A physician is reviewing several cases of suspected infective endocarditis. The causative microorganisms often have distinct clinical associations based on patient demographics and antecedent procedures. For each patient presentation described below, identify the most probable responsible pathogen.
- A 32-year-old with a history of injection drug use, presenting with high fever, a tricuspid regurgitation murmur, and cavitary lung lesions.Staphylococcus aureus
- A 65-year-old with urinary retention who develops a new systolic murmur and fever three weeks following a cystoscopy.Enterococcus faecalis
- A 48-year-old with severe gingivitis who develops subacute fevers and Osler nodes one month after a deep dental scaling procedure.Viridans group streptococci
- A 58-year-old who develops a paravalvular leak and persistent bacteremia one month following mechanical mitral valve replacement.Staphylococcus epidermidis
- A 70-year-old presenting with insidious endocarditis who is subsequently diagnosed with asymptomatic ascending colon adenocarcinoma.Streptococcus gallolyticus
Answer
The correct matches rely on identifying the specific risk factor for each pathogen: injection drug use (Staphylococcus aureus), genitourinary instrumentation (Enterococcus faecalis), dental work (Viridans group streptococci), recent prosthetic valves (Staphylococcus epidermidis), and colonic malignancy (Streptococcus gallolyticus).
Each pathogen presents with distinct epidemiological associations. Staphylococcus aureus causes acute, right-sided endocarditis in IV drug users. Enterococcus faecalis often follows GU tract manipulation. Viridans group streptococci are tied to poor dentition and dental procedures. Staphylococcus epidermidis is the leading cause of early prosthetic valve infections. Streptococcus gallolyticus is highly associated with colonic lesions.
Step-by-Step Solution
Key Concept
Infective Endocarditis Microbiology and Risk Factors