Download Microbiology bio 123

Module C-12
Oral and Digestive Pathogens
Oral cavity:
Purpose: Intake and chewing of food
Structure:
Soft surfaces – tongue, cheeks, and gingiva. These surfaces are renewable.
Hard surfaces – bony sockets where the teeth fit in, and the enamel of the teeth. These are not renewable.
Periodontal membrane – holds that tooth in place (ligament) made mostly of collagen
Root contains cells, blood vessels, etc.
Gingival crevice (sulcus) – the place where the enamel and gingiva meet.
Normal Flora:
Gram positive streptococci; most are alpha-hemolytic.
 Streptococcus viridians (Gram positive cocci; alpha hemolytic) makes up majority
 Streptococcus mutans (facultative anaerobe)
 Lactobacillus acidophilus
 Can have about anything because mouth is very hospitable for bacteria. Tongue has lots of crevices.
There are 100 bacterial cells for every 1 tongue cell.
Tooth decay and gum disease:
Endogenous – comes from host’s own flora
Progression – conditions change over time. As they change the disease gets worse unless something stops it. As
organisms overgrow they change the environment and make it suitable for other types of organisms. Process
keeps going unless it is stopped. Gum disease and tooth decay are preventable.
Teeth have an “acquired pellicle” – a thin film of protein that comes from saliva and sticks to teeth. Has slightly
negative charge (opposite of bacteria’s positive charge). Attracts bacteria.
Sulcus is crevice, so debris will gather there. This accumulates; bacteria and debris forms plaque against the
tooth. This leads to gingivitis (inflammation of the gums).
ANUG = Acute Necrotizing Ulcerative Gingivitis – “Trench mouth.” Results from poor oral hygiene and
chronic stress. When two types of normal flora combine and cause disease. Common in soldiers and AIDS
patients. No real treatment aside from extraction.
All dental problems began with introduction of refined sugars.
Pathogens
1. Streptococcus mutans
1. Is a facultative anaerobe
2. Ferments that sugar in the debris and produces a lot of acid
3. Produces enzyme isomerases which can convert dextrose to dextran and levullose to levan (these
isomer sugars are very sticky and cause the molecules to bind to the teeth)
4. Tooth decay tends to occur around 5 on the pH scale
5. We believe that the bacteria are typically biofilm associated
6. Is considered to be the most common cause of tooth decay
7. Because of the production of acid, the S. mutant changes the pH of the sulcus, making it unable to
survive
8. Because of the change in pH, Lactobacillus acidophilus will then colonize the sulcus
2. Lactobacillus acidophilus
1. Important member of normal flora in the mouth, digestive tract, and vagina
2. Possibly the most important factor in controlling yeast infections
3. important in keeping digestion working normally
3. Actinomycetes naeslundii
1. Is an obligate anaerobe
2. Lives deep in the sulcus
3. Takes the calcium salts out of your saliva and mineralizes them, this forms calculus
4. Calculus feels like concrete with glass embedded in it
5. If you do not remove the calculus, you will start to get periodontitis
4. Bacteriodes melonogenicus
1. Produces proteolytic enzymes (breaks apart proteins)
2. Causes the breakdown of the periodontal membrane (ligament) which causes loose teeth. Produces a
toxin that is chemotactic factor – attracts osteoclasts that break down bone. Still normal flora because
it is endogenous.
Tooth decay progression
1. Plaque
2. Stagnation
3. Calculus
4. Critical pH of 5, starts tooth decay
Soft tissue disease progression
1. Gingivitis (soft tissue swelling)
2. If untreated, will progress to periodontitis (when the gums begin to pull away from the teeth)
Saliva rinses the hard and soft tissue and buffers against acid that is created by the bacteria.
Plaque – the accumulation of debris and bacteria that goes into the sulcus.
Bacteria that are in this sulcus are typically anaerobes and produce acid due to fermentation of the debris.
Biofilm – a group of organisms that live together on one surface. The bacteria attach themselves to the surface.
These bacteria tend to be more resistant to antibiotics.
Endogenous process – when the disease comes from the normal flora of the host itself, therefore it is not
communicable.
Tooth decay is an endogenous process.
Pellicle – The salivary proteins are attracted to the enamel of the teeth forming the pellicle.
Digestive tract:
Normal Flora:
Stomach – none due to acidic pH. To consume food that makes us ill we have to consume large amounts of
microorganism so that some make it to intestinal tract, unless it is an acid-tolerant microorganism.
Upper small intestine – 10x3 bac/milliliter (aerobes and facultative anaerobes)
Lower small intestine – 10x5 bac/milliliter (aerobes and facultative anaerobes)
Colon – 10x11 bac/milliliter (mostly anaerobes. Feces is more than 50% bacteria)
Small intestine:
1. Lactobacilli (most important for maintenance)
2. Streptococci
3. Yeasts (albicans, etc.)
Stomach
Pathogens
1. Helibacter pylori
a. Transmitted by fecal/oral route
b. Burrows under the mucus lining of the stomach and can burrow into the stomach lining.
Causes most stomach ulcers.
I.
Diseases caused by enteric organisms (those that live in intestine and affect lining):
A. Those that cause gastrointestinal upset (cramps, nausea, vomiting, and diarrhea):
I.
Bacteria that gain access to the intestine, multiply there, and produce enterotoxin (toxin that
works on the intestinal tract). Caused by enteric organisms (effect intestinal tract)
1. Vibrio cholera
a. Attaches to the intestinal wall and produce a toxin called choleragen
b. This toxin inhibits the intestinal wall from absorbing sodium ions. Water follows sodium,
therefore causing diarrhea, electrolyte imbalance, and dehydration
c. The stool has been described as “rice water” stool due to water and shredded intestinal
tissue. People can lose up to 25% of their body weight in a day (20 L)
d. Still endemic to some parts of the world due to contaminated water
e. Organism is lysogenic conversion via virus inserting its DNA into a bacterial cell (virus is
a prophage and bacterial is lysogenic cell)
f. Organism can survive in cold water for quite some time
g. Treatment: IV rehydration and tetracycline
2. Vibrio parahemolyticus
a. Caused from eating raw shell fish
b. Coastal organism
c. Not as severe as Cholera
3. Enterobacteriaceae family – All have the ability to cause GI upset. Some have the ability to
ferment lactose and are classified according to if they can or cannot. Coliforms ferment
lactose and are used as an indicator of fecal contamination. Non-lactose fermenting
microbes tend to be worse.
 Enterotoxin producing E. coli
a. Is a lactose-fermenting coliform
b. Produces enterotoxin (a type of exotoxin)
c. Spread via fecal-oral route by contaminated food/drink
d. Is normal flora; there is a max number allowed in food and past that is considered
contamination. Some are worse than others.
e. Can cause dysentery - blood or pus in the stool
f. Incubation period - 2 hrs to 6 days
g. Treatment - rehydration; antibiotics (gentamycin) in young children and infants
h. The most severe strain currently is 0157:H7
i. This infection is referred to as Traveler's Diarrhea, Montezuma’s Revenge, etc. (lasts
about 10 days)
 Salmonella
a. Gram negative
b. Causes salmonellosis
c. Spread by contaminated food/water
d. Are NLF (non lactose fermentors),
e. Transmitted through fecal/oral route from animal sources
f. We ingest the living organism – killed by stomach acid so we need large amounts to
make us sick
g. Incubation period from 16-18 hrs
h. Produces an endotoxin
i. Common sources:
1. Turtles
2. Iguanas
3. Chicks and ducks, eggs, poultry in general – normal flora in chickens and we get it
when it spreads to their skin
 Salmonella typhi
a. Causes typhoid fever (typhoid Mary carried this bacteria)
b. Transmitted by fecal/oral route from humans, not typically animals
c. Carried in gall bladder
 Shigella
a. Causes “bacillary dysentery”
b. Non-lactose fermenting
c. Shigellosis
d.
e.
f.
g.
h.
i.
j.
Watery, bloody diarrhea
Headache, stiff neck, convulsions, joint pain
Has human source; poor sanitation
Spread by fecal-oral route
Not killed by stomach acid so we only need a few to make us sick
Creates shiga toxin – very powerful
Treatment – rehydrate patient. Antibiotics do not cure, only shorten duration of
symptoms
2. Campylobacter jejuni
a. Gram negative, vibrio shaped
b. Produces toxin (enterotoxin)
c. Corkscrews under mucus membrane and causes diarrhea
d. Normally found in dairy cattle, chickens, and other types of fowl
e. Has been recognized as a major problem in the last few years and may now be the
most common bacteria in food
3. Clostridium perfringens
a. Common source is foods that are being kept warm for a long period of time
b. Initial cooking does not kill the spores and when the temperature is decreased the
bacteria returns to living state and produces toxins
c. Incubation period 18-24 hrs
d. Biscuits and gravy and the most commonly indicated foods
e. Found in soil, animal feces, meat and poultry contaminated at slaughter
f. Causes gas gangrene in wounds
g. Obligate anaerobe
h. Gram positive
4. Clostridium Difficile
a. Also called “C-diff”
b. Toxins A & B bind to unhealthy tissues
c. Obligate anaerobe, gram positive bacillus, spore former
d. Usually only cause problems when the normal flora, especially the Lactobacilli, have
been disturbed by antibiotics, etc.
e. This causes a pseudomembranous colitis (severe diarrhea, destruction of the lining of
the intestine)
f. Creates watery diarrhea with no blood and plaque-like pseudomembrane
g. The risk to the general public is very low – generally found in hospitals
h. Treated with Flagyl (Metronidazole)
i. Isolate patient to prevent spread
j. Stop antibiotics
k. Use soap and water; antimicrobial rubs doesn’t kill spores
II. Bacteria in intestines - do damage, but do not produce toxins:
1. E. coli
a. They are called enteropathogenic (don’t produce toxins but still do damage)
2. Entamoeba histolytica
a. Protozoan
b. We ingest cysts then they break open and burrow into intestines
c. Organism burrows into the intestinal lining which causes inflammation, This causes fluid to
be retained in the intestine, which causes diarrhea or amoebic dysentery
d. Transmission, unsanitary conditions, fecal/oral route and homosexual men
e. Treatment is with Flagyl
3. Giardia lamblia
a. Protozoan
b. Causes backpackers disease (giardiasis)
c. Causes dysentery
d. Spread by contaminated water and person-to-person contact (daycare centers). People can be
carriers.
e. Incubation period is 6-20 days
f. Can be from really mild to severe and can become chronic
g. Treatment is with Flagyl
4. Viral gastroenteritis
a. Most common form of gastroenteritis
b. Shortest length of symptoms (24-48 hours)
c. Biggest problem is dehydration – rehydrate patient
d. Viral groups involved:
1. Rotavirus
a. Causes “toddler diarrhea”
b. Effects children about the age of 3
2. Norwalk agent
a. Most common in adults
b. Causes about 80% of the viral gastroenteritis incidents – most of the time GI upset is
viral
c. Commonly found on cruise ships
III. Bacteria that produce an exotoxin - causes symptoms - do not reside in the intestines
(bacterial intoxication)
With these microbes, we are consuming ready-made toxin so it works immediately on the GI
tract.
1. Staphylococcus aureus
a. Called “staphylococcal enterotoxicosis”
b. The toxin that is produced causes inflammation in the GI tract which causes the diarrhea and
vomiting
c. Can affect some nervous center reflexes
d. The toxin is heat stable – even if heated it isn’t effected
e. Incubation of 1-7 hrs. (note: short exposure to symptoms means ready-made toxin)
f. Generally short duration (24-48 hrs.)
g. Most commonly found in potato salad. Staph loves starch.
IV. Enter through the oral route - cause problems elsewhere in the body:
Affects other parts of body, not GI tract.
1. Brucella albortus
a. Causes brucellosis
b. Gram negative cocci bacillus
c. Spread by working with infected animals or by consuming their products
d. Typically carried by sheep, cattle, pigs, goats, deer, etc.
e. Symptoms are chills, high fever, and drenching sweats
f. Causes spontaneous abortion in animals, hence its name. Doesn’t have same effect in
humans.
g. Treatment is with tetracycline
Viruses
1. Hepatitis A (HAV)
a. Infectious
b. Fecal/oral route, raw shell fish, and day care centers (person-to-person)
c. Vaccine available
d. Targets the liver, not intestinal tract
e. most obvious symptom is jaundice, but not always present
f. when you have jaundice you are in the icteric phase of the disease
2. Hepatitis B (HBV)
a. Serum hepatitis – spread by blood, semen, mother to fetus. Does not involve GI tract.
3. Polio virus
a. Effects motor neurons (nervous system)
b. Contaminated water
c. Gains entrance through the GI tract
d. Results in a flaccid paralysis, causes loss of motor function but no loss of sensation
4. Adeno viruses
a. Respiratory viruses
b. Transmitted by fecal/oral route
5. Coxsackie viruses
a. Shed in the feces
b. Can cause meningitis
c. Transmitted by fecal/oral route
V. Organisms that produce toxins that are ingested
We ingest ready-made toxin that targets another area of the body.
1. Clostridium botulinum
a. All the bacteria are soil dwelling, in the spore form on the surface of the soil, these spores
will return to the living state and produce a toxin in an anaerobic environment, these
toxins are ingested which cause problems in the body
b. Most potent toxin known
c. Can be fatal
d. If ingested, it is a neurotoxin, and will have neurological effects. It inhibits that release of
acetylcholine from nerve cells.
e. Stomach doesn’t kill toxin
f. All the bacteria are gram positive
g. Most common in green beans
h. Common causes
a. Home canning
1. Boiling
2. Pressure canning – need to use this method to kill spores
i. Produce exotoxins which are heat labile (susceptible to heat)
j. S/S - headache, depression, nervous symptom symptoms (double vision), loss of muscle
control, flaccid paralysis (voluntary then involuntary), ending in respiratory collapse
k. Infant botulinism - if the infant ingests the spores of the botulism, they can colonize the
colon and produce the toxin there, can cause constipation, poor feeding, palsies, failure to
thrive, respiration, and can be fatal, main source is honey
2. Aspergillus flavus
1. Produces aflatoxins, which is a liver carcinogen. These toxins affect the liver and have been
associated with liver cancer
2. Is a fungus
3. Is found in moldy foods such as peanuts and grains, can be in tree nuts
4. Damage can be in different ways
a. Acute
a. Large amounts of toxin at one time
b. Cumulative
a. Ingesting toxins over a long period of time
With enterobacteria, the ability to ferment lactose is very important.
The bacteria that ferment lactose are referred to as coliforms, and are used as indicators of fecal contamination.