Emerging, Non-PCV13 Serotypes 11A and 35B of Streptococcus pneumoniae Show High Potential for Biofilm Formation In Vitro.
BACKGROUND
Since the use of pneumococcal conjugate vaccines PCV7 and PCV13 in children became widespread, invasive pneumococcal disease (IPD) has dramatically decreased. Nevertheless, there has been a rise in incidence of Streptococcus pneumoniae non-vaccine serotypes (NVT) colonising the human nasopharynx. Nasopharyngeal colonisation, an essential step in the development of S. pneumoniae-induced IPD, is associated with biofilm formation. Although the capsule is the main pneumococcal virulence factor, the formation of pneumococcal biofilms might, in fact, be limited by the presence of capsular polysaccharide (CPS).


RESULTS
We used clinical isolates of 16 emerging, non-PCV13 serotypes as well as isogenic transformants of the same serotypes. The biofilm formation capacity of isogenic transformants expressing CPSs from NVT was evaluated in vitro to ascertain whether this trait can be used to predict the emergence of NVT. Fourteen out of 16 NVT analysed were not good biofilm formers, presumably because of the presence of CPS. In contrast, serotypes 11A and 35B formed ≥45% of the biofilm produced by the non-encapsulated M11 strain.


CONCLUSIONS
This study suggest that emerging, NVT serotypes 11A and 35B deserve a close surveillance.
Centro de Investigaciones Biológicas, CSIC, Madrid, Spain; CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain.
Mirian
M
Domenech
Centro de Investigaciones Biológicas, CSIC, Madrid, Spain.
Diana
D
Damián
CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain; Hospital Universitari de Bellvitge-Universitat de Barcelona-Fundació Privada Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain.
Carmen
C
Ardanuy
CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain; Hospital Universitari de Bellvitge-Universitat de Barcelona-Fundació Privada Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain.
Josefina
J
Liñares
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
Asunción
A
Fenoll
Centro de Investigaciones Biológicas, CSIC, Madrid, Spain; CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain.
Ernesto
E
García
D018441:Biofilms / Q000254:growth & development*; D022242:Pneumococcal Vaccines; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000378:metabolism; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000235:genetics / Q000254:growth & development*
D022242:Pneumococcal Vaccines; D011135:Polysaccharides, Bacterial