Which pathogens adhere to respiratory epithelium-
**Core Concept**
Adherence of pathogens to the respiratory epithelium is a crucial step in the pathogenesis of respiratory infections. This process involves the interaction between bacterial surface adhesins and host epithelial cell surface receptors.
**Why the Correct Answer is Right**
The correct answer involves the adherence of specific pathogens to the respiratory epithelium. For example, *Streptococcus pneumoniae* and *Haemophilus influenzae* utilize the pneumococcal surface protein A (PspA) and the H. influenzae outer membrane protein P2 (P2) respectively to adhere to the host epithelial cells. These adhesins interact with host cell surface receptors such as platelet-activating factor receptor (PAFR) and glycoproteins like CD14. This adherence facilitates the colonization and invasion of the respiratory tract, leading to infection.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because *Escherichia coli* is more commonly associated with urinary tract infections, where it adheres to the uroepithelium through adhesins like FimH.
**Option B:** Incorrect because *Staphylococcus aureus* is a skin commensal that can cause infections by invading skin tissue, but it does not specifically adhere to the respiratory epithelium.
**Option C:** Incorrect because *Pseudomonas aeruginosa* is a opportunistic pathogen that can infect immunocompromised individuals, but it is not specifically known for adhering to the respiratory epithelium.
**Clinical Pearl / High-Yield Fact**
The adherence of pathogens to the respiratory epithelium is an essential step in the development of respiratory infections. Understanding the specific adhesins and receptors involved can aid in the development of targeted therapeutic strategies.
**Correct Answer:** C.