Which symptoms are associated with the different etiologic agents of infective endocarditis (IE)?

Updated: Jan 03, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
  • Print

Different causative organisms tend to give rise to varying clinical manifestations of IE, as shown in the Table below.

Table 1. Clinical Features of Infective Endocarditis According to Causative Organism (Open Table in a new window)

Causative Organism(s)

Clinical Features of IE

Staphylococcus aureus

  • Overall, S aureus infection is the most common cause of IE, including PVE, acute IE, and IVDA IE.

  • Approximately 35-60.5% of staphylococcal bacteremias are complicated by IE.

  • More than half the cases are not associated with underlying valvular disease.

  • The mortality rate of S aureus IE is 40-50%.

  • S aureus infection is the second most common cause of nosocomial BSIs, second only to CoNS infection.

  • The incidence of MRSA infections, both the hospital- and community-acquired varieties, has dramatically increased (50% of isolates). Sixty percent of individuals are intermittent carriers of MRSA or MSSA.

  • The primary risk factor for S aureus BSI is the presence of intravascular lines. Other risk factors include cancer, diabetes, corticosteroid use, IVDA, alcoholism, and renal failure.

  • The realization that approximately 50% of hospital- and community-acquired staphylococcal bacteremias arise from infected vascular catheters has led to the reclassification of staphylococcal BSIs. BSIs are acquired not only in the hospital but also in any type of health care facility (eg, nursing home, dialysis center).

  • Of S aureus bacteremia cases in the United States, 7.8% (200,000) per year are associated with intravascular catheters.

Streptococcus viridans

  • This organism accounts for approximately 50-60% of cases of subacute disease.

  • Most clinical signs and symptoms are mediated immunologically.

Streptococcus intermedius group

  • These infections may be acute or subacute.

  • S intermedius infection accounts for 15% of streptococcal IE cases.

  • Members of the S intermedius group, especially S anginosus, are unique among the streptococci in that they can actively invade tissue and form abscesses, often in the CNS.


  • Approximately 5% of subacute cases of IE are due to infection with Abiotrophia species.

  • They require metabolically active forms of vitamin B-6 for growth.

  • This type of IE is associated with large vegetations that lead to embolization and a high rate of posttreatment relapse.

Group D streptococci

  • Most cases are subacute.

  • The source is the gastrointestinal or genitourinary tract.

  • It is the third most common cause of IE.

  • They pose major resistance problems for antibiotics.

Nonenterococcal group D

  • The clinical course is subacute.

  • Infection often reflects underlying abnormalities of the large bowel (eg, ulcerative colitis, polyps, cancer).

  • The organisms are sensitive to penicillin.

Group B streptococci

  • Acute disease develops in pregnant patients and older patients with underlying diseases (eg, cancer, diabetes, alcoholism).

  • The mortality rate is 40%.

  • Complications include metastatic infection, arterial thrombi, and congestive heart failure.

  • It often requires valve replacement for cure.

Group A, C, and G streptococci

  • Acute disease resembles that of S aureus IE (30-70% mortality rate), with suppurative complications.

  • Group A organisms respond to penicillin alone.

  • Group C and G organisms require a combination of synergistic antibiotics (as with enterococci).

Coagulase-negative S aureus

  • This causes subacute disease.

  • It behaves similarly to S viridans infection.

  • It accounts for approximately 30% of PVE cases and less than 5% of NVE cases. [23]

Staphylococcus lugdunensis
  • Staphylococcus lugdunensis is another coagulase-negative Staphylococcus species but is extremely aggressive compared to coagulase-positive S aureus. S lugdunensis frequently causes IE. [24]

Pseudomonas aeruginosa

  • This is usually acute, except when it involves the right side of the heart in IVDA IE.

  • Surgery is commonly required for cure.

HACEK (ie, Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae)

  • These organisms usually cause subacute disease.

  • They account for approximately 5% of IE cases.

  • They are the most common gram-negative organisms isolated from patients with IE.

  • Complications may include massive arterial emboli and congestive heart failure.

  • Cure requires ampicillin, gentamicin, and surgery.


  • These usually cause subacute disease.

  • The most common organism of both fungal NVE and fungal PVE is Candida albicans.

  • Fungal IVDA IE is usually caused by Candida parapsilosis or Candida tropicalis.

  • Aspergillus species are observed in fungal PVE and NIE.


  • The most commonly involved species is Bartonella quintana.

  • IE typically develops in homeless males who have extremely substandard hygiene. Bartonella must be considered in cases of culture-negative endocarditis among homeless individuals.

Multiple pathogens (polymicrobial)

  • Pseudomonas and enterococci are the most common combination of organisms.

  • It is observed in cases of IVDA IE

  • The cardiac surgery mortality rate is twice that associated with single-agent IE. [25]

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!