Invasive gram-neg bacterial pathogens of GI tract Flashcards
Enterobacteriaceae and Vibronoaceae are both prolific colonizers of what?
mucosal surfaces
what is a mucosal surface?
Surface that interacts with air that has associated glands for secreting mucus.
what are the defenses of the mucosal surface?
- Innate immunity
- Adaptive immunity
- Nonspecific barrier defenses
transmission of gram-negative mucosal pathogens: via what pathways?
the “seven F’s”
feces to mouth
what are the “7 F’s”?
Feces Food Fluids Fingers Flies Fomites Fornication
what is the lowest range of inoculum size? (Shigella dysenteriae)
50-100 organisms
what are the natural barrier defenses for gram-negative pathogens?
A) secretory substances
B) anatomical and physiological
barriers
C) indigenous microbiota
what is the pH level of the gastrointestinal tract?
1-2 all the way up to 9
how does a Lysozyme (a.k.a muramidase) destroy a bacteria?
cleaves beta 1,4 glycosidic linkages between NAM and NAG
-only works on exposed murien (gram positive)
what is lactoferrin’s main function?
sequester iron
how does Cathelicidin work toward destroying a microbe?
Disrupts bacterial membranes of BOTH gram - and gram + bacteria
What do Defensins create on the target microbe?
pores
what are the 2 types of Defensins? where are they produced?
Alpha - produced by neutrophils and paneth cells (intestines)
Beta- produced by epithelial cells
How do pathogenic bacteria overcome these innate barrier defenses?
1) Acid resistance
2) Fimbriae/Pili
3) Bacterial structures
________ are an Important Component of Mucosal Immunity
Macrophages
Activation of pattern recognition receptors on macrophages also initiates the _______ _________
Inflammatory response
Which TLR will be most important for identifying gram-negative bacteria?
TLR4
Inflammatory cytokines, such as TNF-α can disrupt the _________ ______ between epithelial cells
Tight junctions
the Four species of Shigella are distinguished by what?
The O antigen
T/F: the Inoculum size of Shigella is very small
True
_____ _______ facilitates survival of Shigella through the stomach
Acid resistance
where will Shigella multiply and colonize?
in the Colon
Shigella microbes will travel through the mucosal surfaces, eventually entering what type of cell?
M cells
how does Shigella enter the M cells?
using the outer membrane protein “invasion plasmid antigens”
once it has entered the M cells, where is it released?
into the lamina propria- causes inflammatory response
what response to Shigella actually causes illness?
inflammatory response as a result of macrophage activity
Intracellular spread of Shigella facilitated by _______, an ATPase that causes ________
IcsA
actin polymerization
what develops when invaded Shigella cells die and slough off?
Ulcer
what immune cell can be found in the stool of people infected with Shigella?
Neutrophils
All species of Shigella will induce an _______ ______ with leukocytes in the stool
inflammatory diarrhea
which Shigella species induces a watery stool?
S. sonnei
why is S. dysenteriae (Shigella) different from other forms of the genus?
it produces SHIGA TOXIN
what does Shiga toxin do?
kills intestinal epithelium and endothelial cells
disrupts Na absorption
Salmonella causes what 2 main diseases?
A) Gastroenteritis
B) Typhoid fever
which species of Salmonella causes typhoid fever?
Salmonella typhi
how is Salmonella transmitted?
fecal-oral transmission
can be between human or animal
T/F: a relatively small inoculum is required for Salmonella
False- large inoculum required
Salmonella is more _____-sensitive than shigellae
acid
in Salmonella- a low pH induces the expression of at least 40 proteins found on what?
pathogenicity islands on large virulence plasmids
when Salmonella approaches a host cell surface, it causes the increase of what within the cell?
Calcium
Ca2+
the forced uptake of Salmonella into the host cell is known as what?
Microbe-directed phagocytosis
unlike Shigella, Salmonella remains within ________ for many hours after entering
cell vesicles
when salmonella is released to the lamina propria, what does it induce?
a loss of Na and Cl from the host cell
Salmonella typhi will survive and grow within the _______
macrophages
Salmonella typhi will travel from the gastrointestinal tract into the ____ ______
lymphatic system
Salmonella typhi cannot survive in a _______ reservoir, meaning its strictly a what?
- cannot survive in an animal reservoir
- strictly a human pathogen
carriers of Salmonella typhi can often be _____
asymptomatic
-they have colonized gall bladders
what is a unique property of the Salmonella strains that cause typhoid fever?
they multiply in macrophages in the:
A) liver
B) spleen
C) bone marrow
Shigella and Salmonella are both invasive, so both are able to do what?
invade into the intestinal epithelial cells
both can invade host cells
differences between Shigella and Salmonella:
1) Inoculum size (i.e., acid sensitivity)
2) Bacteremia (only Salmonella)
3) Species that cause severe disease are very dissimilar.
Salmonella and Shigella species both cause what symptoms upon infection?
Large Intestine Small Volume of Stool Bloody Stool Leukocytes in Stool Tissue Ulcerations
