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Micro Chapter 2


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How are flagella affixed to bacteria?

Name a bacteria that has a single polar flagella.

Name a bacteria that have peritrichous flagella.

Name a bacteria that has no flagella.
By BASAL BODIES spanning entire cell wall.

1. Vibrio cholera: 1

2. E.coli: lots

3. Shigella: none
What straight filaments arise from the bacterial cell wall and make the bacterium look like a porcupine?

What are they called when they serve as adherence factors?
1. Pili

2. adhesins
e.g., Neisseria gonorrhea has pili that allow it to bind to cervical/buccal cells to cause gonorrhea.
How do the following bacteria utilize pili?

1. Neisseria gonorrhea
2. E. coli, Campylobacter jejuni
3. Bordetella pertussis
1. pili allow it to bind to cervical cells to cause gonorrhea
2. pili/adhesins bind to intestinal epithelium--without pili can't cause diarrhea
3. uses adhesins to bind to ciliated respiratory cells and cause whooping cough.
What is unique about the capsule of BACILLUS ANTHRACIS?
Bacillus anthracis is unique in that its capsule is made up of amino acid residues (instead of simple sugar residues)
How do capsules enable bacteria to be more virulent?

Which strep strains cause rapid death, (S) or (R)?
Capsules prevent phagocytosis by macrophages and neutrophils.

S strep is smooth because it is encapsulated. R strep is rough because it is unencapsulated and therefore less virulant.
What two important tests enable doctors to visualize capsules under the microscope?
1. India Ink Stain (capsule is transparent halo around cell--used to ID fungus CRYPTOCOCCUS)

2. Quellung reaction: bacteria mixed with antibodies that bind to capsule, causing capsule to visibly swell.
What two genera of bacteria form endospores?
Aerobic gram (+) BACILLUS
Anaerobic gram (+) CLOSTRIDIUM
What is an exosporium?
the outermost layer of an endospore.
Name the 7 facultative intracellular organisms that can survive after phagocytosis. How do they survive?

1. Listeria monocytogenes
2. Yersinia
3. Salmonella typhi
4. Francisella tularensis
5. Mycobacterium
6. Brucella
7. Legionella

They survive by inhibiting phagosome-lysosome fusion, thus escaping oxygen radicals.
What classes of bacteria release exotoxins?
All major gram-positive genera except for Listeria (endotoxin)

Gram negative bacteria like cholera and e. coli
Name four severe diseases caused by bacterial exotoxins:
botulism, tetanus (neurotoxins)
cholera (enterotoxin)
What two disease manifestations result from enterotoxins. How do they work?
1. INFECTIOUS diarrhea: bacteria colonize and bind to GI tract, releasing endoterotoxin locally. (cholera, e. coli, campylobacter jejuni, shigella)

2. FOOD POISONING: bacteria release enterotoxin into food, which causes 24 hour diarrhea/vomiting when ingested. (bacillus cereus, staph aureus)
What symptoms do PYOGENIC EXOTOXINS cause?

Give two examples of pyogenic bacteria.
Rash, fever, toxic shock syndrome -- through release of cytokines.

Staph aureus and Strep pyogenes
What characteristic is shared by the exotoxins of Bacillus anthracis, Clostridium botulinum, Clostridium tetani, Corynebacterium diphtheriae, and Vibrio cholerae?
Their exotoxins are all composed of TWO polypeptide subunits bound together by disulfide bridges:

1. (B)inding/(H)olding subunit binds to target cell
2. (A)ction/(L)aser subunit enters cell and exerts the toxic effect.
Why does treating a patient who has a gram (-) infections with antibiotics sometimes worsen the patient's condition?
Because when the bacteria get lysed they release large quantities of ENDOTOXIN (lipid A, a piece of the outer membrane LPS) which is very toxic and released when cells undergo lysis.
What is sepsis?

What are some symptoms of sepsis?
Bacteremia that causes a systemic immune response to the infection.

High/low temp, high WBC, fast heart rate, fast resp rate: "looking sick"
What is the chain of events that lead to septic shock?
1. Localized site of infection of bacteria or fungi.
2. organisms release endotoxin or exotoxin that circulate in bloodstream and stimulate macrophages/PMNs in immune response.
3. These cells release TNF (cachectin) and other endogenouse mediators of sepsis.
4. TNF triggers release of cytokine IL-1 from macrophages and endothelial cells, triggering release of other cytokines/prostaglandins.
This ultrimately turns against the body.
Why is tumor necrosis factor (TNF) also called CACHECTIN?
because it is released from tumors, producing a wasting syndrome called cachexia.
What are the effects of septic shock on the vascular system?
Vasodilation, causing HYPOTENSION and organ HYPOPERFUSION
What are the effects of septic shock on the heart?
Myocardial depression, causing
1. decreased cardiac output
2. decreased blood pressure
3. organ hypoperfusion
What are the effects of septic shock on the kidneys?
Acute renal failure, causing
1. decreased urine output
2. volume overload
3. accumulation of toxins
What is the effect of septic shock on the lungs? the brain?
Adult respiratory distress syndrome, causing HYPOXIA

Encephalopathy, causing alteration in mental status
What are the effects of septic shock on the liver?
Hepatic failure, causing accumulation of metabolic toxins and hepatic encephalopathy
What is the effect of septic shock on the coagulation system?
DIC: disseminated intravascular coagulation
causing clotting and bleeding
What is the most important principle of septic shock treatment?? Where is the most common place to look?
Find the site of infection and the bug responsible and eradicate it!! Start EMPIRIC THERAPY with broad coverage antibiotics, support bp with fluids and drugs (norepi, dopa), maintain oxygenation.

Lung is most common site (pneumonia) followed by abdomen and urinary tract.

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