Gut --
moist, solids -- makes for a much higher bac load than Resp system, nowhere
is it sterile
Stomach -- HCl, shift in flora
Upper Alimentary -- mouth physiology to moisten
& break down food
mucus -- to protect lining of mouth
1. buffers mouth [neutralizes acids]
2. saturated with calcium and phosphate ions. Crystalize [slows advance of caries]
3. antimicrobial substances: lysozyme, lactoferrin, IgA [spec for bugs already encountered, IgA binds to bug specifically and to mucus, IgA res. digestion]
On the other side:
amylase [more to follow]
1. local immune system [tonsils] STRONG -> protection
2. normal flora
Streptococci
tongue -- S. salivarus
cheek -- S. mitis all aerobic
teeth -- S. sanguis
deep cleft --[anaerobic] Bacteriodes + Fusobacterium
plaque
1. starts with S. sanguis sticks to pellicle [a thin protein film]
2. bac film of S. sanguis -- followed by Hemophillus & Veillonella &
Neisseria & Rothia & Actinomyces
plaque is colonized Strep mutans, (requires teeth)
1. binds together the plaque
2. acids from sugars lowers pH 2
units ---eats through enamel
exposes dentine, dental caries
plaque near gums --> inflammation: gingivitis (gingivums
= gums, soft tissue)
-->prolonged--scarring, gum recede, loose teeth, tooth loss
Streptococcus Viridans group
bacterial endocarditis
Vincent’s angina a.k.a. trench mouth, a.k.a. acute
necrotizing ulcerative gingivitis=ANUG is an ulceration of gums.
Fusobacterium & Treponema [spriochete]
Fungal -- Candida albicans is a problem in immunocompromised -- superficial,
painful, THRUSH-infection of mucous membranes
Viral infections of the mouth
Herpes simplex, an enveloped DNA virus
lytic infection of mucous forming epithelial cells / cold
sore
latent, non-lytic infection of neurons
Mumps -- salivary glands -- inflammed
-- ssRNA, paramyxovirus spreads throughout the body, central nervous system,
testes
scarring and loss of function result
virus has fusion protein--to fuse cells
necessary to have killer T cells to eradicate mumps
The Stomach
Helicobacter pylori -- critical in peptic ulcer
gram -- motile rod, sheathed completely
Urease -- ammonia which neutralizes acid
Mucinase --
adhesion molecules bind to edges "between" cells
1. Hemolytic toxins --> inflammation, serum, bleeding
2. Hemolysin -- hemin (by degrading hemoglobin)
all this results in inflammation & leak of acid --> peptic ulcer
mix antibiotics with bismuth salts
2006 Nobel prize--more defenses!
Lower Gut
duodenum --> small intestine --> large intestine or colon
Why fewer bac in small intestine?
mouth amylase--starches
stomach pepsin--proteins
small intestine--few normal flora
include associated organs and their functions:
1. gall bladder and liver--bile salts
2. pancreas--proteases
--lipases
Food Chyme
Colon--resorb water
lubricate for excretion
slower movement forward
300 species of bacteria
1/3 dry weight of feces is bacteria
N ormal flora:
Bacteriodes
Enterbacteriaccea
E. coli
Klebsiella
Proteus
disease
Shigella
Salmonella
Bacteriodes--anaeorbic
gram neg
Clostridium difficile
Diarrheas
1. destroy lining
2. induce lining to secrete fluid
Cholera
Vibrio cholerae G- motile curved rod
Cholera toxin --
causes lining cells to secrete vast amounts of fluid,
L/hr water + electrolytes
"rice-water" stools
AB toxin binding -- GM1
gangliosides-->ATP-->cAMP-->secretion--water, sodium, potassium, bicarbonate
actives adlenyl cyclase
replacement of the intestinal cells themselves limits the infection
example:
V cholerae el tor
E. coli
a pathogen with the addition of toxins, invasion factors & adhesion factors
diarrheas caused by different E coli:
entertoxingenic ETEC
toxin ~like~choleratoxin diarrheas
enterohomorrhegic EHEC
Verotoxin (kills a tissue culture line called Vero cells)has acquired a Shigella
-[like] toxin--transfer
bloody diarrheas
enteroinvasive EIEC
invades gut wall on a plasmid
bloody diarrheas
enteropathogenic EPEC
stick to brush border, form channels
in mb to deliver toxin
enteroaggregative EAggEC
clumps stick to gut surface
diarrheas in infants
ETEC-
adhere [do not invade]
causes traveller's diarrhea
has a cholera toxin-like toxin [heat labile]
and a 2nd diarrheal toxin [heat stable]
bac. dysentery --
watery diarrhea + mucus + blood + pusreal gut
[A=ETEC B and C are EPEC]
Shigella
1. Shigella toxin
Shigella adhere to colon -- invade & survive in macrophages. -->escape
into cytoplasm
2. invasion properties are necessary to cause disease
Gastro enteritis -- inflammation of the gut [colon]
Campylobacter jejuni -- less 1,000 organisms can cause disease
Salmonella enteriditis -- eggs
All enterobacteria make endotoxin, specifically LPS
LPS stimulates macrophages, platlets, smooth muscle, endothelial cells
LPS is a pyrogen [fever-causing agent] and it activates complement.
Salmonella
S. typhi -- Goes to Peyer’s Patches
prevents phago-lysosome fusion in macrophages
spreads everywhere: brain, spleen, bone marrow, joints, lungs, liver, gall bladder,
blood
generalized effects = typhoid fever
Human reservoir ONLY, attaches small intestine
bac toxins
immune response: makes cytokines
gall bladder survival of S. typhi results in shedding of S. typhi; thus a carrier
can transmit disease but no longer has symptoms Ex: Typhoid Mary ....or maybe
Ella
Clostridia--anaerobic, G+ spore forming rods
C. per -- in gut makes enterotoxin,
travelling through acid in stomach
induces stress response genes and the toxin --is one of those stress
genes
enteric toxinoses
C. botulinum -- adults -- preformed toxin
infant botulism -- in foods like honey
if reheated [15 minutes] toxin -- heat sensitive
mode of action
toxin --> bloodstream --> nerves
Three toxins:
botulinal toxin
C2 toxin -- diarrhea as cholera toxin
C3 toxin
Botulinal toxin is a zinc -dependent protease
synaptobrevens broken up, limp paralysis
on a plasmid. This has led to "natural" transfer to C. butyricum
Botulinal toxin
surface of neuron -- binding
zinc-dependent protease -- acts on acetylcholine release
[so it affects the cholinergic nerves the excitory synapses]
the zinc-dependent protease digests
synaptobrevins -- no nervous signal
limp paralysis = flaccid
Typical contamination scenarios 1, 2
Common symptoms and the bugs in food which cause them
Tetanus -- causes stiff paralysis = spastic
C. tetanii --
using same enzymatic activity in its toxinas botulinum toxin-- acts on brain
Why different pathology if same toxin?
1. specificity for different target cells
(inhibitory synapses for tetanus [GABA, gly) or
different parts of synaptobrevins
2. synaptobrevins themselves are different now known--cuts
at different sites.
C. difficile
C difficile --
1. enterotoxin -- inflammation & diarrhea
2. cytotoxin -- death of lining cells of the gut.
Food Poisoning -- toxins enterotoxin
1. preformed --> Stapholoccus aureus -- heat stableStaph aureus endotoxins
SEA, SEB, c-e
+ superantigens
super antigens --> T cells --> cytokines --> damage
S.EA --> E
SEA, SEB, etc.
2. made in passing
More Spore formers
Bacillus cereus -- rice, meat, vegetables
1. heat sensitive, diarrhea = c.t.
2. heat resistant -- smooth muscle contraction, cramps, nausea, vomiting
Fungal
1. ergot poisoning -- St. Anthony’s fire
contaminate bread --> failure nerve impulses & vascular collapse
2. afflatoxins -- Aspergillus
liver disfunction --> chickens <-- destroy the flock if positive
most recently strawberries from California
3. hallucinogenic fungi
Viral
diarrheas: resistant to drying, acid, detergent
1. rotaviruses -- infantile diarrheas, 5-8 days of symptoms
2. caliciviruses -- ex: Norwalk viruses and astroviruses
both infect gut lining, symptoms for 24-48 hours
Protozoa
Giardia lamblia-- also known as--
G. intestinalis-- giardiasis
entry feco-oral; organism is sealed, acid resistant, quiescent forms -- cysts
(also true for E. Histolytica -causes dysentery)
Giardia pass through stomach:
lower gut -- cyst opens --> active feeding forms
flagellate bug attaches by adhesion disks
Interferes:
1. nutrients + inflammation
2. water secretion balance --> diarrhea
Entamoeba histolytica -- amebiasis
colon, E. histolytica moves using psuedopodia-like PMNs and macrophages
burrows into wall of gut -- with toxins and enzymes, it forms ulcers
perforation of gut wall & inflammation =
dysentery
amoebas --
go to blood stream -- cause in other places abcesses -- e.g. liver
Cryptosporidium parvum life cycle
Hepatitis
HAV ss+ RNA picorna feco-oral lining of gut, bloodstream, liver
HBV DNA hepadnovirus exchange of blood & body fluids, liver
HCV RNA flavivirus " "
HDV RNA viroid " "
HEV RNA calicivirus feco-oral lining gut to liver
Liver functions
1. Contributes components to digestion [many from gall bladder]
2. remove poisonous byproducts
if liver is not functioning-->nausea, loss of appetite & jaundice
3. clotting factors
if liver is not functioning --> bleed
incidence of different Hepatitis
infections in the US
HAV --
direct liver cell damage by immune response--the virus
is NOT lytic;
mortality 1% -- 5%, infection is NOT chronicif
infected as a child, most have mild illness and then lifelong protectionadult
sero-positivity: 13% Sweden, 88% Taiwan, 97% Yugoslavia, 44% US.virus is resistent
to pH 1, ether, chloroform, detergents, drying, temps to 61•C
HDV -- defective virus,
requires HBV to "help" it--so concurent infection is mandatory. The
HDV uses HBsAg to make a coat for itself-- direct damage to liver cells as exits
HBV & HCV --
immune response mediated damage [three major pathways]
1. If make a strong cytotoxic T cell response: [most common result of HBV &
HCV infection] then acute hepatitis
2. If no immune response: become a chronic asymptomatic carrier
3. If inadequate immune response: chronic inflammation
--> cell death in liver, happens in 5-10% of patients
chronic regeneration: scarring=cirrhosis-->loss of liver function
Dane particles--decoys, more pathology by immune complexes
Additionally for HBV, HCV:
insert DNA into host’s DNA
genetic "hit" 1 step transfromation to being cancerous300,000 cases
of HepB a year in US, 4000 deaths, decreasing since there is now a vaccine
HEV -- direct mortality 1% -- 5%, especially pregnant women
The marine toxins:
saxitoxin: paralytic shellfish poison
made by microalgae [RED TIDE]--after produced enter shellfish. Thgey block Na+ channels and this results in almost instant death once in the blood stream
assay: blend 15-20 clams, boil 5 minute in 0.1 N HCl, adjust pH to 3, inject into mice or rabbits, death if positive--check time until death. detection limit is 40 microgram/100g and the legal limit is twice that much.
tetrodotoxin: Fugu poison --same symptoms as saxitoxin
brevetoxin: neurotoxic shellfish poison
Cigutoxin: Ciguatera fish posion
Domoic Acid: amnesic shellfish poison
