Abstract
Since Streptococcus pneumoniae transmits through droplet spread, this respiratory tract pathogen may be able to survive in saliva. Here, we show that saliva supports survival of clinically relevant S. pneumoniae strains for more than 24 h in a capsule-independent manner. Moreover, saliva induced growth of S. pneumoniae in growth-permissive conditions, suggesting that S. pneumoniae is well adapted for uptake of nutrients from this bodily fluid. By using Tn-seq, a method for genome-wide negative selection screening, we identified 147 genes potentially required for growth and survival of S. pneumoniae in saliva, among which genes predicted to be involved in cell envelope biosynthesis, cell transport, amino acid metabolism, and stress response predominated. The Tn-seq findings were validated by testing a panel of directed gene deletion mutants for their ability to survive in saliva under two testing conditions: at room temperature without CO2, representing transmission, and at 37°C with CO2, representing in-host carriage. These validation experiments confirmed that the plsX gene and the amiACDEF and aroDEBC operons, involved in respectively fatty acid metabolism, oligopeptide transport, and biosynthesis of aromatic amino acids play an important role in the growth and survival of S. pneumoniae in saliva at 37°C. In conclusion, this study shows that S. pneumoniae is well-adapted for growth and survival in human saliva and provides a genome-wide list of genes potentially involved in adaptation. This notion supports earlier evidence that S. pneumoniae can use human saliva as a vector for transmission.
Highlights
Streptococcus pneumoniae is the most common bacterial etiology of community-acquired pneumonia in all ages, and can cause outbreaks in closed settings
Saliva concentration influences S. pneumoniae growth and survival In order to test if S. pneumoniae can survive in human saliva, 104 colony forming units (CFU) ml21 of strain Spain9V-3 (SP195) were incubated with 100%, 50%, 25%, 12.5%, 6.25% and 0% saliva in phosphate-buffered saline (PBS)
At room temperature (RT) without CO2, S. pneumoniae survived in 100% saliva and no significant differences in viable bacterial counts between different saliva concentrations were observed at t = 4 h
Summary
Streptococcus pneumoniae is the most common bacterial etiology of community-acquired pneumonia in all ages, and can cause outbreaks in closed settings. The most common manifestations of pneumococcal disease include sinusitis, otitis media, pneumonia and sepsis. Immunoglobulin G (IgG) and secretory IgA antibodies directed against capsular polysaccharides and surface-associated proteins have been observed in saliva of children in response to colonization with S. pneumoniae [2,3]. The presence of antipneumococcal IgA antibodies in saliva has been associated with a lowered risk of pneumococcal acute otitis media (AOM), while the serum IgG antibody level does not seem to be associated with AOM risk [4]. This suggests that the presence of S. pneumoniae in saliva is associated with the development of local pneumococcal disease
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
