Prevalence of each serotype/serogroup was calculated as proportion of total number of a serotype/serogroup to the total number of the lytA positive samples. Serotype/serogroup of ARI cases and healthy children were plotted in red and blue respectively. Proportion of serotype/serogroup covered by 13-valent conjugated vaccine (PCV13) was 74% in ARI cases and 55% in healthy children.
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pone-0110777-g002: Distribution of serotypes/serogroups of pneumococcus in ARI cases and healthy children.Thirteen different serotypes/serogroups were detected; DNA samples which were positive for lytA (pneumococcus positive), but negative for tested 29 serotypes/serogroups were assigned as non-typeable (NT). Prevalence of each serotype/serogroup was calculated as proportion of total number of a serotype/serogroup to the total number of the lytA positive samples. Serotype/serogroup of ARI cases and healthy children were plotted in red and blue respectively. Proportion of serotype/serogroup covered by 13-valent conjugated vaccine (PCV13) was 74% in ARI cases and 55% in healthy children.

Mentions: Pneumococcal carriage rate was 32.6% (194/595) in ARI cases and 40% (140/350) in healthy children (figure 1). The proportion of typeable serotypes in ARI cases and healthy children were 95.9% (186/194) and 82.1% (115/140) respectively. Thirteen serotypes/serogroups of pneumococcus were detected in ARI cases and healthy children (figure 2). Serotypes/serogroups 19F, 6A/6B, 23F and 6C/6D were more prevalent in hospitalized ARI cases while serotypes/serogroups 14, 6A/6B, 19F, 15B/15C, 11 and non-typeables (NT) were common in healthy children. The proportion of serotypes/serogroups covered by pneumococcal conjugate vaccines: 7-valent (PCV7), 10-valent (PCV10) and 13-valent (PCV13) were approximately equal to one another, which was about 74% in ARI cases and 55% in healthy children (this was an approximate estimation as a serogroup was treated as a serotype as required).


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 BG, Yasunami M, Nguyen HA, Suzuki M, Vu TH, Thi Thuy Nguyen A, Dang DA, Yoshida LM, Ariyoshi K - PLoS ONE (2014)

Distribution of serotypes/serogroups of pneumococcus in ARI cases and healthy children.Thirteen different serotypes/serogroups were detected; DNA samples which were positive for lytA (pneumococcus positive), but negative for tested 29 serotypes/serogroups were assigned as non-typeable (NT). Prevalence of each serotype/serogroup was calculated as proportion of total number of a serotype/serogroup to the total number of the lytA positive samples. Serotype/serogroup of ARI cases and healthy children were plotted in red and blue respectively. Proportion of serotype/serogroup covered by 13-valent conjugated vaccine (PCV13) was 74% in ARI cases and 55% in healthy children.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4216008&req=5

pone-0110777-g002: Distribution of serotypes/serogroups of pneumococcus in ARI cases and healthy children.Thirteen different serotypes/serogroups were detected; DNA samples which were positive for lytA (pneumococcus positive), but negative for tested 29 serotypes/serogroups were assigned as non-typeable (NT). Prevalence of each serotype/serogroup was calculated as proportion of total number of a serotype/serogroup to the total number of the lytA positive samples. Serotype/serogroup of ARI cases and healthy children were plotted in red and blue respectively. Proportion of serotype/serogroup covered by 13-valent conjugated vaccine (PCV13) was 74% in ARI cases and 55% in healthy children.
Mentions: Pneumococcal carriage rate was 32.6% (194/595) in ARI cases and 40% (140/350) in healthy children (figure 1). The proportion of typeable serotypes in ARI cases and healthy children were 95.9% (186/194) and 82.1% (115/140) respectively. Thirteen serotypes/serogroups of pneumococcus were detected in ARI cases and healthy children (figure 2). Serotypes/serogroups 19F, 6A/6B, 23F and 6C/6D were more prevalent in hospitalized ARI cases while serotypes/serogroups 14, 6A/6B, 19F, 15B/15C, 11 and non-typeables (NT) were common in healthy children. The proportion of serotypes/serogroups covered by pneumococcal conjugate vaccines: 7-valent (PCV7), 10-valent (PCV10) and 13-valent (PCV13) were approximately equal to one another, which was about 74% in ARI cases and 55% in healthy children (this was an approximate estimation as a serogroup was treated as a serotype as required).

Bottom Line: 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).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.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.

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.

Show MeSH
Related in: MedlinePlus