A 67-year-old patient with chronic alcoholism presents with severe pneumonia. Blood cultures grow bacteria that evade phagocytosis and demonstrate increased virulence due to an external protective layer surrounding the cell wall. Which bacterial structure is primarily responsible for this immune evasion?
Flagella
Capsule
Fimbriae
Lipopolysaccharide
Peptidoglycan
The Correct Answer is B
A. Flagella: Flagella are whip-like appendages that provide motility to bacteria, allowing them to move toward nutrients or away from harmful environments. While motility can contribute to colonization, flagella do not provide a protective barrier against phagocytosis or immune system attack.
B. Capsule: The capsule is an external polysaccharide or protein layer that surrounds the bacterial cell wall. It prevents recognition and ingestion by phagocytes, inhibits complement activation, and contributes to increased virulence. Encapsulated bacteria, such as Streptococcus pneumoniae, are particularly problematic in patients with weakened immune systems, like those with chronic alcoholism, because the capsule impedes effective immune clearance.
C. Fimbriae: Fimbriae are short, hair-like projections on the bacterial surface that facilitate attachment to host cells and surfaces. They play a role in colonization and biofilm formation but do not directly prevent phagocytosis or enhance survival against immune defenses.
D. Lipopolysaccharide: Lipopolysaccharide (LPS) is a component of the outer membrane of Gram-negative bacteria that contributes to endotoxin activity, triggering inflammation and septic shock. While LPS can affect host immune responses, it does not provide a direct physical barrier to phagocytosis.
E. Peptidoglycan: Peptidoglycan forms the rigid structural layer of the bacterial cell wall, providing shape and protection against osmotic pressure. Although essential for bacterial integrity, peptidoglycan does not prevent immune recognition or phagocytosis in the way that a capsule does.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Dimorphic fungi have the unique ability to exist in two distinct morphological forms depending on the temperature of their environment. At environmental or cooler temperatures (usually around 25°C), they grow as filamentous molds, producing hyphae and spores that allow them to survive and reproduce outside a host. At body temperature (37°C), they transition into a yeast form, which is better adapted for survival and pathogenicity within human tissues. This temperature-dependent dimorphism is a key factor in their ability to cause systemic infections. Examples include Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides immitis, all of which demonstrate this adaptive morphological shift.
Correct Answer is D
Explanation
A. All viruses are released exclusively through host cell apoptosis: Viral release mechanisms vary depending on the type of virus. While some infections may induce apoptosis, this is not the universal mechanism of viral release. Many viruses use lysis or budding rather than programmed cell death.
B. Non-enveloped viruses exit the host cell by exocytosis: Non-enveloped viruses typically lack a lipid membrane and are most commonly released through host cell lysis. Lysis disrupts the plasma membrane, allowing viral particles to escape. Exocytosis is more characteristic of enveloped viruses.
C. Enveloped viruses are released only after host cell lysis: Enveloped viruses generally acquire their lipid envelope by budding through the host cell membrane. This process allows viral release without immediate destruction of the host cell, unlike lysis.
D. Release occurs through budding in enveloped viruses or cell lysis in non-enveloped viruses: Enveloped viruses exit by budding through the host cell membrane, incorporating host-derived lipids into their envelope. Non-enveloped viruses are released through lysis, which ruptures the host cell and releases mature virions.
E. Viral release requires active transport through nuclear pores: Nuclear pores are involved in transport between the nucleus and cytoplasm, particularly for viruses that replicate in the nucleus. However, viral release from the cell occurs at the plasma membrane or through cell lysis, not via nuclear pores.
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