Many microorganisms can cause<unk> . These are generally isolated by blood culture, where the patient's blood is drawn and any growth is noted and identified. The term bacterial endocarditis (BE) commonly is used, reflecting the fact that most cases of<unk>  are due to bacteria; however,<unk>  <unk>  has become the preferred term. Bacterial Staphylococcus aureus is the leading cause of<unk>  in most parts of the world and is responsible for about 31% of cases. Staphylococcus aureus is the most common cause of endocarditis in people who use intravenous drugs. Viridans streptococci and Enterococci are the second and third most common organisms responsible for<unk> . Viridans streptococci are a common cause of<unk>  in South America. Other Streptococci are also a frequent cause.<unk>  due to Streptococcus bovis occurs more commonly in Europe than in North America. HACEK group of bacteria are also rare causes of<unk>  in North America. 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. 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. Viridans alpha-hemolytic streptococci, that are present in the mouth, are the most frequently isolated microorganisms when the infection is acquired in a community setting. In contrast, 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. Enterococcus can enter the bloodstream as a consequence of abnormalities in the gastrointestinal or genitourinary tracts. 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. P. aeruginosa can infect a child through foot punctures, and can cause both endocarditis and septic arthritis. * S. bovis and Clostridium septicum, which are part of the natural flora of the bowel, are associated with colon cancers. 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. * Less commonly reported bacteria responsible for so called "culture negative endocarditis" include Bartonella, Chlamydia psittaci, and Coxiella. 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<unk>  caused by unusual organisms have been published. Cutibacterium spp., which are normal skin flora, have been responsible for<unk> , preferably in patients with prosthetic heart valves, in rare cases leading to death.Tropheryma whipplei has caused endocarditis without gastrointestinal involvement. Citrobacter koseri was found in an immunocompetent adult. Neisseria bacilliformis was found in a person with a bicuspid aortic valve. Fungal Fungal endocarditis (FE) is often fatal and one of the most serious forms of<unk> . The types of fungi most seen associated with this disease are: Candida albicans is found as a spherical or oval budding yeast. It is associated with endocarditis in people who inject drugs, patients with prosthetic valves, and immunocompromised patients. It forms biofilms around thick-walled resting structures like prosthetic heart valves and additionally colonizes and penetrates endothelial walls. C. albicans is responsible for 24-46% of all the cases of FE, and its mortality rate is 46.6–50%. Other fungi demonstrated to cause endocarditis are Histoplasma capsulatum and Aspergillus. Aspergillus contributes to roughly 25% of FE cases. Endocarditis with Tricosporon asahii has also been reported in a case report. Risk factors Risk factors for<unk>  are based on the premise that in a healthy individual, bacteremia (bacteria entering the bloodstream) is cleared quickly with no adverse consequences. However, if a heart valve is damaged, the bacteria can attach themselves to the valve, resulting in<unk> . Additionally, in individuals with weakened immune systems, the concentration of bacteria in the blood can reach levels high enough to increase the probability that some will attach to the valve. Some significant risk factors are listed here: * Artificial heart valves * Intracardiac devices, such as implantable cardioverter-defibrillators * Unrepaired cyanotic congenital heart defects * History of<unk>  * Neoplastic disease * Chronic rheumatic heart disease, which is an autoimmune response to repeated Streptococcus pyogenes infection (mostly in the developing world) * Age-related degenerative valvular lesions * Congenital heart valve abnormalities * Hemodialysis, a medical procedure that filters the blood of individuals with kidney failure * Poor oral hygiene * Coexisting conditions, especially ones that suppress immunity. Diabetes mellitus, alcohol use disorder, chronic liver disease, HIV/AIDS, and intravenous drug use all fall in this category More detailed descriptions of these and other risk factors are provided below. Other conditions that result in large numbers of bacteria entering into the bloodstream include colorectal cancer (mostly Streptococcus bovis), serious urinary tract infections (mostly enterococci), and drug injection (Staphylococcus aureus). With a large number of bacteria, even a normal heart valve may become infected. A more virulent organism (such as Staphylococcus aureus) can cause<unk>  by infecting even a normal heart valve. People who inject drugs tend to get their right-sided heart valves infected because the veins that are injected drain into the right side of the heart. In rheumatic heart disease, infection occurs on the aortic and the mitral valves on the left side of the heart. Other factors that increase the risk of developing<unk>  are low levels of white blood cells, immunodeficiency or immunosuppression, malignancy, diabetes mellitus, and excessive alcohol use. Dental operations In the past, one in eight cases of<unk>  was because of bacteremia caused by dental procedures (in most cases due to Streptococcus viridans, which reside in the oral cavity), such as cleaning or extraction of a tooth. This was thought to be more clinically significant than it actually was. However, it is important that a dentist or a dental hygienist be told of any heart problems before commencing treatment. Antibiotics are administered to patients with certain heart conditions as a precaution, although this practice has changed in the US, with new American Heart Association guidelines released in 2007, and in the UK as of March 2008 due to new NICE guidelines. Everyday tooth brushing and flossing will similarly cause bacteremia, so a high standard of oral health should be adhered to at all times. Although there is little evidence to support antibiotic prophylaxis for dental treatment, the current American Heart Association guidelines are highly accepted by clinicians and patients.
Infective endocarditis
Libman–Sacks endocarditis
Loeffler endocarditis
Nonbacterial thrombotic endocarditis
Subacute bacterial endocarditis
Tuberculous pericarditis
Nocardiosis
Ischemic cardiomyopathy