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Enterobacteriaceae I, II, III (Hull)


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Disease caused by the enterobacteriacea are divided into two groups:
1) GI tract diseases
2) extra-intestinal disease
Fact: Normal habitat of the enterobacteriacea is in the intestines of all mammals, reptiles, insects too!
Fact: Enterobacteriacea are the most common cause of UTIs (both community & hospital acquired...E. Coli is #1)
Gram - bacteria (chain/do not chain)
Use selective and differential media to grow the enterobacteriacea on, name two of them and describe...
1) MacConkey's agar - has lactose on it with the pH indicator being it turns red for something that ferments lactose
2) EMB - has lactose and its pH indicator turns a green metallic sheet when the organism ferments lactose
What is meant by selective media?
Used to inhibit the growth of other organisms so others can grow (ie MacConkey's is selective for the growth of gram negatives, and suppresses the growth of gram +)
Name the three enterobacteriacea that are lac+
1) E. Coli
2) Klebsiella
3) Enterobacter
What are the four genera that cause GI tract disease?
1) E. Coli - only a few strains (different than those that cause UTIs). Causes diarrhea
2) Shigella - four species of this (flexneri, dysenteriae, and 2 others...just know that dysenteriae is the most severe yet it doesn't occur in the US). Causes dysentery
3) Salmonella - all the serovars were classified together as S. enterica, but then still refer to S. typhi serovar separate from the rest because it causes typhoid fever). S. enterica cause gastroenteritis (vomiting and diarrhea), whereas S. typhi causes typhoid fever
4) Yersinia enterocolitica causes enterocolitis.
The gram negative equivelant to the catalase test of the gram positives is ________
Enterobacteriacea are oxidase (positive/negative) whereas the rest of the gram negatives oxidase (positive/negative)
negative, positive
Flagella are very antigenic and antibodies made against them are protective, so why do we not consider them that important in regards to occurrence and recurrence of disease?
Because unfortunately lots of types of flagella they can make, so you can keep getting reinfected anyways
Flagella are responsible for _________ on culture plates. And which enterobacteriacea does this best?
swarming (make successive waves as each progressive), proteus
capsule is considered the ____ antigen. Flagella is the ___ antigen.
K, H
True or false - both gram negatives and gram positives can have capsules?
TRUE! But all bacteria don't need capsules to survive, but having one usually helps for anti-phagocytic purposes (therefore helps for the pathogenic kinds)
Organelles of attachment are the ________
fimbrae (pilli)
What does the helical lipoprotein on the inner face of the outer membrane do?
anchors to the thin peptidoglycan layer in the periplasmic space to hold down the OM and keep it from floating away
Since gram negatives are actually susceptible to complement forming its MAC and putting holes in it since its cell wall is so THIN, how do the gram negatives get around this?
1) have capsules which are antiphagocytic as we know (prevent complement and antibody interactions, contrasts to what musher said in lecture 1 though!)
2) The O antigen allows for complement to bind to it, thus detracting the complement away from where it would really do damage (at the membrane) and to an area where it won't do anything really
As gram negatives spread in the blood they give off membrane blebs containing ________, that are bound in the bloodstream by ______ which are then recognized by _____ on macrophages which then ilicits the production of ______ and _____ and other cytokine
endotoxin (lipid A and all of the LPS), bound by LBP in the blood, recognized by CD14 on the macrophages, ilicits production of TNFalpha and ILs (1, 6, 8 etc)
Common cause of death in elderly people because of gram negative infection is...
gram negative sepsis that can ensue
Compare endotoxins and exotoxins
*made only by gram negatives
*poor antigens
*weak toxic effects
*very pyrogenic (cause fever)
*are LPS (lipid, and polysacc)

*made by both gram + & -
*highly antigenic (remember diphtheria and tetanus toxins so great they are put in other vaccines to make them better!)
*highly toxic effects (botulinum and tetanus toxin are by far the most powerful biological toxins in the world)
*poorly pyrogenic (don't cause fever except for the Strep A pyrogenic exotoxins we discussed)
*are protein (thus explaining their heat lability)
Enterobacteriacea are responsible for many __________ (institutional as well) acquired infections
What is the #1 nosocomial infection?
UTI (because of indwelling or foley catheter)
E. Coli is responsible for 90% of community acquired UTIs, but this number drops drastically in the hospital setting to 40%. What other 3 groups rise?
1) Candida
2) gram positives (Staph. saprophyticus, enterococcus)
3) less virulent gram negatives
True or false - in hospital acquired infections it is very common to find more than 1 microbe (2 or 3 in an infection) whereas a community acquired is usually caused by 1 type of bacteria.
Control of enterobacteriacea is largely through what means?
public health measures, personal hygiene
There are NO vaccines for the enterobacteriacea except for ________.
typhoid (S. typhi)
Intraabdominal abcesses are caused by ______ or _____
trauma, surgery
Penetration of abdominal cavity may introduce bacteria (perforating the intestine) which can cause an abcess or a peritonitis. These infections that result are usually gram +/gram-/mix
How do you treat these abcesses?
1) Antibiotics (but not alone because the abcess isn't getting perfused good enough)
2) Surgical removal and drainage of the abcess. MUST BE DRAINED SURGICALLY!
Name the five strians of E. Coli that we are concerned with?
EHEC (hemorrhagic), ETEC (toxigenic), EAEC (adherent), EIEC (invasive), EPEC (pathogenic)
FACT: Remember that the E. Coli that cause the GI Tract disease are very different than the types that cause the extra intestinal disease (ie UTIs). They have different genes that cover different properties that allow for a UTI or for a diarrhea.
FACT: People who are heroin/crack addicts are more susceptible to getting these pathogens (the GI Tract diarrhea) because these drugs SLOW DOWN THEIR MOTILITY through the GI system, allowing pathogens to hang out longer.
FACT: It is difficult for a clinical lab to distinguish among these pathogenic and normal E. Coli in the flora because they look alike (have same morphological features) so they have to resort to more specific testing we didn't talk about.
FACT: endemic means that someone in the community always has something, epidemic means breakout. pandemic is a worldwide epidemic
ETEC is the #1 cause of what two things?
1) traveler's diarrhea
2) death in children in developing countries
What is your answer to the question "Well why aren't the adults in these countries getting ETEC too?"
Well, they are technically. They got them as kids, and those that survived had protective antibodies (IgA) that they secrete everytime they drink their own water. Therefore, their incidence decreases over time for this very reason in addition to the fact they are constantly inocculating their immune system with more of the pathogen (essentially boosting themselves everytime they drink the water). Remember the curve shifted to the left headed down as individual grows older.
Are ETEC invasive?
NO, remain out sitting on the epithelial surface pumping out their toxin
ETEC makes one or two or both of toxins, name them and describe their mode of action.
1) Heat stabile enterotoxin - don't be confused, yes it is an exotoxin and yes exotoxin's are supposed to be heat labile, but this one is an EXCEPTION because it is so small it is heat stabile. This toxin binds to guanyl cyclase, increases cGMP production, which increases phosphorylase activity, which leads to ion loss from cell followed by water loss contributing to watery diarrhea.
2) Heat labile enterotoxin - VERY similar to the A-B toxin of cholera (remember TC...Taco Cabana). This binds to adenylate cyclase, increases cAMP production, again causes ion and water efflux leading to a watery diarrhea
Name three things that cause a bloody diarrhea
Shigella, bacillus anthracis, EHEC
What does EPEC do?
Not much is known about it except it attaches to the cell and pumps in proteins that cause a rearrangement of the epithelial cells cytoskeleton. Rearranges actin filaments.
EHEC is/is not of origin and common in the US versus the other types of E. Coli that cause diarrhea.
The hallmark of EHEC is its bloody diarrhea, explain how its toxin causes this
EHEC's enterotoxin is VERY similar to Shigella, and therefore called SLT-1 and SLT-2 (shigella like toxin). It goes into the cell and deadenylates the ribosome, halting protein synthesis, and thus killing the cell!
FACT: Can't eat a rare hamburger, but you can eat a rare steak (steak muscle is too thick for E coli to go through so just have to make sure the outside is cooked enough). But hamburger meat is like a bunch of cows put into a blender and all sorts of par
FACT: hamburger meat isn't the only shit that can have EHEC in it (remember apple juice, some smoked meats too that are uncooked like salamni)
Explain what hemolytic uremic syndrome is?
When have EHEC that makes tons of toxin that disseminates into the bloodstream will lyse red blood cells so now you have a bloody diarrhea and bloody urine. Can cause kidney failure and death in the person.
What specific type of E. Coli causes the presentation of EHEC?
O157 H7
What is the most common cause of OUTBREAKS of diarrhea?
S. enterica causes gastroenteritis. What does this mean?
Means that there are vomiting as well as diarrhea problems.
Is Salmonella invasive?
Yes, it crosses the epithelial border into the lamina propria where S. enterica is ingested and normally taken up by the M cells here. However, S. typhi bypasses all of this and disseminates further into the bloodstream.
FACT: Can pass salmonella transovarialy they have found. So, just because an egg isn't broken doesn't mean you can eat it raw anymore
FACT: Salmonella is not very serious in terms of mortality (remember the outbreaks in chicago, 175,000 got it but only 2 died)
What else carries Salmonella besides chickens?
reptiles! turtles (remember the story about Sam and Ella from the osteomyelitis lecture).
The only way to get diarrhea is if....
So, if you have disease (vomitting) within hours of eating something its most likely...
bacillus cereus (from preformed emetic toxin) or staphylococcus aureus (from its preformed enterotoxin).
Salmonella typhi is a different story. Explain its pathogenesis.
S. typhi is not killed in the Peyer's patches of the intestine like other salmonella usually is. It dessiminates into the bloodstream where every organ can become infected (ie lungs, especially gallbladder).
S. typhi are very resistant to _____ explaining why they can live in the _______-
bile salts, in the gallbladder... remember the two properties of gram negative bacteria that confer resistance to hydrophobic antibiotics, bile, and disinfectants (the MDR efflux pumps, and the fact that their outer membrane is so tightly packed with LPS it decreases permeability)
FACT: The S. typhi in the bloodstream can lead to septic shock, fever, and multiple organ failure for all the reasons you already know about Lipid A
FACT: diarrhea is not really common in typhoid fever. Sometimes may cause cramping.
Survivors of typhoid fever may become lifelong carriers. Explain how they may reinfect themselves or constantly secrete out some in their feces.
The S. typhi has a predelection for staying in the gallbladder (attaches to gallstones over time) and the person will secrete low numbers of bacteria into their stool for years. Person may appear fine because you don't get typhoid fever again once you've had it (have protective antibodies). Remember the story about Typhoid Mary.
FACT: can get ulceration of the intestine from typhoid fever which can allow other flora to get into the abdomen and cause peritonitis
FACT: You treat typhoid fever infection with 1) bacteriocidal antibiotics, 2) antibiotics that can cross the eukaryotic cell membrane because these are facultative intracellular pathogens
How do you diagnose typhoid fever?
Want to check sterile locations, so you isolate samples from the bone marrow and blood to test for its presence.
Shigella causes _______
FACT: Shigella likes to break out during wars, famine
FACT: Shigella is extremely virulent, takes only 10 bacteria to cause disease
Shigella is very common in daycare centers because of what two things?
1) Babies diapers, so kids can give it to eachother because they touch everything to their mouths
2) from workers at the daycare center changing diapers
Unlike salmonella, explain the pathology of shigella
They like to just sit in the epithelial cell instead of crossing through it. So, they sit there and release their shiga toxin which removes 28S RNA of the eukaryotic ribosome, stopping protein synthesis and killing the cell. All the way, shigella is going through a cycle of penetration, growth, and release upon cell death (this leads to massive ulceration in the intestine as well).
When diagnosing for shigella what do you do?
LOOK AT THE STOOL DIRECTLY, because white blood cells get into the stool and this is unique to see.
What can you get from raw oysters?
S. typhii apparently?, Hepatitus A, Shigella, V. Cholera!
What infection is commonly mistaken for appendicitis?
Yersinia enterocolitica
Yersinia enterocolitica's toxin is heat ______ and is very similar to what?
heat stabile, similar to the heat stabile enterotoxin of ETEC
Where are the reservoirs of Yersinia enterocolitica?
domestic animals, wild animals (for backpacking trips), cold mountain streams way up in the moutains, can grow at 4 degrees celsius!
Which of these pathogens is found more commonly in temperate climates (not tropical). Example given was its the most common cause of diarrhea in Toronto children.
Yersinia enterocolitica
Bubonic and pneumonic plague are caused by what?
Yersinia pestis
Where is the most likely site of bubos (swollen lymph node) from bubonic plague and why?
groin area, because fleas can only jump so high
FACT: Those with the plague die of gram negative sepsis and shock
FACT: pneumonic plague is worse than bubonic plague because of the route of transmission (just through aerosol particles from coughing!)
Why is the plague called the black death?
Because of the ensuing ischemia and necrosis of distal appendages (nose, lips, hands all turn black)
Where in the US is yersinia pestis still common and in what reservoir?
In the western US it is still common to see warning signs for this "Don't feed the rodents." Because some of the rats escaped into the wild when got off trade ships from china and bit rodents.

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