Modified sequential multiplex PCR for determining capsular serotypes of invasive pneumococci recovered from Seville

The heptavalent pneumococcal vaccine’s introduction resulted in a decline in invasive disease caused by Streptococcus pneumoniae, but was accompanied by an increase in non-vaccine serotypes. We evaluated a modified scheme of the sequential multiplex PCRs adapted to the prevalence of serotypes in Seville (Spain) for determining capsular serotypes of S. pneumoniae invasive clinical isolates. In adults, the modified scheme allowed us to type 73% with the first three reactions, and 92% with two additional PCRs. In paediatric patients, it allowed us to type 73.5% with the first three reactions, and 90% with the two additional PCRs. The multiplex PCR approach was successfully adapted to target the serotypes most prevalent in Seville.