Y1 - Microbio Exam 2 > 10_Enterics I > Flashcards

10_Enterics I Flashcards

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1
Q

microbiome:

define

A
  • all the microbes (microbiota) in and on our bodies
  • includes bacterial, viruses, and eukaryotes
  • microbiota used to be called “normal flora”
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2
Q

where is the microbiome?

A
  • vast numbers of bacteria exposed on the body sites exposed to the environment; and many thousand species of bacteria in the microbiome
  • not usually inside the tissue (blood, deep tissue, sterile)
  • > 100x more genetic material in microbes than human genome
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3
Q

What are the most abundant bacterial phyla in the gut microbiome?

A
  • FIRMICUTES
    • Staph, Strep, Bacillus, Clostridium
  • BACTERIODETES
    • Bacteroides, Prevotella, Porphyromonas
  • ACTINOBACTERIA
    • Mycobacterium, corynebacterium
  • PROTEOBACTERIA
    • Escherichia, and other gram negative enteric organisms
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4
Q

How do gut microbiomes of humans vary?

A

Humans look similar at the phylum level, but

*EACH INDIVIDUAL VARIES AT THE SPECIES LEVEL

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5
Q

Protective functions of:

Gut Microbiome

A
  1. Pathogen displacement
  2. Nutrient competition
  3. Receptor competition
  4. Production of anti-microbial factors, e.g. bacteriocins, lactic acids
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6
Q

Structural functions of:

gut microbiome

A
  1. barrier fortification
  2. induction of IgA
  3. apical tightening of tight junctions
  4. immune system development
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7
Q

Metabolic functions:

of gut microbiome

A
  • control IEC differentiation and proliferation
  • metabolize dietary carcinogens
  • synthesize vitamins (e.g. biotin, folate)
  • ferment non-digestible dietary residure and endogenous epithelial-derived mucus
  • ion absorption
  • salvage of energy
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8
Q

which characteristics of the microbiota in the gut vary amongst individuals?

A
  1. antibiotic therapy
  2. birth method - c-section vs. vaginal birth
  3. diet - vegetarian versus a non-vegetarian
  4. disease states
  5. geographical location
  6. age
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9
Q

how does the microbiota harm us?

A

due to breakdown in the balance betweem microbiota and host immune system

  1. overgrowth of pathogens (e.g. UTI, flesh-eating disease, septic shock)
  2. Inflammatory bowel disease
  3. obesity
  4. type I diabetes
  5. GI cancers - H. pylori
  6. Oral diseases - cavities and gingivitis
  7. Allergy-like (atopic) diseases
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10
Q

Process of inflammation in the Gut Mucosa

A

PAMPS activate the Pathogen recognition receptors –> leads to production of proinflammatory cytokines

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11
Q

**Organism, disease, and mechanism:

  1. shigella species
  2. non-typhoidal salmonella ssp
  3. Yersinia enterocolitica
  4. Campylobacter jejuni
  5. Escherichia coli
  6. Vibrio cholerae
  7. Vibrio vulnificus
  8. Salmonella typhi
  9. Helicobacter pylori
A
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12
Q

define a pathogen:

(4 key characteristics)

A
  1. EVADES/ OVERCOMES defense mechanisms
  2. Finds niche to multiply
  3. Causes disease
  4. Ensures transmission to susceptible host
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13
Q

Diagnosis of diarrheal diseases:

If symptoms include:

  1. Rapid onset (1-16 hours), &
  2. Short duration (<1 day)
A

Think: food intoxication

E.g. Staphylococcus aureus, Bacillus cereus, Clostridium perfringens

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14
Q

Diagnosis of diarrheal diseases:

If symptoms include:

  1. Slower onset, &
  2. Longer duration (>1 day)
A

Think: INFECTION

  • If duration is < 10 days –> likely viruses or bacteria
  • If duration is > 10 days –> likely parasites or HIV
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15
Q

Diagnosis of diarrheal diseases:

If symptoms include:

  1. No fever, or low grade fever
  2. No white blood cells in stool sample
A

Think: SECRETORY DIARRHEA

Consider: Viruses (e.g. rotavirus), or bacteria such as Enterotoxigenic E. Coli, Enteropathogenic E. Coli, Enterohemorrhagic E. coli, or vibrio cholerae.

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16
Q

Diagnosis of diarrheal diseases:

If symptoms include:

  1. fever, &
    1. white blood cells in the stool sample (neutrophils)
A

Think: INFLAMMATORY DIARRHEA

Consider: Campylobacter, Salmonella, Shigella, or EIEC (Enteroinvasive E. coli).

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17
Q

Vibrio cholerae:

causes, transmission, symptoms, conditions for growth

A
  • caused by virulence factors (cholera toxin)
  • transmission:
    • ONLY affects humans
    • human – human transmission (Fecal-oral route), usually thru contaminated water or possibly by food
  • symptoms: rice water stools, aka secretory diarrhea (no WBC or blood in stool)
  • the bacteria grows in salt and fresh water

Epidemiology: 101,000 cases annually –> 2,345 deaths. Only 54 annual cases in US, 0 deaths

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18
Q

What is characteristic of the secretory diarrhea caused by Cholera?

(and amplification)

A
  • Cholera is dease of fluid loss in the GI tract
    • Can result from as little as 25 ug of toxin
  • Rice water stool, w/ 10-20L (or 17-20L) excreted by a cholera patient
    • Filled w/ 105 - 108 bacteria/mL
    • Appearance is due to lots of mucus and bacteria in the stool –> causing it to look turbid.
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19
Q

Important names of scientists working on Cholera, just in case

Study These Flashcards
A
  • Dr. John Snow mapped the cases of cholera in London to find the cause – which was a street pump
  • Robert Koch identified V. cholera bacteria as the cause of cholera outbreaks (comma bacillus) in the stools of cholera patients)
  • Von Pettenkofer and Emmerich were two researchers who challenged Dr. Koch –> determined that some individuals carry genetic mutation which is resistant to cholera
20
Q

Draw the hierarchy/branching of Vibrios

21
Q

process of the cholera toxin infecting a cell

Study These Flashcards
A
  1. cholera toxin binds to intestinal epitheium (enterocytes), enters cell
  2. A subunit permanently ribosylates the Gs alpha subunit of heterotrimeric G protein –>
  3. constitutive cAMP production
  4. high cAMP –> activates (CFTR) cystic fibrosis transmembrane regulator
  5. results in efflux of ions and water from the infected enterocytes
  6. causing secretory diarrhea
22
Q

what is the benefit to the pathogen?

Study These Flashcards
A

You only have to consume a certain amount of bacteria to get sick –>

the number of bacteria amplify in the body –>

excrete into the environment

23
Q

what is the structure of the Vibrio cholerae?

Study These Flashcards
A
  • gram negative, comma shaped bacterium
  • Tcp pili (toxin co-regulated pilus) bundle located at one pole
  • has a single flagellum extending from the same space
24
Q

cholera:

diagnosis and treatment

Study These Flashcards
A
  • diagnosis by dark-field microscopy
    • first, isolate organism on TCBS agar (Thiosulfate-citrate-bile-sucrose)
    • second, test serotype using antiserum to agglutinate organisms
  • treatment:
    • fluid replacement w/ oral rehydration salts or intravenous fluids
    • antibiotics is recommended for severely ill patients (e.g. doxycycline for first line tx for adults, azithromycin for children & pregnant women)
25
Cholera vaccines: what is available?
* **whole killed vibrios given orally plus B subunit of cholera toxin** (not available in the US) * oral vaccines provide protection in 52% of cases the 1st year following vaccination, and in * 62% of cases the second year
26
name the 2 non-cholera vibrios. how do they differ?
1. V. **parahemolyticus** * causes shellfish poisoning * Hemolysin causes Kanagawa phenomenon 2. **V. vulnificus** * fatal bacteremias * opportunistic pathogen in patients w/ underlying liver disease
27
**Kanagawa** phenomenon: define
Production of beta-hemolysis on a special high-salt mannitol medium (Wagatsuma agar) by most strains of Vibrio parahaemolyticus, which produces a heat-stable hemolysin.
28
quorum sensing was first discovered with which bacteria? how?
* with marine bacteria **"Vibrio fischeri"** * isolated from light-producing organ of the squid * V. fischeri can produce light only when large #s of bacteria were present * Each V. fischeri can produce a very small amount of chemical molecular called **autoinducer**
29
Enterotoxigenic E. Coli: transmission, symptoms, consequences
* human to human transmission * sxs: * most common cause of **traveler's diarrhea** * **typical secretory diarrhea** (no WBC or blood in stool) * causes infant mortality in developing countries
30
what are the 3 types of fimbriae (= Pili) of the bacteria causing secretory diarrhea? what bacteria is associated with each?
1. **Conjugative** * e.g. E. coli, F. pili 2. **Type IV fimbriae** * e.g. Toxin co-regulated pilus of V. cholerae 3. **Chaperone/ Usher** * e.g. colonization factors of Enterotoxigenic E. coli
31
what are the assembly/ structural proteins of the ## Footnote **CHAPERONE/ USHER FIMBRIAE?**
Chaperone "CUTS" off romance * **chaperone** (200-250 aa); * located in periplasm * sequesters subunits/ adhesin * **usher** (~800-900aa) * located in outer membrane * sequesters subunits/ adhesins * **tip adhesion** (~300-400aa) * single copy at distal end of filament * N-terminus = binding specificity * **subunits (major and minor) - (**~150-200 aa) * major: main filament * minor: tip fibrillum
32
what are the **surface appendages** of the chaperone/usher fimbriae?
1. **THICK (6-8nm) - rigid fimbriae w/ tip fibrillum** * \> 3 subunits per turn * e.g. E. coli CFA/ fimbriae from ETEC, or E. coli P fimbriae 2. THIN (2 nm) - flexible fibrillar structures * 2 subunits per turn * e.g. F18 fimbriae from ETEC
33
what is the purpose of the chaperone/ usher fimbriae?
allows the bacteria to bind to carbohydrate receptors on epithelial cells --\> results in disease (if the fimbriae is destroyed or ineffective, then the bacteria can't cause disease)
34
epidemiology of chaperone/ usher fimbriae points to a role as host range factors
For example, in the **human isolates of Enterotoxigenic E. coli (ETEC)** have the following chaperone/ usher fimbriae: * CFA/I, CS1, CS2, CS3, CS4, CS5, CS6
35
E. coli and respective symptoms. Which are pathogenic? Commensal? Symptoms caused?
36
where are the TYPE III secretion system needle structure encoded?
* encoded on pathogenicity islands of pathogenic: * E. coli * Shigella * Yersinia * Salmonella * Pseudomonas
37
Enteropathogenic E. coli (EPEC): transmission, symptoms, mortality
* human to human transmission by virulence factors/ mechanisms * symptoms: * weanling diarrhea significantly contributes to infant mortality (developing countries) * typical **secretory diarrhea** (no WBC or blood in stool)
38
which bacteria has the **LEE pathogenicity island**? and what is it?
* **LEE pathogenicity island**: locus of enterocyte effacement --\> encodes the proteins responsible for attaching and effacing (AE) lesions in the large intestine * These are found on the EPEC (enteropathogenic E. coli)
39
EHEC (Enterohemorrhagic E. coli) transmission, sxs
* transmission: * animal to human (zoonosis) * raw or undercooked ground meat products, raw milk and faecal contamination of vegetables * sxs: * Shiga toxin can cause blood in stool * Shiga toxin can cause hemolytic uremic syndrome
40
how is E. coli O157:H7 differentiated?
differentiated by its inability to ferment sorbitol
41
which types of E. coli have the LEE genetic region? what about STX phage?
* LEE gene --\> found in Enteropathogenic and Enterohemorrhagic E/ coli (EPEC, and EHEC) * STX phage --\> is found in the Enterohemorrhagic E. coli (just EHEC)
42
**Shiga-like toxin:** found in which E. coli? encoded by what? function?
1. found in Enterohemorrhagic E. coli 2. encoded by STX phage 3. Function: * bacteria remain localized in the intestinal lumen * upon bacterial lysis, the toxin is released and enters the blood stream * --\> * damage to the microvasculature --\> * blood in stool and/or * hemolytic uremic syndrome (HUS)
43
hemolytic uremic syndrome (HUS): define
a group of blood disorders characterized by low red blood cells, acute kidney failure, and low platelets sxs include: bloody diarrhea, fever, vomiting, and weakness
44
what do the following pathogens have in common? ETEC, EPEC, EHEC, and V. cholerae
* Non-invasive * Colonization factors * Toxin production * Lead to secretory diarrhea
45
What type of agar is used for detection of enteric bacterial species?
Sorbitol MacConkey agar: Lactose + --\> E. coli, enterobacter, klebsiella Lactose - --\> Salmonella, Shigella, Proteus
46
List 3 Lactose Positive bacteria (by MacConkey agar), List 3 Lactose Negative bacteria
Positive: 1. E. coli 2. Enterobacter 3. Klebsiella Negative 1. Salmonella 2. Shigella 3. Proteus
47
What is the EMB agar?
Eosin methylin blue media; designed to discourage the growth of gram positive bacteria
Y1 - Microbio Exam 2
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