Increase of serotype 8, ST53 clone, as the prevalent strain of Streptococcus pneumoniae causing invasive disease in Madrid, Spain (2012-2015).
INTRODUCTION
In recent years, Streptococcus pneumoniae serotype 8 has become the most prevalent cause of invasive pneumococcal disease (IPD) in Madrid, Spain. The objective of this study was to characterize the invasive clones of S. pneumoniae serotype 8 in Madrid over the 2012-2015 period.


METHODS
From January 2012 to December 2015, a total of 1543 invasive isolates were studied. Serotyping was carried out by Pneumotest-Latex agglutination and Quellung reaction. Susceptibilities to penicillin, erythromycin and levofloxacin were determined by the Etest®. All serotype 8 strains were typed by multilocus sequence typing (MLST) and by pulsed-field gel electrophoresis (PFGE).


RESULTS
Two hundred and forty-eight (248) serotype 8 strains were detected (16.1%) and 243 of them were available for molecular typing. Nine sequence types (STs) by MLST (8-ST53, 8-ST63, 8-ST404, 8-ST1107, 8-ST989, 8-ST1110, 8-ST2231, 8-ST3544 and 8-ST4301), and nine PFGE profiles were identified (one corresponding to each ST). The 8-ST53 clone was the most widespread, and increased from 53.8% among all serotype 8 isolates in 2012, to 90.1% in 2015. In contrast, the 8-ST63 clone, resistant to levofloxacin and erythromycin, decreased from 30.8%, among all serotype 8 strains in 2012, to 5.0% in 2015.


CONCLUSIONS
The increase in our region of S. pneumoniae serotype 8, not included in conjugated vaccines, occurred at the expense of the 8-ST53 clone. On the contrary, the 8-ST63 clone decreased. Since clone 8-ST63 has the theoretical advantage of its levofloxacin-erythromycin resistance in comparison to 8-ST53, the predominance of 8-ST53 over 8-ST63 is striking.
['Sanz|Juan Carlos|JC|', 'Rodríguez-Avial|Iciar|I|', 'Ríos|Esther|E|', 'García-Comas|Luis|L|', 'Ordobás|María|M|', 'Cercenado|Emilia|E|']
D000900:Anti-Bacterial Agents D002999:Clone Cells D006801:Humans D008826:Microbial Sensitivity Tests D058885:Multilocus Sequence Typing D011008:Pneumococcal Infections D065288:Serogroup D013030:Spain D013296:Streptococcus pneumoniae
Serotype 8 Streptococcus pneumoniae MLST clones Serotipo 8