Endocarditis causes

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ahmed Zaghw, M.D. [2]

Overview

The three most common causes of bacterial endocarditis include streptococcus viridans, staphylococci and enterococcus.

Epidemiological Clues in Etiological Diagnosis of Culture-Negative Endocarditis

Epidemiological features	Common Microorganism(s)
Injection drug use	S aureus oxacillin-resistant strains Coagulase-negative staphylococci β-Hemolytic streptococci Fungi Aerobic Gram-negative bacilli, including Pseudomonas aeruginosa
Indwelling cardiovascular medical devices	S aureus Coagulase-negative staphylococci Fungi Aerobic Gram-negative bacilli Corynebacterium sp
Genitourinary disorders Genitourinary infection Genitourinary manipulation pregnancy Delivery Abortion	Enterococcus sp Group B streptococci (S agalactiae) Listeria monocytogenes Aerobic Gram-negative bacilli Neisseria gonorrhoeae
Chronic skin disorders	S aureus β-Hemolytic streptococci
Poor dental health, dental procedures	Viridans group streptococci “Nutritionally variant streptococci” Abiotrophia defectiva Granulicatella sp Gemella sp HACEK organisms
Alcoholism, cirrhosis	Bartonella sp Aeromonas sp Listeria sp S pneumoniae β-Hemolytic streptococci
Burn patients	S aureus Aerobic Gram-negative bacilli, including Pseudomonas aeruginosa Fungi
Diabetes mellitus	S aureus β-Hemolytic streptococci S pneumoniae
Early ( < 1 y) prosthetic valve placement	Coagulase-negative staphylococci S aureus Aerobic Gram-negative bacilli Fungi Corynebacterium sp Legionella sp
Late ( > 1 y) prosthetic valve placement	Coagulase-negative staphylococci S aureus Viridans group streptococci Enterococcus species Fungi Corynebacterium sp
Dog–cat exposure	Bartonella sp Pasteurella sp Capnocytophaga sp
Contact with contaminated milk Contact with infected farm animals	Brucella sp Coxiella burnetii Erysipelothrix sp
Homeless, body lice	Bartonella sp
AIDS	Salmonella sp S pneumoniae S aureus
Pneumonia, meningitis	S pneumoniae
Solid organ transplant	S aureus Aspergillus fumigatus Enterococcus sp Candida sp
Gastrointestinal lesions	S bovis Enterococcus sp Clostridium septicum

Common Causes

Many types of organism can cause infective endocarditis. These are generally isolated by blood culture, where the patient's blood is sampled under sterile conditions, and any growth is noted and identified. It is therefore important to draw blood cultures before initiating antibiotic therapy. 70% of cases of endocarditis are due to the following three pathogens:

1. Alpha-haemolytic streptococci, that are present in the mouth will often be the organism isolated if a dental procedure caused the bacteraemia.
2. If the bacteraemia was introduced through the skin, such as contamination in surgery, during catheterization, or in an IV drug user, Staphylococcus aureus is common.
3. A third important cause of endocarditis is Enterococci. These bacteria enter the bloodstream as a consequence of abnormalities in the gastrointestinal or urinary tracts. Enterococci are increasingly recognized as causes of nosocomial or hospital-acquired endocarditis. This contrasts with alpha-haemolytic streptococci and Staphylococcus aureus which are causes of community-acquired endocarditis.

Less Common Causes

Some organisms, when isolated, give valuable clues to the cause, as they tend to be specific.

• Candida albicans, a yeast, is associated with IV drug users and the immunocompromised. Fungal endocarditis accounts for 5% of cases of native endocarditis and 10% of cases of prosthetic valve endocarditis. A diagnosis of fungal endocarditis is difficult, because many patients are afebrile with a normal white blood cell count (WBC). The fungus is often difficult to culture, and blood cultures are typically negative. Fungal infections often result in large vegetations, systemic embolization, myocardial invasion, and are extremely resistant to medical therapy. Early surgical intervention is warranted because medical mortality approaches 100% Anti-fungal therapy for life is required.
• 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.
• Streptococcus bovis and Clostridium septicum, which are part of the natural flora of the bowel, are associated with colonic malignancies. When they present as the causative agent in endocarditis, it usually indicates that a colonoscopy should be performed due to worries regarding hematogenous spread of bacteria from the colon due to the neoplasm breaking down the barrier between the gut lumen and the blood vessels which drain the bowel.
• HACEK organisms are a group of bacteria that live on the dental gums, and can be seen with IV drug abusers who contaminate their needles with saliva. Patients may also have a history of poor dental hygiene, or pre-existing valvular disease.

Causes by Organ System

Cardiovascular	Asymmetric septal hypertrophy, Calcific aortic stenosis, Cardiac catheterization, Cardiac surgery, Congenital Heart Disease, Mitral valve prolapse, Prosthetic heart valve, Septal defects, Valve disease, Previous bacterial endocarditis, Rheumatic Heart Disease, Sclerotherapy, Cardiac myxoma, Tetralogy of Fallot, Structural heart disease, Patent ductus arteriosus, Coarctation of the aorta, Calcific valvular disease, Bicuspid aortic valves
Chemical / poisoning	No underlying causes
Dental	Dental extractions, Dental implants, Root canals
Dermatologic	Skin infection
Drug Side Effect	IV drug use
Ear Nose Throat	Adenoidectomy
Endocrine	No underlying causes
Environmental	No underlying causes
Gastroenterologic & Genito-Uriner	Biliary tract surgery, Cystoscopy, Endoscopic retrograde cholangiopancreatography, Urethral dilation, Prostatic surgery, Whipple disease, Ulcerative lesions of the colon due to carcinoma, Ulcerative lesions of the colon due to inflammatory bowel disease, Peritoneovenous shunts for ascites
Genetic	Marfan's Syndrome
Hematologic	No underlying causes
Iatrogenic	Urethral dilation, Prostate surgery, Cystoscopy
Infectious Disease	Diphtheria, Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus bovis, Viridans streptococci, Group A streptococcus, Gram negative rods, Enterococuss, Candida, Tuberculosis, Salmonellosis, HIV, Bacteroides, HACEK Group of organism
Musculoskeletal / Ortho	No underlying causes
Neurologic	Ventriculoatrial shunts for hydrocephalus
Nutritional / Metabolic	No underlying causes
Obstetrics & Gynecology	Childbirth
Oncologic	Paraneoplastic syndrome
Opthalmologic	No underlying causes
Overdose / Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	Respiratory infection, Respiratory tract procedures
Renal / Electrolyte	Chronic hemodialysis
Rheum / Immune / Allergy	Acute rheumatic fever, Systemic lupus erythematosus, Marantic endocarditis, Immune impairment
Trauma	No underlying causes
Miscellaneous	Surgical systemic-pulmonary shunts and conduits

Causes in Alphabetical Order

Asymmetric septal hypertrophy Acute rheumatic fever Adenoidectomy Aortic valve regurgitation Aortic valve stenosis Bacteroides Bicuspid aortic valves Biliary tract surgery Calcific aortic stenosis Calcific valvular disease Candida albicans Cardiac catheterization Cardiac myxoma Cardiac surgery Chronic hemodialysis Coagulase-negative staphylococci Coarctation of the aorta Congenital Heart Disease Cystoscopy Dental extractions Dental implants Dental sepsis Diphtheria Endoscopic retrograde cholangiopancreatography Enterococci Fungi Gram negative rods Group A streptococcus HACEK Group of organism History of endocarditis HIV Immune impairment Intravascular procedure in settings of bacteremia Intravenous catheter-relatedinfection Intravenous drug use Marantic endocarditis

Mitral valve prolapse with regurgitation Mycobacterium avium-intracellulare Non-HACEK gram-negative bacteria Other streptococci Paraneoplastic syndrome Patent ductus arteriosus Peritoneovenous shunts for ascites Pregnancy Previous bacterial endocarditis Prostatic surgery Prosthetic heart valve Prosthetic heart valves Q fever Respiratory tract procedures Rheumatic Heart Disease Root canals procedure S. aureus Salmonellosis Sclerotherapy Septal defects Skin infection Staphylococcus epidermidis Streptococcus bovis Streptococcus milleri Streptococcus viridans structural heart disease Surgical systemic-pulmonary shunts and conduits Systemic lupus erythematosus Tetralogy of Fallot Tuberculosis Ulcerative lesions of the colon due to inflammatory bowel disease Ulcerative lesions of the colon due to carcinoma Urethral dilation Ventricular septal defect Ventriculoatrial shunts for hydrocephalus Whipple disease

References