What is the common etiologic organism for native-valve endocarditis in non-IV drug users?

What is the common etiologic organism for native-valve endocarditis in non-IV drug users?

• A. Streptococcus viridans
• B. Staphylococcus aureus
• C. Pseudomonas aeruginosa
• D. Enterococcus faecalis

Answer: (A)

In native-valve endocarditis among patients who are not IV drug users, the usual culprit is viridans group streptococci from the oral cavity. These organisms are part of normal oral flora and can enter the bloodstream after dental work or with poor dentition. Once in circulation, they readily adhere to damaged or abnormal valve tissue, aided by surface adhesins and dextran production, seeding a valve and causing a subacute infection. That explains why the presentation tends to be gradual with vague systemic symptoms rather than a rapid, fulminant illness. Other organisms fit different clinical scenarios. Staphylococcus aureus often causes acute endocarditis and is especially common in IV drug users or after invasive procedures, leading to rapid valve destruction. Pseudomonas aeruginosa is also more associated with IV drug use or nosocomial infections and prosthetic devices. Enterococcus faecalis is linked to genitourinary or gastrointestinal procedures and older patients, and can cause endocarditis but is less characteristic as the top cause in non-IV drug users with native valves.

In native-valve endocarditis among patients who are not IV drug users, the usual culprit is viridans group streptococci from the oral cavity. These organisms are part of normal oral flora and can enter the bloodstream after dental work or with poor dentition. Once in circulation, they readily adhere to damaged or abnormal valve tissue, aided by surface adhesins and dextran production, seeding a valve and causing a subacute infection. That explains why the presentation tends to be gradual with vague systemic symptoms rather than a rapid, fulminant illness.

Other organisms fit different clinical scenarios. Staphylococcus aureus often causes acute endocarditis and is especially common in IV drug users or after invasive procedures, leading to rapid valve destruction. Pseudomonas aeruginosa is also more associated with IV drug use or nosocomial infections and prosthetic devices. Enterococcus faecalis is linked to genitourinary or gastrointestinal procedures and older patients, and can cause endocarditis but is less characteristic as the top cause in non-IV drug users with native valves.