Editing Infective endocarditis (section)

===Bacterial===
''[[Staphylococcus aureus]]'' is the leading cause of infective endocarditis in most parts of the world and is responsible for about 31% of cases.<ref name="Hubers2020"/> Staphylococcus aureus is the most common cause of endocarditis in people who use intravenous drugs.<ref>{{cite book | vauthors = Chan KL, Embil JM |title=Endocarditis: Diagnosis and Management |date=2016 |publisher=Springer |isbn=978-3-319-27784-4 |page=39 |url=https://books.google.com/books?id=WNCzCwAAQBAJ&pg=PA39 |language=en}}</ref> [[Viridans streptococci]] and [[Enterococcus|Enterococci]] are the second and third most common organisms responsible for infective endocarditis.<ref name="Hubers2020"/> Viridans streptococci are a common cause of infective endocarditis in South America. Other ''Streptococci''  are also a frequent cause. Infective endocarditis due to ''[[Streptococcus bovis]]'' occurs more commonly in Europe than in North America.<ref name="Hubers2020"/> [[HACEK]] group of bacteria are also rare causes of infective endocarditis in North America.<ref name=Murdoch>{{cite journal | vauthors = Murdoch DR, Corey GR, Hoen B, Miró JM, Fowler VG, Bayer AS, Karchmer AW, Olaison L, Pappas PA, Moreillon P, Chambers ST, Chu VH, Falcó V, Holland DJ, Jones P, Klein JL, Raymond NJ, Read KM, Tripodi MF, Utili R, Wang A, Woods CW, Cabell CH | title = Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study | journal = Archives of Internal Medicine | volume = 169 | issue = 5 | pages = 463–73 | date = March 2009 | pmid = 19273776 | pmc = 3625651 | doi = 10.1001/archinternmed.2008.603 }}</ref>

The viridans group includes ''S. oralis'', ''S. mitis'', ''S. sanguis'', ''S. gordonii'' and ''S. parasanguis''. The primary habitats for these organisms are the oral cavity and upper respiratory tract.<ref name="Bagg_2006">{{Cite book|title=Essentials of microbiology for dental students| vauthors = Bagg J |date=2006|publisher=Oxford University Press|isbn=9780198564898|edition=2nd|location=Oxford|oclc=61756542}}</ref> These bacteria are present in the normal oral flora and enter the bloodstream due to disruption of tissues in the mouth when dental surgical procedures are performed (tooth extractions) or genitourinary manipulation. Similarly, HACEK organisms are a group of bacteria that live on the dental gums and can be seen with people who inject drugs who contaminate their needles with saliva. Patients may also have a history of poor dental hygiene or pre-existing valvular disease.<ref>{{EMedicine|med|935|HACEK Group Infections}}</ref>

[[Streptococcus viridans|Viridans]] [[Hemolysis (microbiology)|alpha-hemolytic]] ''[[Streptococcus|streptococci]]'', that are present in the mouth, are the most frequently isolated microorganisms when the infection is acquired in a community setting. In contrast, ''[[Staphylococcal|Staphylococcus]]'' bloodstream infections are frequently acquired in a health care setting where they can enter the bloodstream through procedures that cause breaks in the integrity of skin, such as surgery, catheterization, or during access of long term indwelling catheters or secondary to intravenous injection of recreational drugs.{{citation needed|date=February 2021}}

''Enterococcus'' can enter the bloodstream as a consequence of abnormalities in the gastrointestinal or genitourinary tracts.{{citation needed|date=February 2021}}

Some organisms, when isolated, give valuable clues to the cause, as they tend to be specific.
* ''[[Pseudomonas]]'' species, which are very resilient organisms that thrive in water, may contaminate street drugs that have been contaminated with drinking water. ''[[Pseudomonas aeruginosa|P. aeruginosa]]'' can infect a child through foot punctures, and can cause both endocarditis and [[septic arthritis]].<ref>{{cite web|title=''Pseudomonas aeruginosa'' |date=August 2001 |work=Topics in Infectious Diseases Newsletter |url=http://wordnet.com.au/Products/topics_in_infectious_diseases_Aug01.htm |archive-date=July 24, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080724235537/http://wordnet.com.au/Products/topics_in_infectious_diseases_Aug01.htm }}</ref>
* ''[[Streptococcus bovis|S. bovis]]'' and ''[[Clostridium septicum]]'', which are part of the natural flora of the bowel, are associated with [[colon cancer]]s. When they present as the causative agent in endocarditis, it usually prompts a [[colonoscopy]] to be done immediately due to concerns regarding spread of bacteria from the colon through the bloodstream due to the cancer breaking down the barrier between the inside of the colon (lumen) and the blood vessels which drain the bowel.<ref name=Gold2004>{{cite journal | vauthors = Gold JS, Bayar S, Salem RR | title = Association of Streptococcus bovis bacteremia with colonic neoplasia and extracolonic malignancy | journal = Archives of Surgery | volume = 139 | issue = 7 | pages = 760–5 | date = July 2004 | pmid = 15249410 | doi = 10.1001/archsurg.139.7.760 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Chew SS, Lubowski DZ | title = Clostridium septicum and malignancy | journal = ANZ Journal of Surgery | volume = 71 | issue = 11 | pages = 647–9 | date = November 2001 | pmid = 11736823 | doi = 10.1046/j.1445-1433.2001.02231.x | s2cid = 7571197 }}</ref>
* Less commonly reported bacteria responsible for so called "culture negative endocarditis" include ''[[Bartonella]]'', ''[[Chlamydia psittaci]]'', and ''[[Coxiella (bacterium)|Coxiella]]''.<ref name=Lamas>{{cite journal | vauthors = Lamas CC, Eykyn SJ | title = Blood culture negative endocarditis: analysis of 63 cases presenting over 25 years | journal = Heart | volume = 89 | issue = 3 | pages = 258–62 | date = March 2003 | pmid = 12591823 | pmc = 1767579 | doi = 10.1136/heart.89.3.258 }}</ref> Such bacteria can be identified by serology, culture of the excised valve tissue, sputum, pleural fluid, and emboli, and by polymerase chain reaction or sequencing of bacterial 16S ribosomal RNA.

Multiple case reports of infective endocarditis caused by unusual organisms have been published. ''[[Cutibacterium]]'' spp., which are normal skin flora, have been responsible for infective endocarditis, preferably in patients with prosthetic heart valves, in rare cases leading to death.<ref>{{cite journal | vauthors = Clayton JJ, Baig W, Reynolds GW, Sandoe JA | title = Endocarditis caused by Propionibacterium species: a report of three cases and a review of clinical features and diagnostic difficulties | journal = Journal of Medical Microbiology | volume = 55 | issue = Pt 8 | pages = 981–987 | date = August 2006 | pmid = 16849716 | doi = 10.1099/jmm.0.46613-0 | doi-access = free }}</ref>''[[Tropheryma whipplei]]'' has caused endocarditis without gastrointestinal involvement.<ref>{{cite journal | vauthors = Dreier J, Szabados F, von Herbay A, Kröger T, Kleesiek K | title = Tropheryma whipplei Infection of an acellular porcine heart valve bioprosthesis in a patient who did not have intestinal Whipple's disease | journal = Journal of Clinical Microbiology | volume = 42 | issue = 10 | pages = 4487–93 | date = October 2004 | pmid = 15472298 | pmc = 522317 | doi = 10.1128/JCM.42.10.4487-4493.2004 }}</ref> ''[[Citrobacter koseri]]'' was found in an immunocompetent adult.<ref>{{cite journal | vauthors = Dzeing-Ella A, Szwebel TA, Loubinoux J, Coignard S, Bouvet A, Le Jeunne C, Aslangul E | title = Infective endocarditis due to Citrobacter koseri in an immunocompetent adult | journal = Journal of Clinical Microbiology | volume = 47 | issue = 12 | pages = 4185–6 | date = December 2009 | pmid = 19812281 | pmc = 2786675 | doi = 10.1128/JCM.00957-09 }}</ref> ''Neisseria bacilliformis'' was found in a person with a [[bicuspid aortic valve]].<ref>{{cite journal | vauthors = Masliah-Planchon J, Breton G, Jarlier V, Simon A, Benveniste O, Herson S, Drieux L | title = Endocarditis due to Neisseria bacilliformis in a patient with a bicuspid aortic valve | journal = Journal of Clinical Microbiology | volume = 47 | issue = 6 | pages = 1973–5 | date = June 2009 | pmid = 19386832 | pmc = 2691068 | doi = 10.1128/JCM.00026-09 }}</ref>

====Dental operations====
One in eight cases of infective endocarditis is thought to be caused by S. viridans infection associated with dental procedures such as cleaning or tooth [[Extraction (dental)|extraction]]<ref name="Bagg_2006" />{{Obsolete source|reason=|date=March 2024}}. This was thought to be more clinically significant than it is{{citation needed|date=March 2024}}. However, it is important that a dentist or a dental hygienist be told of any heart problems before commencing treatment. Prophylactic [[antibiotics]] were regularly administered to patients with certain heart conditions as a precaution, although this practice has changed in the US, with new American Heart Association [[Dental antibiotic prophylaxis|guidelines]] released in 2007,<ref name="AHA_2007">{{cite journal | vauthors = Wilson W, Taubert KA, Gewitz M, Lockhart PB, Baddour LM, Levison M, Bolger A, Cabell CH, Takahashi M, Baltimore RS, Newburger JW, Strom BL, Tani LY, Gerber M, Bonow RO, Pallasch T, Shulman ST, Rowley AH, Burns JC, Ferrieri P, Gardner T, Goff D, Durack DT | display-authors = 6 | title = Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group | journal = Circulation | volume = 116 | issue = 15 | pages = 1736–54 | date = October 2007 | pmid = 17446442 | doi = 10.1161/CIRCULATIONAHA.106.183095 | doi-access = free }}</ref> and in the UK as of March 2008 due to new [[National Institute for Health and Care Excellence|NICE]] guidelines.