Streptococcus mitis Expressing Pneumococcal Serotype 1 Capsule

• Published in: Scientific reports 2018-12, Vol.8 (1), p.17959-9, Article 17959
• Main Authors: Lessa, Fernanda C., Milucky, Jennifer, Rouphael, Nadine G., Bennett, Nancy M., Talbot, H. Keipp, Harrison, Lee H., Farley, Monica M., Walston, Jeremy, Pimenta, Fabiana, Gertz, Robert E., Rajam, Gowrisankar, Carvalho, Maria da Gloria, Beall, Bernard, Whitney, Cynthia G.
• Format: Article
• Language: English
• Subjects: 101/1; 45; 45/23; 45/77; 631/326; 692/699/255; Bacterial Capsules - genetics; Bacterial Capsules - immunology; Capsular polysaccharides; Cross Reactions; Cross-Sectional Studies; Gene Expression; Gene Order; Genes, Bacterial; Genomes; Humanities and Social Sciences; Humans; Meningitis; multidisciplinary; Outbreaks; Phylogeny; Pneumococcal Infections - immunology; Pneumococcal Infections - microbiology; Pneumococcal Infections - prevention & control; Polymerase chain reaction; Respiratory tract; Science; Science (multidisciplinary); Serogroup; Streptococcus; Streptococcus infections; Streptococcus mitis - classification; Streptococcus mitis - genetics; Streptococcus pneumoniae - classification; Streptococcus pneumoniae - genetics; Vaccines; Virulence Factors
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-35921-3

Streptococcus pneumoniae’s polysaccharide capsule is an important virulence factor; vaccine-induced immunity to specific capsular polysaccharide effectively prevents disease. Serotype 1 S . pneumoniae is rarely found in healthy persons, but is highly invasive and a common cause of meningitis outbreaks and invasive disease outside of the United States. Here we show that genes for polysaccharide capsule similar to those expressed by pneumococci were commonly detected by polymerase chain reaction among upper respiratory tract samples from older US adults not carrying pneumococci. Serotype 1-specific genes were predominantly detected. In five oropharyngeal samples tested, serotype 1 gene belonging to S . mitis expressed capsules immunologically indistinct from pneumococcal capsules. Whole genome sequencing revealed three distinct S . mitis clones, each representing a cps1 operon highly similar to the pneumococcal cps1 reference operon. These findings raise important questions about the contribution of commensal streptococci to natural immunity against pneumococci, a leading cause of mortality worldwide.