| Summary: | <i>Streptococcus pneumoniae</i> shows more than 90 capsular serotypes that can be distinguished by their reactivity against antisera. The main objective of this work was the development of a molecular method for serotyping without the use of antisera. A computer program containing an algorithm was used to search in a database for potentially useful enzymes for Restriction Fragment Length Polymorphism-RFLP typing, in order to maximize the discrimination between different serotypes. DNA sequences of 90 serotypes for the region between <i>dex</i>B and <i>ali</i>A genes were compiled, and a computer screening of restriction enzymes was performed. The<i> </i><i>wzg</i><i>−</i><i>wzh</i><i>−</i><i>wzd</i><i>−</i><i>wze</i><i> </i>region and <i>Sse</i>9I restriction predicted unique PCR-RFLP patterns for 39 serotypes and eight serogroups. A second restriction enzyme resolved fragment specific patterns for 25 serotypes. The method was tested with 98 serotype-unknown clinical isolates. PCR-RFLP analysis deduced correct serotypes that were confirmed by Quellung reaction for 78.5% of the isolates.
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