Chapter 15 Micro Flashcards
What is pathogenicity?
The ability to cause disease, a property of the organism that it either has or lacks
What is virulence?
The extent of pathogenicity, a measurement of the degree of pathogenicity that it can be assessed
What are mucous membranes?
lining respiratory tract, gastrointestinal tract, genitourinary tract, conjunctiva
What are the portals of entry related to skin?
hair follicles, sweat glands, surface
What are the portals of entry related to the parenteral route?
(not parental) – due to penetration or injury
regardless of anatomical site of entry
Preferred portal of entry
“preferred” by the organism, not by us
What is ID50?
Infectious dose for 50% of the test population
What is LD50?
Lethal dose (of a toxin) for 50% of the test population
What is adherence?
Adhesins or ligands on the microbe bind to receptors on host cells
Ex: glycocalyx, fimbriae, M protein
What are biofilms?
-communities of adherent microbes
-an aggregate of microbes stick to each other
and to a substrate (surface)
-adhere to most surfaces with organic matter, a mix of polysaccharides and proteins
-involved in 65% of human bacterial infections
What are capsules?
- capsules are not required but increase virulence of bacteria that have them
- preventing phagocytosis by immune system cells
- Can be targeted by antibodies
What is an M protein?
resists phagocytosis
-Strep. pyogenes
What is opa protein?
inhibits T helper cells
-Neisseria gonorrhoeae
What is mycolic acid?
(waxy lipid) resists digestion
Mycobacterium tub.
What are exo enzymes?
enzymes that work outside the bacterium to increase virulence
What is coagulase?
Coagulates fibrinogen
What are kinases?
Digest fibrin clots
What is hyaluronidase?
Hydrolyzes hyaluronic acid
What is collagenase?
Hydrolyzes collagen
What are IgA proteases?
Destroy IgA antibodies
What are invasins?
- Type of penetration of the host cell cytoskeleton
- Salmonella alters host actin to enter a host cell
- causes membrane ruffling
How does penetration into the host cell occur?
Use actin to move from one cell to the next
What does antigenic variation do?
- Alter surface proteins
- Surface proteins are encoded by genes that change
How do pathogens damage host cells?
- deplete host’s nutrients
- cause direct damage
- synthesize toxins
- cause immune reactions
What are siderophores?
siderophores chelate host’s iron and allow the bacteria to take it up
What is direct damage?
disrupt host cell function
produce problematic waste products
action of toxins
Of the ~220 known bacterial toxins, about 40% cause disease by damaging eukaryotic cell membranes
Many toxins, such as botulism toxin (botox) is a neurotoxin, that is they target and inhibit the function of neurons.
What are toxins?
Substance that contributes to pathogenicity
What is toxigenicity?
Ability to produce a toxin
What is toxemia?
Presence of toxin in the host’s blood
What is a toxoid?
Toxoid: Inactivated toxin used in a vaccine
What are antitoxins?
Antibodies against a specific toxin
What are exotoxins?
Toxins target specific structure on or in the host cell
What are membrane disrupting toxins?
Lyse host cells by making protein channels in the plasma membrane
What are some examples of of membrane disrupting toxins and what do they do?
- Leukocidins: kill phagocytic leukocytes
- Hemolysins: destroy erythrocytes
- Streptolysins: lyse RBC
- Disrupt phospholipid bilayer
What are superantigens?
- Cause an intense immune response due to release of cytokines from host cells stimulating proliferation of T cells
- this reaction disables the host immune system
- Symptoms: fever, nausea, vomiting, diarrhea, shock, and death
What is diphtheria toxin?
Corynebacterium diphtheriae lysogenic phage caries tox gene tox encodes an A-B exotoxin causes diptheria, an upper respiratory tract disease can cause severe skin lesions part of the DPT vaccine
What are erythrogenic toxin?
Streptococcus pyogenes
superantigen
damages plasma membranes of capillaries in skin
causes Scarlet Fever, characterized by red skin rash
What is botulinum toxin?
Clostridium botulinum
A-B exotoxin
neurotoxin, inhibits acetylcholine
acts at the neuromuscular junction, preventing transmission of impulses from the nerve to the muscle, flaccid paralysis
What is tetanus toxin?
Clostridium tetani A-B exotoxin neurotoxin causes uncontrollable muscle contractions “lockjaw”
What is vibrio enterotoxin?
Vibrio cholerae A-B exotoxin enterotoxin B subunit binds epithelial cells causes cells to secrete fluids and electrolytes severe diarrhea
What is staph enterotoxin?
Staphylococcus aureus
superantigen
toxic shock syndrome
What are endotoxins?
outer portion of cell wall gram neg
- LPS
- cause macrophages to make cytokines
LAL assay
Limulus amoebocyte lysate assay
detects very small amounts of endotoxin
amoebocyte (blood cell) lysis produces a clot
Endotoxin causes lysis
What are portals of exit?
Earwax, blood, skin flakes, feces, tears, secretion, saliva
Pathogenesis of SARS COV 2
SARS-CoV-2 infects the upper respiratory tract (sinuses, nose, and throat) and the lower respiratory tract (windpipe and lungs).
Its receptor ACE2 is abundant in type II alveolar cells of the lungs.
As alveolar disease progresses, respiratory failure and can follow.
It is not clear whether SARS-CoV-2 is able to infect and cause pathology in the nervous system.
The virus also affects gastrointestinal organs. ACE2 is abundant on cells of gut epithelium.
The virus can cause acute myocardial injury and chronic damage to the cardiovascular system.
A common cause of death is complications related to the kidneys.
What are cytopathic effects of viruses?
transformed cells, loss of contact inhibition
What is viral pathogenesis?
cytopathic
shut-down of host macromolecular synthesis, cell lysis
lysozymes - triggered inside cells, consume from within
inclusion bodies - aggregates visible inside cells
syncytium - fusion of cells, create single cells with multiple nuclei
apoptosis (programmed cell death)
non-cytopathic (change cell function, behavior)
transformation
inhibition of apoptosis (programmed cell death)
immortalization, loss of contact-inhibition
can lead to cancer
immune response
inflammation, interferon
auto-immunity
What is the action of an A-B exotoxin?
1.bacterium produces and releases exotoxin
2. B binding component of exotoxin attaches to the host cell receptor
3. A-B exotoxin enters the cell by endocytosis
4. A-B exotoxin enclosed in pinched off portion of plasma membrane during pinocytosis
5. A-B components of exotoxin sep. The A component alters cell by inhibiting protein synthesis
B component is released from host cell
What are some diseases passed via the fecal oral route?
Poliomyelitis Hep A Rotvirus Shigellosis Typhoid fever Cholera C. diff
