lecture 32 Flashcards
infectious diseases (28 cards)
List the different classes of pathogens.
viruses
bacteria
fungi
parasites
Explain the characteristics of each class of pathogen.
viruses:
- DNA/RNA and protein coat
- cannot reproduce outside of cells
- antivirals slow viral replication
bacteria:
- microscopic cell without nucleus
- common on keyboards, water fountains, toilets, etc
- antibiotics slow bacterial reproduction
fungi:
- microscopic, unicellular (yeasts) or multicellular (molds)
- usually infect body surfaces and openings
- antifungals destroy the cell walls
protozoa:
- microscopic, unicellular
- common in water supplies of developing countries
- antiprotozoal drugs interfere with protozoan metabolism
worms:
- multicellular
- prefer to live within body spaces and cells
- antihelmintics interfere with the worm’s metabolism
prions:
- the protein (PrP) is found throughout the body; however the PrP in infectious materials is misfolded
- protein found in infected animals
- current research for effective treatment
Provide examples of each class of pathogen.
viruses:
varicella zoster virus (chicken pox- remains latent)
HPV (causes cervical cancer)
influenza
the common cold (rhinovirus)
HIV/AIDS
bacteria:
lyme disease and syphilis (spirochetes, anaerobic)
pneumonia (mycoplasmas, no cell wall)
rocky mountain spotted fever (obligate intracellular pathogens, transmitted by mites, fleas, etc.)
chlamydia (chlamudiaceae, obligate intracellular pathogens, transmitted via person-to-person contact)
strep throat
some sinus and lung infections
some food poisonings
fungi:
ringworm, athlete’s foot, and jock itch (superficial mycoses, cooler cutaneous surfaces)
candidiasis and aspergillosis (systemic mycoses, deep tissue)
parasites:
malaria, amebic dysentery, and giardiasis (protozoa, unicellular animals)
roundworms, tapeworms, and flukes (helminths, wormlike parasites)
scabies, chiggers, lice, and fleas (parasitic arthropods)
Distinguish different modes of transmissions and sources of pathogens.
modes of transmission
penetration:
abrasions, burns, needles, insect/animal bites
direct contact:
sexually transmitted infection
congenital infection (vertical, mom to baby)
ingestion:
cholera, typhoid fever, food poisoning, etc.
low pH of gastric acid acts as a barrier for many pathogens, but some are resistant to low pH
normal bacteria flora of the bowel compete with pathogens
inhalation:
the respiratory tract is equipped with multiple-tiered defense system (mucous membrane, couching, antibodies and enzymes, phagocytosis, etc.)
smoking and diseases such as cystic fibrosis impair the defense system
sources
endogenous:
opportunistic infection acquired from the host’s own microbial flora
exogenous:
environment (food, water, soil, air)
person:
direct contact
fomites:
inanimate objects contaminated with infected body fluids
animal:
zoonoses (passed from animal to human)
vector:
biting arthropod
place:
nosocomial infection (healthcare aquired)
community acquired
Explain the characteristics of the stages of the disease course.
endemic describes relatively stable incidence and prevalence in a particular geographic region
epidemic describes an abrupt and unexpected increase in the incidence of disease over endemic rates
pandemic refers to the spread of disease beyond continental boundaries
Distinguish the pathological functions of each class of virulence factors.
exotoxins:
proteins released by pathogenic bacteria
inactive key cellular constituents
many are superantigens
endotoxins:
lipids and polysaccharides, not released
can induce clotting, bleeding, inflammation, hypotension, and fever (endotoxin shock)
adhesion factors:
bind to macromolecules in the surface of host cells
adhesion is critical for the colonization of the pathogens
some pathogens form a mucous layer (slime)
evasive factors:
inactivate host’s immune system
ex: leukocidins form pores in the cell membrane of neutrophils and macrophages
some pathogens survive and reproduce within phagocytes after phagocytosis by neutralizing lysosomal contents with evasive factors
invasive factors:
facilitate the penetration of anatomic barriers
ex: pseudomonas aeruginosa collagenase breaks skin
Commensalism
the colonizing bacteria acquire nutrition, and the host gets neither benefit nor harm
commensal bacteria in a human body (normal flora) are 10x more than human cells
Mutualism
both microorganism and the host derive benefits from the interaction
Incidence
the number of new cases of an infectious disease that occur within a defined population over an established period of time
Disease prevalence
the number of active cases at any given time in a population
Endemic
describes relatively stable incidence and prevalence in a particular geographic region
Epidemic
describes an abrupt and unexpected increase in the incidence of disease over endemic rates
Pandemic
refers to the spread of disease beyond continental boundaries
Fomites
inanimate objects contaminated with infected body fluids
(rhinovirus shared through toys, HIV and Hep B virus shared by syringes)
Zoonoses
infectious diseases passed from other animal species to humans
70% of emerging viral infections
ex: HIV, rabies, plague, influenza, SARS, MERS, etc.
Nosocomial infection
healthcare-associated infection
community acquired
Congenital infection
infection of a child during gestation or birth from the mother (vertical transmission)
examples
HIV
TORCH infections-
T= Toxoplasmosis
O= Others (syphilis, varicella zoster virus, parvovirus B19)
R= Rubella
C= Cytomegalovirus infection
H= Herpes simplex virus
Prodromal stage
initial appearances of symptoms
mild fever, myalgia, headache, and fatigue (somewhat nonspecific)
Acute Stage
maximum impact of the infectious process
inflammation and tissue damage (more specific)
Convalescent stage
progressive elimination of the pathogen
Exotoxin
proteins released by pathogenic bacteria
inactivate key cellular constituents (ex: diphtheria toxin inhibits protein synthesis)
many are super-antigens
Endotoxin
lipids and polysaccharides, not released (ex: lipopolysaccharides)
can induce clotting, bleeding, inflammation, hypotension, and fever (endotoxic shock)
Superantigen
induce excessive and nonspecific inflammatory responses
bind to the MHC of antigen-presenting cells and T-cell receptors
T cells are activated regardless of the antigen presented on MHC
Which of the following is an example of infection through fomites?
Question 1 options:
A student contracted COVID after talking to an infected friend.
A hiker has contracted amoebic dysentery after drinking water from a lake.
A man contracted syphilis after a sexual contact.
A woman has contracted Lyme disease after a tick bite.
A hotel guest contracted the flu after touching a contaminated button in an elevator.
