EXAM 4 P4 Flashcards
LD50
lethal dose 50
measure of virulence
is the number of pathogen cells required to kill 50% of infected organisms
is dependent on the pathogen species and strain, and the host species, age, sex, physical condition, and how it’s introduced
streptococcus pneumoniae
highly virulent organism
salmonella typhimurium
moderately virulent organism
virulence factors
produced by the pathogen to increase its ability to cause disease
capsule
extracellular polysaccharide that helps with adherence and invasion
inhibits phagocytosis by innate immune response
fimbriae
help with adherence
siderophores
help with iron activation
toxins
either a protein or non-protein
only non-protein toxin is endotoxin
protein toxins include exotoxins and enterotoxins
hemolysin
exotoxin (cytotoxin)
has the ability to lyse red blood cells
blackening reaction with the release of iron
cells can often lyse other host cells, causing tissue damage and disruption of blood flow, making it more hospitable for growth
some form pores in the mem
lipase
exotoxin (cytotoxin)
breaks down lipids
if enough lipids are cleaved, the cell may break open
neurotoxins
exotoxin (cytotoxin)
released by a pathogen that has side effects on neurons in the host body.
C. botulinum toxin
blocks nerve stimulation of muscle contraction
botulism
extremely potent and deadly
first symptom is not being able to contract the muscles. they become flaccid, even the diaphragm, making you unable to breath.
medical use of C. botulinum toxin
Botox injections
C. tetani toxin
causes constant nerve stimulation of muscle contraction
tetanus (lockjaw)
all muscles start contracting and can’t move, so you’re unable to open your mouth
will essentially curl up in the fetal position
diaphragm contracts and kills you
cholera toxin “AB-form toxin”
enterotoxin
causes extreme diarrhea where you essentially die of dehydration
in a normal body, the lumen is lined by epithelial cells where nutrients are passed through to the blood. they pick up sodium irons and transport them to the blood.
with cholera toxin, it binds to these cells and part of it enters the host cell, functioning as an adenylate cyclase (takes ATP and converts it). water follows and in the intestines you suddenly have water, aka DIARRHEA.
what does AB-form toxin mean
it’s made of 2 proteins
the B protein binds to the host cell surface
the A protein enters the host cell and affects metabolism
endotoxin
LPS in the gram negative outer membrane
it’s not intentionally produced to make the host sick. it’s just part of the cell
LPS is one of the things the immune system recognizes as infection.
it can cause fever, diarrhea, and inflammation
characteristics of exotoxins
are excreted
have specific binding and effects on the cell
highly toxic, sometimes fatal
highly immunogenic; stimulate production of antitoxin
does not produce fever
characteristics of endotoxins
LPS released on cell lysis
general effects (fever, diarrhea, vomiting)
weakly toxic, rarely fatal
poor immunogen; immune response not sufficient to neutralize toxin
no toxoid potential
pyrogenic; often induces fever in the host
streptococcus
gram positive cocci in chains
common member of normal flora of the upper res tract
pathogenic strains produce capsules
infections related to streptococcus
pharyngitis (strep throat) otitis media (ear infection) mastitis (mammary glands) impetigo (sores common in small children) erysipelas (very red skin)
scarlet fever
redness over a wide area of the body
rarely, particularly virulent strains cause necrotizing fasciitis (flesh eating bacteria) that breaks down tissue
you lose blood flow and oxidation of the tissue, leading to skin grafts or amputation
rheumatic fever
autoimmune reaction against heart valves due to similar antigens
shows up months after the initial infection
produce some protein similar to one in the heart valve, confusing recognition
Neisseria meningitidis (B)
gram negative diplococci
bacteremia is invasion of the bloodstream. toxins cause coagulation and interrupted blood flow to extremities
tissue starts to die (necrosis)
often causes amputation of the limbs. once it’s dead it can’t be saved
Neisseria meningitidis (M)
meningitis is the inflammation of the membranes around the central nervous system
caused by a variety of bacteria and viruses.
can get into the spinal cord and brainstem, leading to death
progresses rapidly with 10% death even with treatment
common in college student populations
borrelia burgdorferi
gram negative spirochete
grows in many wild animal mammals (mice and deer) without clear disease
transferred from reservoir wild animals to humans by deer ticks. ticks must be on humans for over 24 hours to pass the bacteria.
Lyme disease
Lyme disease
common in the northeast and upper mid-west
increasing incidence in the past 20 years
variety of factors contribute to this: increased deer populations, increased reporting, and increased human/tick contact
lone star tick
progression of being bit by the lone star tick
no toxins, just inflammation (endotoxin).
initial symptom is erythema migrans (rash) spread form bite over several days.
headaches, chills, and fatigue are common. treated with antibiotics
if left untreated, chronic symptoms can progress
arthritis as bacteria invades the joints
invasion of the neural system (palsy, facial tics, weakness)
chronic symptoms are dye to residual peptidoglycan since BB has novel pg. structure.
