A study sample of 7,010 episodes of invasive Streptococcus pneumoniae disease was obtained by combining 13 existing datasets. Disease episodes due to each of 12 pneumococcal serogroups (1, 3-9, 14, 18, 19, and 23) were then compared with episodes in a constant internal control group to describe serogroup-specific variations in disease frequency by age, sex, and geographic origin. The results are presented as odds ratios (with 95% confidence intervals) derived by logistic regression, with adjustment for the major confounders, including dataset of origin. Variation in the male:female ratios between serogroups is small, suggesting that capsular characteristics are an unlikely explanation for the male preference of S. pneumoniae. Serogroups associated with higher nasopharyngeal prevalence (e.g., 19 and 24) are relatively more common in Europe and North American, while the invasive serotypes 1 and 5 are much more common in South America. The custom of reporting serogroup frequencies in two age groups, children and adults, conceals much of the variation in the age distributions across the whole span of life. The reduction of risk associated with serogroups 6, 14, 18, 19, and 23 beyond childhood follows different gradients, being most abrupt in serogroups 14 and most gradual in serogroup 18. The relative risk of disease with serotype 1 declines steadily throughout life, while with serotypes 3 and 8 it increases over middle age. Serogroups 7 and 23 are found unusually frequently in the third decade of life. Because of the wide differences in the epidemiology of individual serogroups of S. pneumoniae, it is questionable whether pneumococcal infection should continue to be classified as a single disease entity.

Disease rates are high among indigenous persons in Arctic countries, and PCV7 has resulted in decreased rates in North American children.

13 Gustafson JE, Wilkinson BJ. Lower autolytic activity in a homogeneous methicillin-resistant Staphylococcus aureus strain compared to derived heterogeneous-resistant and susceptible strains.

No abstract

were serotyped, their susceptibilities to antimicrobial agents were determined, and the laboratory data were correlated with the clinical information. The distribution pattern of the serogroups and serotypes was similar to that observed previously in Quebec and to that in other parts of Canada and in the United States. No regional variation was observed. The distribution of serogroups and serotypes was different in pediatric patients (<18 years old) when compared with that of adults (P < 0.001). Overall, 94% of the strains were represented in 23-valent vaccine. The total mortality rate was 12.8% and increased with age: 1.6% in pediatric patients, 14.8% in patients 18 to 64 years old, and 31% in those .65 years old (P < 0.001). In patients 18 to 64 years old, the mortality rate was higher when an underlying condition that could have justified prior vaccination was present (P = 0.008). In patients .65 years old, the mortality rates were similar in those with and those without underlying conditions, suggesting that vaccine use in all patients .65 years old might be appropriate. Only six patients had received pneumococcal vaccine before infection. Only 15 strains (3.2%) were moderately susceptible or resistant to one or more of the antimicrobial agents tested. Six strains were moderately susceptible to penicillin G, and none was fully resistant.