An easy method for detection of nasopharyngeal carriage of multiple Streptococcus pneumoniae serotypes

In this paper, a simplified method for detection of pneumococcal carriage and for revealing the presence of several serotypes in a nasopharyngeal sample is evaluated. Enrichment broth was used for transportation and for the initial culturing of samples. All specimens were examined directly by the capsular reaction test for the presence of any of the 91 known pneumococcal serotypes. Sub-culturing on blood agar was used for isolation of the pneumococcal strains detected in the primary broth culture. A total of 693 nasopharyngeal swabs were obtained among children, their parents and employees in day care centres. Pneumococci were observed in 363 samples and 36 of these (9.9%) contained more than one serotype (multiple carriages). Two persons carried 3 different serotypes simultaneously. A significant increase in the positive sampling rate (5.8%) was achieved by using the simplified method compared to conventional streaking of the swabs directly on blood agar (p<0.0001).