Module 15 Flashcards
which of these are Gram + spore forming rods?
a - corynebacterium diphtheria
b - bacillus anthracis
c - clostridium perfringens
d - listeria monocytogenes
e - b & c
e - b & c
what bacteria is a Gram - rod that is found in intestines of humans and animals and widely distributed on plants, in soil and water
E. coli
what are the major pathogens of Gram - enteric rods
- Escherichia
- shigella
- salmonella
- vibrio
what can be caused by normal flora strains of E. coli that escape from the intestinal tract and colonize other body sites
- UTI
- invasive disease (septicemia, neonatal meningitis)
what is in the normal intestinal flora and is the leading cause of both community-acquired and nosocomial infections
E. coli
what can be caused by “new” strains of E. coli that have acquired additional virulence factors
gastroenteritis (diarrhea)
what is the transmission of E. coli
- trauma
- immune suppression
- fecal-oral spread
what are the virulence factors of E. coli
- LPS endotoxin (inflammation)
- enterotoxins
what are examples of enterotoxins
- plasmid coded enterotoxins
- heat-liable toxin (LT)
- heat-stable toxin (ST)
what causes the activation of adenylate cyclase leading to fluid secretion and diarrhea and is related to the cholera toxin family
heat=liable toxin (LT)
what is a small peptide that increases fluid secretion and diarrhea
heat-stable toxin (ST)
what is the colonization and inflammation of a UTI
- bladder (cystitis)
- invade and replicate in epithelial cells
- ascends to kidney (pyelonephritis)
- spread to bloodstream
what is the main cause of neonatal meningitis
vaginal normal flora E. coli colonizes the infant at birth during passage through the birth canal
90% of vaginal normal flora E. coli express ___
capsule
how does systemic inflammation or septic shock occur
stimulated by large amounts of endotoxins in intestinal E. coli that crosses epithelial surfaces and invades the bloodstream of a patient with immune impairment or mechanical damage
what bacteria is closely related to E. coli but is NOT normal flora
shigella
___ causes classical bacterial dysentery
S. dysenteriae
T/F shigella involves intracellular growth
true
what is a virulence factor of shigella
plasmids that encode proteins for attachment / entry into intestinal epithelial cells
what population is bacterial dysentery most common in
pediatric
what is shigella’s exotosin
shiga toxin
what does shiga toxin cause
transfer of lysogenic phage chromosome to E. coli making it lethal and inhibiting protein synthesis thus damaging endothelial cells in the intestinal mucosa and systemically in kidneys
what is colonization of large intestines with invasion and replication within colonic epithelial cells causing erosion of the large intestine epithelia
bacterial dysentery
what are signs and symptoms of shigella
- cramps, painful straining, bloody mucoid discharge
- large numbers of leukocytes & RBCs in stool
- fever
what is the primary reservoir of salmonella
intestinal tract of animals (birds, cattle, pet reptiles, etc.)
how do humans become infected with salmonella
ingestion of contaminated food or water or feces from infected animals
what are the 2 forms of disease that salmonella can cause
- gastroenteritis
- typhoid fever
what specific bacteria causes gastroenteritis
s. typhimurium
what specific bacteria causes typhoid fever
s. typhi
salmonella has ___ survival and growth & remains only at the ___
intracellular, intestinal epithelium
what is found only in S. typhi
Vi capsule
what does S. typhi lack
exotoxins/enterotoxins
what are the 2 current typhoid fever vaccines
- purified Vi capsule polysaccharide
- live attenuated Ty 21a strain
what are the visible characteristics of vibrio cholera
curved, Gram - rods with single polar flagella
what is the preferred environment of vibrio
surface waters worldwide that grow over wide ranges of temperatures with high pH
what is the exotoxin of V. cholerae
cholera enterotoxin
what does cholera enterotoxin do
chemically modifies adenylate cyclase and stimulates fluid secretion in intestinal epithelial cells
what are the clinical manifestations of cholera
rice water stool, dehydration, electrolyte imbalance
caused by colonization of mucosal surface of the upper small intestine
what is the treatment for cholera
fluid replacement
what is the recent cholera vaccine
Vaxchora
how does Vaxchora work
oral, live attenuated V. cholerae 01 with toxin lacking A subunit that triggers protective mucosal Ab to whole bacterium and to the toxin B subunit
is there a vaccine for cholera?
a - yes its a live strain of vibrio
b - yes its a subunit of vibrio toxin
c - no not yet
d - yes its a closely related strain of salmonella
a - yes its a live strain of vibrio
what is the Vi capsule that is important in Typhoid Fever?
a - capsule seen only on S. Typhi bacteria
b - important in using live Salmonella as a vaccine
c - it is antiphagocytic
d - all of these
d - all of these
which is NOT a toxin E, coli can acquire by horizontal gene exchange and become dangerous?
a - shiga toxin
b - heat stable toxin
c - heat liable toxin
d - LPS endotoxin
e - all of these are E. coli toxins
e - all of these are E. coli toxins
