Most common organism involved in nosocomial infection –
**Core Concept**
Nosocomial infections, also known as hospital-acquired infections, are infections that patients acquire during their stay in a healthcare facility. The most common causative organisms are often resistant to antibiotics and can spread quickly among patients and healthcare workers.
**Why the Correct Answer is Right**
The most common organism involved in nosocomial infections is Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). This is due to its ability to colonize the skin and mucous membranes, facilitating transmission among patients and healthcare workers. MRSA is resistant to beta-lactam antibiotics, making it challenging to treat.
* MRSA produces an enzyme called penicillin-binding protein 2a (PBP2a), which has a low affinity for beta-lactam antibiotics, allowing it to evade their effects.
* The spread of MRSA is often facilitated by inadequate hand hygiene, contaminated medical equipment, and poor infection control practices.
**Why Each Wrong Option is Incorrect**
**Option A:** Escherichia coli - While E. coli is a common cause of urinary tract infections, it is not the most common organism involved in nosocomial infections.
**Option B:** Pseudomonas aeruginosa - P. aeruginosa is a common cause of nosocomial infections, particularly in immunocompromised patients, but it is not the most common organism.
**Option C:** Klebsiella pneumoniae - K. pneumoniae is another common cause of nosocomial infections, but it is not the most common organism.
**Clinical Pearl / High-Yield Fact**
Methicillin-resistant S. aureus (MRSA) is a significant public health concern due to its ability to spread quickly among patients and healthcare workers. To prevent the spread of MRSA, healthcare facilities should implement strict infection control practices, including hand hygiene, use of personal protective equipment, and proper cleaning and disinfection of medical equipment.
**Correct Answer: C. Pseudomonas aeruginosa**