Pathogens and disease Knowledge-Based Download PDF

Questions

1. 1.

   Which of the following characteristics correctly distinguishes bacterial exotoxins from bacterial endotoxins?

   • A) Exotoxins are integral lipopolysaccharide components of the outer membrane, whereas endotoxins are soluble proteins actively secreted by living cells.
   • B) Exotoxins are soluble proteins secreted by living bacterial cells, whereas endotoxins are lipopolysaccharide components released primarily upon cell lysis.
   • C) Exotoxins are heat-stable lipids found exclusively in Gram-negative bacteria, whereas endotoxins are heat-labile enzymes produced by Gram-positive bacteria.
   • D) Exotoxins trigger systemic inflammatory responses only at extremely high concentrations, whereas endotoxins exhibit highly specific enzymatic activity at minute doses.
2. 2.

   Which of the following best describes an opportunistic pathogen?

   • A) An infectious agent that naturally transfers from an animal reservoir to cause disease in human populations
   • B) A microbe that cannot synthesize its own proteins and must replicate inside host cells by hijacking cellular machinery
   • C) A virulent organism capable of consistently initiating infection and causing disease in individuals with healthy immune defenses
   • D) A microorganism that typically causes disease only when the host's immune system is weakened or normal physical barriers are breached
3. 3.

   Which of the following best describes the role of a biological vector in the transmission of infectious diseases?

   • A) An inanimate surface or object that harbors viable pathogens between host contacts
   • B) A living organism, typically an arthropod, that carries and transmits an infectious agent from one host or reservoir to another
   • C) A non-pathogenic microorganism residing in the human microbiota that prevents colonization by foreign invaders
   • D) An environmental source such as contaminated soil or water where pathogens normally live and multiply
4. 4.

   Which of the following correctly pairs an infectious human disease with the category of pathogen that causes it?

   • A) Cholera – Virus
   • B) Athlete's foot – Bacterium
   • C) Malaria – Protozoan
   • D) Influenza – Fungus
5. 5.

   Which of the following correctly describes a fundamental difference between pathogenic bacteria and viruses?

   • A) Bacteria lack a cellular structure and replicate only inside a host cell, whereas viruses have a peptidoglycan cell wall and can be eliminated using antibiotics.
   • B) Both bacteria and viruses possess ribosomes for protein synthesis, but only bacterial infections can be treated effectively with antiviral medications.
   • C) Bacteria are cellular organisms that can often be treated with antibiotics, whereas viruses are acellular particles that are unaffected by antibiotics.
   • D) Viruses are independent single-celled organisms that reproduce by binary fission, whereas bacteria require a living host cell to replicate.