Term
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Definition
colonization of tissue by an organism
(pathogen has invaded & multiplied) |
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Term
| What is the difference between infectivity & pathogenicity? |
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Definition
infectivity = ability to colonize
pathogenicity = ability to cause disease |
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Term
| What are low-grade pathogens? |
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Definition
| opportunistic, only cause disease in immuno-compromised hosts |
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Term
True or False
Viruses are obligate intercellular organisms |
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Definition
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Term
| What are facultative organisms? |
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Definition
| can growth both inside & outside of cells |
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Term
| How does an organism gain entry to the body? |
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Definition
-natural passages (skin, resp tract, intestinal tract, urogenital tract)
-trauma
-direct inoculation |
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Term
True or False
The heart, bones, brain & muscle can only be infected via the blood |
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Definition
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Term
| What are the principal methods of spread of infection? (4) |
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Definition
-physical contact
-airborne infection
-food borne infection
-insect borne infection |
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Term
| What are the possible outcomes of infection? (3) |
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Definition
-invader dies (nonspecific/specific immune defense)
-invader survives, but no clinical signs of disease
-invader survives, multiplies, clinical disease |
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Term
| What aspects of the pathogen affect the outcome of infection? |
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Definition
| virulence & dose of exposure |
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Term
| What aspects of the host/environment affect the outcome of infection? |
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Definition
-status of nonspecific defense systems of the host (skin etc.)
-immune status of the host |
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Term
| What is a subclinical infection? |
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Definition
| pathogen elicits an immune response but no clinical signs are evident |
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Term
| How would you diagnose parasitemia? |
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Definition
| blood smears to ID the parasite |
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Term
| How would you diagnose viremia or bacteremia? |
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Definition
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Term
| What is transient bacteremia? |
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Definition
| small levels of bacteria are in the bloodstream being removed by the body |
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Term
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Definition
| bacterial toxins in the blood |
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Term
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Definition
| disease due to large levels of bacteria/toxins in the blood |
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Term
| What are the characteristics of clinical septicemia? |
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Definition
drop in blood pressure
high fever |
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Term
| What organisms are obligate intracellular parasites? |
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Definition
viruses
prions
rickettsia
chlamydia |
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Term
| Why do certain viruses only affect certain cell types? |
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Definition
| they have preference for specific parenchymal cells (which express different receptors) |
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Term
| What are the types of injury caused by viruses? |
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Definition
1. Virally-mediated cell necrosis
-cell injury & alteration of apoptosis pathways
2. Inflammatory & immune-mediated cell death
3. Virally-induced cell transformation & proliferation = neoplasia |
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Term
| How might viruses cause cell injury? |
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Definition
-viral replication inducing cell lysis
-inhibition of host DNA/RNA/protein synthesis
-damage to cell membranes |
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Term
| What are cytopathic viruses? |
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Definition
| viruses that cause cell death |
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Term
| What are inclusion bodies? What causes them? Where do they occur? Why are they useful? |
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Definition
-assembled viral particles or parts of viral nucleic acid synthesis
-viral replication in viruses & rickettsial infections
-in cytoplasm or nucleus
-can be used to ID specific viral infections e.g. rabies |
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Term
| Are viral hepatitis infections persistent or cytopathic? |
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Definition
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Term
| What virus causes cirrhosis? |
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Definition
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Term
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Definition
|
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Term
|
Definition
| which kind of cells a virus can bind to |
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Term
| HCV infection can lead to... |
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Definition
Acute hepatitis
Chronic hepatitis (cirrhosis)
Resolution |
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Term
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Definition
loss of lobular architecture of the liver
necrosis -> scarring -> nodular regeneration |
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Term
| How are viruses & apoptosis related? |
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Definition
some cells may undergo apoptosis to control viral infection
viruses can encode genes which impair apoptosis to promote persistent infection |
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Term
| A viral infection will show an ______ in lymphocytes and _____ in neutrophils |
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Definition
increase
decrease/no change |
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Term
| How are viruses & immune-mediated cell death related? (2 concepts) |
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Definition
-viral infection causes proteins to be expressed on cell surface
-CD8 lymphocytes recognize, induce cell-mediated immune response & lysis
-IFN is produced by CD4+ in the Th3 response
-IFN interferes with viral translation |
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Term
| What causes significant cellular loss in HBV? |
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Definition
| DC8+ T-cell mediated cytolysis of large numbers of cells |
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Term
| What does cytokine interferon (IFN) do? (3) |
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Definition
activates macrophages
enhance NK cell activity
antiviral effects |
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Term
| How do viruses cause neoplasia? |
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Definition
-infection causes some cells to be transformed
-transformed = immortal, grow indpendently of regulating signals (CANCER) |
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Term
| What is the damaging effect of Epstein-Barr Virus (EBV)? |
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Definition
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Term
| What are latent viral infections? |
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Definition
| viral genes are present in host cell but not expressed, may be reactivated later in life |
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Term
| How might a latent viral infection become reactivated? (3) |
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Definition
1. Fever/trauma etc causes fluid filled-vesicles to appear (inter & intra cellular edema)
2. Cells balloon & form intranuclear acidophilic viral inclusions
3. Adjacent cells fuse to form multinucleated prokaryons |
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Term
|
Definition
| inflammation of the oral mucosa |
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Term
| What is a major complication associated with viral infections |
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Definition
| secondary bacterial infections |
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Term
| How do filoviruses affect the body? |
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Definition
-highly cytopathic
-cause fever, muscle pains, anorexia, rashes, abdominal pain, hemorrhage |
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Term
| What are the facultative intracellular organisms? |
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Definition
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Term
| The cellular response to viruses, Rickettsia & Chlamydias is typically.... |
|
Definition
mononuclear
(lymphocytes, plasma cells, macrophages) |
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Term
|
Definition
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Term
|
Definition
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Term
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Definition
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Term
| HOw are rickettia transmitted? |
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Definition
| require arthropod vectors e.g. fleas ticks mites |
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Term
| What differentiates a prion from a virus? |
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Definition
| prions do not have nucleic acid (RNA or DNA) |
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Term
| What are infectious prion proteins? What do they do? How are they transmitted? |
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Definition
-abnormal forms of normal proteins that induce changes in conformation of host proteins
-cause accumulation of proteins in tissues (esp brain)
-contagious, familial or sporadic |
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Term
| What do abnormal prion proteins (PrPsc) cause? |
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Definition
spongiform encephalopathies (vacuolar degeneration in the brain)
-accumulation = dysfunction of brain tissue = neuronal loss |
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Term
| Prion infection is characterized by... |
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Definition
| progressive loss of function |
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Term
True or False
Prions induce an inflammatory reponse |
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Definition
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Term
| What are opportunistic bacteria? |
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Definition
| bacteria which are beneficial in normal circumstances, but will flourish if host is immunosuppressed or they go to a part of the body where they aren't supposed to be |
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Term
| How can bacterial infections be treated? |
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Definition
Bacteriostatic agents - inhibit growth/multiplication
Bactericidal agents: kill bacteria |
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Term
| How do bacteria cause cell/tissue injury? (3) |
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Definition
1. Adhering to host cells
2. Releasing toxins
3. Producing local vasculitis |
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Term
| What are bacterial adhesins? Give an example |
|
Definition
surface molecules that bind to host cells
-cocci |
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Term
| How do gram positive & gram negative cocci bind? |
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Definition
Gram positive:
-fibrillae bind to fibronectin on host surface
-M proteins prevent phagocytosis
Gram negative
-fimbriae (pili) allow gene exchange & mediate adhesion |
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Term
| What do bacterial endotoxins do? |
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Definition
-generalized peripheral vasodilation -> shock
-endothelial injury & activate coag cascade -> acute resp distress & DIC
-cytokine release -> acute phase response |
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Term
| What do locally-acting bacterial exotoxins do? (3) give examples |
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Definition
Locally-acting: enzymes which break down compounds & facilitate tissue invasion
Staphylococcus aureus
Clostridium perfringes |
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Term
| What do remotely-acting bacterial exotoxins do? Give some examples |
|
Definition
-induce formation of antibodies
-secreted by bacteria, carried by bloodstream elsewhere in body
Staphylococcus aureus - Toxic Shock Syndrome
Clostridium tetani - tetanus
Clostridium botlinum - botulism |
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|
Term
| What is necrotizing fasciitis? |
|
Definition
-rapid necrosis of subcutaneous issues extending into deep fascia
-secondary gangrene
-causal bacteria secrete exotxin
-often starts due to some minor trauma/surgical pound |
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Term
| What does the exotoxin of clostridium tetani do? |
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Definition
| -travels from wound to spinal cord, causes violent muscle spasms |
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Term
| What does the clostridium botulinim exotoxin do? |
|
Definition
| -blocks release of neurotransmitters leading to flaccid paralysis |
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Term
| What do enterotoxins do? Give some examples |
|
Definition
exotoxins which affect intestinal mucosal cells (enterocytes)
-attach to gut mucosal cell receptors, cause structural or functional diarrhea
Vibrio cholerae
Toxigenic escherichia coli |
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Term
| What is food poisoning? What are the two categories? Give an example of each |
|
Definition
acute gastroenteritis due to bacterial toxins
Infection type
-bacteria multiple in contaminated food, produce toxins in the bowel
e.g. Salmonella enteritidis
Toxin Type
-bacteria produce toxins in the food
e.g. Satphylococcal food poisoning |
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Term
| What will cause more rapid clinical signs, infection type of toxin type food poisoning? |
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Definition
|
|
Term
| What is bacterial local vasculitis? |
|
Definition
-highly virulent bacteria cause thrombosis of small blood vessels leading to ischemic necrosis in the area
-toxins can also cause vascular injury |
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Term
| What are the characteristics of the body's response to bacterial infection? |
|
Definition
Acute inflammation
-lots of neutrophils present
Suppurative inflammation
-liquefactive necrosis, pus, abcesses |
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Term
| When would suppurative inflammation in response to bacterial infection be especially likely to occur? |
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Definition
| where drainage & resolution of acute inflam is inhibited by anatomical factors |
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Term
| What is hardware disease? |
|
Definition
metal trapped in reticulum punctures wall, will eventually penetrate pericardial sac
-severe fibrinopululent inflammation results (fibrin & pus)
-affects heard & lung function |
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Term
| What are Koch's postulates? Why do we use them? |
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Definition
Used to determine causal bacteria of a disease
1. causal organism can be found in the disease lesions & isolated in culture
2. secondary introduction of the isolated organisms causes lesions in experimental animals
3. the organism can be recovered from the experimental animal |
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Term
| What is require for fungi to grow? |
|
Definition
| warmth, high humidity, oxygen |
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Term
| What is the association between antibiotics & fungi? |
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Definition
| antibiotic overuse destroys 'good' bacteria which limit fungal growth |
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Term
| How do fungi cause tissue injury? |
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Definition
-induce DTH hypersensitivity responses to fungal antigens
-may see granulomatous lesions in the tissue
-some directly invade small vessels causing thrombosis & necrosis of nearby tissue |
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Term
| What are systemic fungal diseases? Give some examples |
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Definition
-diseases which affect deeper tissues
e.g. histoplasmosis, coccidioidomycosis |
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Term
| What are superficial fungal diseases? Give some examples |
|
Definition
-diseases which affect superficial tissue
Dermatomycoses (ringworm/athletes foot)
Candidiasis |
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Term
|
Definition
disease caused by opportunistic candida bacteria
-vaginitis, espophagitis, chronic & subcutaneou candidiasis etc |
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Term
| What is a definitive host? |
|
Definition
| the host of the adult (mature, reproducing) form of a parasite |
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Term
| What is an intermediate host? |
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Definition
| host of immature form(s) of a parasite |
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Term
| What are the characteristics of inflammatory reactions to parasitic infectoin? |
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Definition
-eosinophils
-granulomatous inflammation |
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Term
| How are protozoa transmitted? |
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Definition
| via insect vectors or by ingestion |
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Term
|
Definition
| protozoal infection of the parasite Plasmodium |
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Term
| How do protozoa cause disease? |
|
Definition
1. Sporozoites enter blood stream, undergo asexual repro
2. Sporozoites multiple forming lots of merozoites
3. Merozoites are released, infect RBCs
4. Merozoites form trophozoites (asexual repro) or produce gametes which will infect a mosquito |
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Term
| What are the clinical features of malaria and what causes them? (4) |
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Definition
-spikes of chills/fever as mew merozoites are released every 48hrs
-hemolytic anemia (parasites destroy RBCs)
-RBCs release brown pigment (dark liver, lymph nodes, bone marrow)
-phagocytic defense leads to hyperplasia of mononuclear phagocytes leading to an enlarged spleen |
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|
Term
True or False
Helminths are opportunistic organisms |
|
Definition
|
|
Term
| What are the types of helminths? Do they require intermediate hosts? Give examples of each |
|
Definition
Nematodes (Roundworms)
-no intermediate host
-pinworms, hookworms, roundworms
Cestodes (tapeworms)
-intermediate hosts eg. beef, pork, fish
-rarely cause disease in human hosts
Trematodes (flukes)
-require int host e.g. snails
-schistosomiasis (infect bladder, cause hematuria) |
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Term
| Why are arthropods a concern? |
|
Definition
they act as vectors of disease (viral & bacterial)
e.g. lice, fleas etc. |
|
|
Term
| How do arthropods act as vectors? |
|
Definition
Mechanically
-picks up infecting agent, deposits it on foods or passes on by contamination of biting mouth parts
Biologically
-arthropod is essential in completing the life cycle of the infecting agent |
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