MBIO 3401 FINAL EXAM-QUESTIONS AND
ANSWERS | WITH COMPLETE SOLUTION
What is the definition of infection?
the entry and growth of a microorganism within a host
What are the two possible outcomes of infection?
- disease: the microorganism produces symptoms and causes damage
- colonizations: the microorganism persists without causing disease
What is the difference between primary pathogen and opportunistic pathogen?
- primary pathogen: regularly causes disease is at least some individuals with normal defenses
- opportunistic pathogen: usually does not cause disease except in individuals with compromised
defenses
What is the definition of virulence?
the degree of pathogenicity
What is a virulence factor?
specific properties of a pathogen that promote infection and disease
From an ecological perspective, what types of symbiotic associations between organisms
can occur, and what type does a pathogen-host interaction represent?
- mutualism: both organisms benefit
- commensalism: one organism benefits and the other is not affected
- parasitism: one organism benefits at the expense of the other (pathogen-host interaction)
,Why does infectious disease occur at all?
- microbial entry into the host
- microbial attachment to surface tissues
- microbial growth and spread within the host
- microbial exit from the host
What are the portals of entry into the host?
- respiratory tract
- GI tract
- genitourinary tract
- skin wounds
- eye and ear
- placenta
How do microorganism attach to the surface tissues of the host?
pili and other (non-pilus) adhesions
What three microbial activities do many virulence factors promote during growth and
spread of the microbe within the host?
- scavenge nutrients
- penetrate host tissues
- counter host defenses
What are the specific virulence factors discusses in lecture?
,- capsule
- toxins (endotoxins and exotoxins)
- extracellular enzymes
What is the difference between endotoxins and exotoxins?
endotoxins are lipopolysaccharide and exotoxins are soluble proteins, gram + do not make
endotoxins
What are the five different types of exotoxins discussed in lecture?
- botulinum neurotoxin: blocks neurotransmitter release
- cholera enterotoxin: promotes massive fluid loss from intenstinal epithelium
- diphtheria cytotoxin: kills cells by inactivating translation
- hemolysins: lyse red blood cells by forming pores in membranes
- leukocidins: lyse white blood cells by forming pores in membranes
What types of extracellular enzymes can be produced?
- hyaluronidase: degrades hyaluronic acid
- collagenase: degrades collagen
- coagulase: promotes blood clot formation
- streptokinase: dissolve blood clots
- IgA protease: cleaves IgA antibodies
What are the portals of exit from the host?
- respiratory tract
- GI tract
, - genitourinary tract
- skin wounds
- eye and ear
- placenta
What are the major physical and chemical barriers to infection?
- tissue integrity
- flushing mechanisms
- antimicrobial substances
What are examples of antimicrobial substances produces by specific host cells and tissues?
- cationic antimicrobial peptides
- antibacterial fatty acids in perspiration
- lysozyme in tears and saliva
- lactoferrin in tears, saliva and milk
- gastric acids in stomach
- bile salts in intestine
- antiviral proteins in tissues
- antimicrobial proteins in blood and lymph
- transferrin in blood and lymph
What are the major biological barriers to infection?
- genetic resistance
- normal microbiota
ANSWERS | WITH COMPLETE SOLUTION
What is the definition of infection?
the entry and growth of a microorganism within a host
What are the two possible outcomes of infection?
- disease: the microorganism produces symptoms and causes damage
- colonizations: the microorganism persists without causing disease
What is the difference between primary pathogen and opportunistic pathogen?
- primary pathogen: regularly causes disease is at least some individuals with normal defenses
- opportunistic pathogen: usually does not cause disease except in individuals with compromised
defenses
What is the definition of virulence?
the degree of pathogenicity
What is a virulence factor?
specific properties of a pathogen that promote infection and disease
From an ecological perspective, what types of symbiotic associations between organisms
can occur, and what type does a pathogen-host interaction represent?
- mutualism: both organisms benefit
- commensalism: one organism benefits and the other is not affected
- parasitism: one organism benefits at the expense of the other (pathogen-host interaction)
,Why does infectious disease occur at all?
- microbial entry into the host
- microbial attachment to surface tissues
- microbial growth and spread within the host
- microbial exit from the host
What are the portals of entry into the host?
- respiratory tract
- GI tract
- genitourinary tract
- skin wounds
- eye and ear
- placenta
How do microorganism attach to the surface tissues of the host?
pili and other (non-pilus) adhesions
What three microbial activities do many virulence factors promote during growth and
spread of the microbe within the host?
- scavenge nutrients
- penetrate host tissues
- counter host defenses
What are the specific virulence factors discusses in lecture?
,- capsule
- toxins (endotoxins and exotoxins)
- extracellular enzymes
What is the difference between endotoxins and exotoxins?
endotoxins are lipopolysaccharide and exotoxins are soluble proteins, gram + do not make
endotoxins
What are the five different types of exotoxins discussed in lecture?
- botulinum neurotoxin: blocks neurotransmitter release
- cholera enterotoxin: promotes massive fluid loss from intenstinal epithelium
- diphtheria cytotoxin: kills cells by inactivating translation
- hemolysins: lyse red blood cells by forming pores in membranes
- leukocidins: lyse white blood cells by forming pores in membranes
What types of extracellular enzymes can be produced?
- hyaluronidase: degrades hyaluronic acid
- collagenase: degrades collagen
- coagulase: promotes blood clot formation
- streptokinase: dissolve blood clots
- IgA protease: cleaves IgA antibodies
What are the portals of exit from the host?
- respiratory tract
- GI tract
, - genitourinary tract
- skin wounds
- eye and ear
- placenta
What are the major physical and chemical barriers to infection?
- tissue integrity
- flushing mechanisms
- antimicrobial substances
What are examples of antimicrobial substances produces by specific host cells and tissues?
- cationic antimicrobial peptides
- antibacterial fatty acids in perspiration
- lysozyme in tears and saliva
- lactoferrin in tears, saliva and milk
- gastric acids in stomach
- bile salts in intestine
- antiviral proteins in tissues
- antimicrobial proteins in blood and lymph
- transferrin in blood and lymph
What are the major biological barriers to infection?
- genetic resistance
- normal microbiota
