In vitro growth of pneumococcal isolates representing 23 different serotypes

BACKGROUND: Although there are established methodologies for pneumococcal carriage studies, recent studies have extended these by conducting a culture amplification step prior to pneumococcal identification or serotyping. However, few data are available comparing the growth of different serotypes. FINDINGS: We compared the growth of individual isolates representing 23 serotypes in serum broth, and Todd-Hewitt broth from four different manufacturers. Following overnight incubation of low inocula, there were differences in the final growth densities of individual isolates. These can be minimised with the use of optimal media. CONCLUSIONS: These data caution against using broth culture amplification of nasopharyngeal samples for some applications.