Final answer:
The most common bug (bacterium) causing acute endocarditis is Staphylococcus aureus. Acute endocarditis is a severe, rapidly progressing infection of the heart lining, requiring immediate and intense antibiotic therapy. In contrast, subacute endocarditis develops more slowly, potentially leading to heart valve replacement.
Step-by-step explanation:
Bacterial Endocarditis is an infection of the endocardium, the tissue lining the heart's muscles and valves. The most common causative agent of acute endocarditis is Staphylococcus aureus, which can quickly lead to severe consequences if not treated promptly. Other bacteria such as viridans streptococci, Enterococcus faecalis, and the HACEK group are also known to cause endocarditis. These pathogens often enter the bloodstream during medical procedures or due to breaches in barrier defenses, such as during dental work or from wounds.
People with preexisting conditions like damaged heart valves or a history of rheumatic fever are at a higher risk. Acute endocarditis requires immediate intensive intravenous antibiotic treatment based on antimicrobial susceptibility testing to prevent the rapid destruction of heart valves.
In contrast, subacute bacterial endocarditis progresses more slowly and might present with symptoms like fever over a period of months. It is characterized by blood clots and bacterial vegetations in the heart, which can eventually necessitate heart valve replacement.