Characterization of Streptococcus pneumoniae serotype 19F-variants occurring in Brazil uncovers a predominant lineage that can lead to misinterpretation in capsular typing.

Background: Streptococcus pneumoniae (S. pneumoniae) of serogroup 19 are mainly represented by serotypes 19A and 19F, which are associated with antimicrobial resistance and disease. The wzy gene, a component of the pneumococcal capsular locus, is the target to differentiate serotypes 19A and 19F by PCR-based capsular typing. In the last decade, allelic variants of the wzy gene have been described, leading to misinterpretation of capsular typing results.

Methods: A collection of 154 serotype 19F S. pneumoniae strains recovered from carriage and disease in Brazil was evaluated to identify and characterize wzy variant isolates.

Results: Eleven (7%) wzy variant isolates were detected and identified as belonging to ST810 (n = 10) or ST13673 (n = 1; single-locus variant of ST810). They were mostly recovered from diseased patients, susceptible to the antimicrobial agents tested (except for one multidrug-resistant strain) and did not harbor pili genes. Sequences of the wzy gene of these variants were identical to each other and to those previously described in Brazil, but slightly different from wzy variants identified in other countries.

Conclusion: This study indicated that wzy variants present a geographically driven distribution and was the first to uncover phenotypic and genetic features of a wzy variant lineage occurring in Brazil since 1989.