Editing Streptococcus pneumoniae (section)

{{Short description|Species of bacterium}}
{{cs1 config|name-list-style=vanc}}
{{Speciesbox
| image = Pneumococcus_CDC_PHIL_ID1003.jpg
| image_caption = ''S. pneumoniae'' in spinal fluid. FA stain (digitally colored).
| genus = Streptococcus
| species = pneumoniae
| authority = (Klein 1884) Chester 1901
}}

'''''Streptococcus pneumoniae''''', or '''pneumococcus''', is a [[Gram-positive]], spherical bacteria, [[hemolysis (microbiology)|alpha-hemolytic]] member of the [[genus]] ''[[Streptococcus]]''.<ref name=Sherris>{{cite book |veditors = Ryan KJ, Ray CG |title = Sherris Medical Microbiology |publisher = McGraw Hill |year = 2004 |isbn = 978-0-8385-8529-0 }}</ref> ''S. pneumoniae'' cells are usually found in pairs ([[diplococci]]) and  do not form [[Bacterial morphological plasticity|spores]] and are non motile.<ref>{{Cite web|url=https://microbewiki.kenyon.edu/index.php/Streptococcus_pneumoniae|title=Streptococcus pneumoniae|website=microbewiki.kenyon.edu|access-date=2017-10-24}}</ref> As a significant human [[pathogenic bacterium]] ''S. pneumoniae'' was recognized as a major cause of [[pneumonia]] in the late 19th century, and is the subject of many [[humoral immunity]] studies.{{citation needed|date=June 2022}}

''Streptococcus pneumoniae'' resides asymptomatically in healthy carriers typically colonizing the respiratory tract, sinuses, and [[nasopharynx|nasal cavity]]. However, in susceptible individuals with [[immunocompromised|weaker immune systems]], such as the elderly and young children, the bacterium may become [[pathogen]]ic and spread to other locations to cause disease. It spreads by  direct person-to-person contact via [[respiratory droplet]]s and by auto inoculation in persons carrying the bacteria in their upper respiratory tracts.<ref>{{cite web |url= https://www.cdc.gov/pneumococcal/clinicians/transmission.html|title= Transmission|website= cdc.org |access-date= 24 Oct 2017 }}</ref> It can be a cause of [[neonatal infection]]s.<ref name="BaucellsMercadal Hally2015">{{cite journal |last1=Baucells |first1=B.J. |last2=Mercadal Hally |first2=M. |last3=Álvarez Sánchez |first3=A.T. |last4=Figueras Aloy |first4=J. |title=Asociaciones de probióticos para la prevención de la enterocolitis necrosante y la reducción de la sepsis tardía y la mortalidad neonatal en recién nacidos pretérmino de menos de 1.500g: una revisión sistemática |journal=Anales de Pediatría |volume=85 |issue=5 |pages=247–255 |year=2015 |issn=1695-4033 |doi=10.1016/j.anpedi.2015.07.038|pmid=26611880 |doi-access=free }}</ref>

''Streptococcus pneumoniae'' is the main cause of [[community acquired pneumonia]] and [[meningitis]] in children and the elderly,<ref name="NEJM">{{cite journal|last1=van de Beek|first1=Diederik|last2=de Gans|first2=Jan|last3=Tunkel|first3=Allan R.|last4=Wijdicks|first4=Eelco F.M.|title=Community-Acquired Bacterial Meningitis in Adults|journal=New England Journal of Medicine|date=5 January 2006|volume=354|issue=1|pages=44–53|doi=10.1056/NEJMra052116|issn=0028-4793|pmid=16394301}}</ref> and of [[sepsis]] in those infected with [[HIV]]. The organism also causes many types of [[pneumococcal infection]]s other than [[pneumonia]].  These invasive pneumococcal diseases include [[bronchitis]], [[rhinitis]], [[acute sinusitis]], [[otitis media]], [[conjunctivitis]], [[meningitis]], sepsis, [[osteomyelitis]], [[septic arthritis]], [[endocarditis]], [[peritonitis]], [[pericarditis]], [[cellulitis]], and [[brain abscess]].<ref name="Siemieniuk 2011">{{cite journal|last=Siemieniuk|first=Reed A.C.|author2= Gregson, Dan B. |author3=Gill, M. John |title=The persisting burden of invasive pneumococcal disease in HIV patients: an observational cohort study|journal=BMC Infectious Diseases|date=Nov 2011|volume=11|doi=10.1186/1471-2334-11-314|pmid=22078162|pmc=3226630|pages=314 |doi-access=free }}</ref>
[[File:Streptococcus pneumoniae on agar plates.jpg|thumb|238x238px|S.pneumoniae growth on blood agar.]]
''Streptococcus pneumoniae'' can be differentiated from the [[viridans streptococci]], some of which are also [[hemolysis (microbiology)|alpha-hemolytic]], using an [[optochin]] test, as ''S. pneumoniae'' is optochin-sensitive. ''S. pneumoniae'' can also be distinguished based on its sensitivity to [[lysis]] by [[bile]], the so-called "bile solubility test". The [[bacterial capsule|encapsulated]], Gram-positive, [[coccus|coccoid]] bacteria have a distinctive morphology on Gram stain, [[scalpel|lancet]]-shaped diplococci. They have a [[polysaccharide]] capsule that acts as a [[virulence factor]] for the organism; more than 100 different [[serotype]]s are known<ref>{{cite journal |last1=Ganaie |first1=F.A. |last2=Beall |first2=B.W. |last3=Yu |first3=J. |last4=van der Linden |first4=M. |last5=McGee |first5=L. |last6=Satzke |first6=C. |last7=Manna |first7=S. |last8=Lo |first8=S.W. |last9=Bentley |first9=S.D. |last10=Ravenscroft |first10=N. |last11=Nahm |first11=M.H. |title=Update on the evolving landscape of pneumococcal capsule types: new discoveries and way forward |journal=Clinical Microbiology Reviews |date=January 29, 2025 |volume=8 |issue=1 |pages=e0017524 |doi=10.1128/cmr.00175-24 |pmid=39878373|pmc=11905375 |pmc-embargo-date=January 29, 2026 }}</ref>
, and these types differ in [[virulence]], [[prevalence]], and extent of [[drug resistance]].

The capsular polysaccharide (CPS) serves as a critical defense mechanism against the host immune system. It composes the outermost layer of encapsulated strains of ''S. pneumoniae'' and is commonly attached to the peptidoglycan of the cell wall.<ref>{{Cite journal |last1=Paton |first1=James C. |last2=Trappetti |first2=Claudia |date=2019-04-12 |editor-last=Fischetti |editor-first=Vincent A. |editor2-last=Novick |editor2-first=Richard P. |editor3-last=Ferretti |editor3-first=Joseph J. |editor4-last=Portnoy |editor4-first=Daniel A. |editor5-last=Braunstein |editor5-first=Miriam |editor6-last=Rood |editor6-first=Julian I. |title=Streptococcus pneumoniae Capsular Polysaccharide |journal=Microbiology Spectrum |language=en |volume=7 |issue=2 |doi=10.1128/microbiolspec.GPP3-0019-2018 |pmid=30977464 |issn=2165-0497|pmc=11590643 }}</ref> It consists of a viscous substance derived from a high-molecular-weight polymer composed of repeating oligosaccharide units linked by covalent bonds to the cell wall. The virulence and invasiveness of various strains of ''S. pneumoniae'' vary according to their serotypes, determined by their chemical composition and the quantity of CPS they produce. Variations among different ''S. pneumoniae'' strains significantly influence [[Pathogenesis#:~:text=In pathology, pathogenesis is the,to its progression and maintenance.|pathogenesis]], determining bacterial survival and likelihood of causing invasive disease.<ref>{{Cite journal |last1=Morais |first1=Victor |last2=Dee |first2=Valerie |last3=Suárez |first3=Norma |date=2018-10-12 |title=Purification of Capsular Polysaccharides of Streptococcus pneumoniae: Traditional and New Methods |journal=Frontiers in Bioengineering and Biotechnology |volume=6 |page=145 |doi=10.3389/fbioe.2018.00145 |doi-access=free |issn=2296-4185 |pmc=6194195 |pmid=30370268}}</ref> Additionally, the CPS inhibits [[phagocytosis]] by preventing [[granulocyte]]s' access to the cell wall.<ref>{{Citation |last1=Dion |first1=Christopher F. |title=Streptococcus pneumoniae |date=2024 |work=StatPearls |url=http://www.ncbi.nlm.nih.gov/books/NBK470537/ |access-date=2024-04-15 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29261971 |last2=Ashurst |first2=John V.}}</ref>