00:01
Hello and welcome to Enteric Bacterial Diseases.
We're going to explore a few
different kinds of bacteria that infect
the intestinal tract, and after you've
listened to this lecture, you'll know the
structure and virulence factors produced
by bacteria that cause enteric infections.
You will be familiar with the
pathogenesis and epidemiology of enteric
bacterial diseases associated with
Vibrio, E. coli, Shigella and Salmonella,
and you should know how to treat these
enteric bacterial infections. First, we're
going to look at a condition called
secretory or watery diarrhea, which you and
I have had for sure, maybe not caused
by bacteria, could be viral, but this is going
to be different from diarrhea we will
talk about later, which is bloody diarrhea.
Secretory watery diarrhea,
and we're going to look at members of the
Enterobacteriaceae and the vibrionaceae,
they're both gram-negative rods, two different kinds
of bacteria, one shown on the left,
the E. coli, and the one on the right the
vibrios. These bacteria are transmitted
to humans in contaminated food and water.
Contaminated with what? Fecal
material of course, either human or from
another animal. So in the end, it's all
about keeping your food or water clean,
which we seem to have problems doing.
01:40
These bacteria that cause watery
diarrhea adhere to the
epithelial cells of the gastrointestinal
tract. We showed in a previous lecture
a slide showing the structure of the wall
of the gastrointestinal tract; it's lined
with epithelial cells which you can see
at the bottom of this slide. And the bacteria
we're going to talk about sit on the surface
of this epithelium, they don't go
in, they don't invade, they're not invasive,
they sit on the top
and have their effects right there and they
adhere via their pili, and those
are composed of surface adhesins, and again
if you don't remember what pili
are, go back to the basic bacteria lecture.
What these bacteria do is they make toxins,
the toxins get into the epithelial cells
lining the gut and they cause problems,
they reduce sodium absorption and they increase
chloride secretion. They disturb
the homeostasis of sodium chloride balance
and that leads to water coming
out of the cells and there you go, there's
your watery diarrhea, caused by
toxins. Very easy to treat. You don't need
antibiotics. You just drink lots of
fluids.
03:02
Presumably water or perhaps some water-based
fluids with electrolytes would be
fine, but just need oral rehydration therapy
to replace what you're losing,
otherwise you get dehydrated and you'll have more
problems. Let's talk about