The morphology of bronchiectasis

Correct Answer: A

Rationale: Bronchiectasis shows airway dilation up to four times normal size (A), a hallmark of permanent damage. Choice B is false; it affects lower lobes (gravity-dependent). Choice C is incorrect; it's usually bilateral. Choice D is wrong; squamous metaplasia occurs. Choice E (variable histology) is true. Page 728 details A's dilation chronic inflammation/necrosis widens bronchi, with fibrosis or abscesses in severe cases, contrasting with B's lobe error or D's metaplasia denial.

Correct Answer: A

Rationale: Staph aureus pneumonia is common with endocarditis in IV drug users (A), via hematogenous spread. Choice B is false; it causes complications (e.g., empyema). Choice C is incorrect; Klebsiella, not S aureus, targets malnourished/alcoholics. Choice D is wrong; it follows viral infections (e.g., influenza), not mumps. Choice E (nosocomial) is true. Page 748 links A's association S aureus's virulence in IVDU leads to septic emboli, distinguishing it over B's complication denial or C's group error.

Correct Answer: A

Rationale: Pulmonary non-Hodgkin lymphoma must be excluded in HIV pneumonia (A), due to malignancy risk. Choice B is false; common pathogens (e.g., S pneumoniae) also dominate. Choice C is incorrect; M avium occurs late (CD4 <50). Choice D is wrong; TB strikes early. Choice E (none true) is invalid. Page 757 notes A's necessity lymphoma mimics infection radiologically, distinguishing it over B's exclusion or C's timing error.

Correct Answer: A

Rationale: Adhesins are proteins or structures on microbial surfaces that enable attachment to host respiratory tissues, a critical step in infection. They bind to specific receptors on epithelial cells, like those in the lungs or nasal passages, allowing pathogens to colonize and evade clearance. Lipopolysaccharide, a bacterial endotoxin, triggers inflammation but doesn't aid attachment. Hyaluronidase degrades host tissues for invasion, not initial adhesion. Capsules resist phagocytosis but primarily protect, not attach. Adhesins' specificity e.g., in Streptococcus pneumoniae or influenza virus makes them vital for establishing respiratory infections, initiating pathogenesis. This attachment precedes toxin release or tissue damage, underlining its importance in microbial strategies, a key focus in understanding respiratory disease mechanisms.

Correct Answer: B

Rationale: Coccidioidomycosis, dubbed Valley fever, is caused by Coccidioides fungi, endemic to the U.S. Southwest (e.g., San Joaquin Valley), inhaled as spores from soil, causing pneumonia-like symptoms. Histoplasmosis, from Histoplasma capsulatum, thrives in bird droppings, common in the Mississippi Valley. Blastomycosis (Blastomyces dermatitidis) affects lungs and skin, linked to moist environments. Aspergillosis (Aspergillus spp.) targets immunocompromised lungs, not region-specific like Valley fever. Coccidioidomycosis's arid habitat and flu-like presentation distinguish it, requiring antifungals like fluconazole, unlike broader-spectrum treatments for others, emphasizing geographic and clinical uniqueness in fungal respiratory infections.