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
Saliva
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 protection adult 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