Blood culture is positive in which infection of staph. aureus-
**Core Concept**
Staphylococcus aureus is a gram-positive bacterium that can cause a wide range of infections, from skin and soft tissue infections to life-threatening diseases such as bacteremia and endocarditis. Blood culture positivity is a critical diagnostic tool for identifying bacteremia caused by S. aureus.
**Why the Correct Answer is Right**
Blood culture positivity in S. aureus infections is often associated with bacteremia, which occurs when the bacteria enter the bloodstream. This can happen through various routes, including direct inoculation from a skin or soft tissue infection, or through hematogenous spread from a distant site of infection. The bacteria can then be detected in blood cultures, which are typically collected from peripheral veins or central lines. The presence of S. aureus in blood cultures is often associated with severe disease and requires prompt antibiotic treatment.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while S. aureus can cause skin and soft tissue infections, blood culture positivity is not typically associated with these types of infections. Skin and soft tissue infections are often diagnosed through clinical examination and may not require blood cultures.
**Option B:** This option is incorrect because while S. aureus can cause pneumonia, blood culture positivity is not typically associated with this type of infection. Pneumonia is often diagnosed through chest imaging and clinical evaluation, and may not require blood cultures.
**Option C:** This option is incorrect because while S. aureus can cause osteomyelitis, blood culture positivity is not typically associated with this type of infection. Osteomyelitis is often diagnosed through a combination of clinical evaluation, imaging, and laboratory tests, and may not require blood cultures.
**Clinical Pearl / High-Yield Fact**
It's essential to note that S. aureus bacteremia can be associated with a high risk of complications, including endocarditis, sepsis, and metastatic abscesses. Therefore, prompt recognition and treatment of S. aureus bacteremia are critical to preventing these complications.
**Correct Answer: D**