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Hardcore Microbiology > 30 Eneterobacteriaceae > Flashcards

30 Eneterobacteriaceae Flashcards

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1
Q

Is Eneterobacteriaceae motile? What type of G and form in microscope? Spore forming? Ferment glucose? Catalasa positive? Reduces nitrate? Oxidase positive?

A
  • Most, G (-) rods, no, si, si, si, no.
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2
Q

Which strains of enterobacteriaceae ferment lactose? (5)

A
  • Escherichia, Klebsiella, Enterobacter, Citrobacter, Serratia spp.
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3
Q

Which strains of eneterobacteriacea do not ferment lactose or do so slowly? (4)

A
  • Proteus, Salmonella, Shigella, Yersinia spp.
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4
Q

Which strains of enterobacteriacea are resistant to bile salts? (2)

A
  • Shigella, Salmonella
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5
Q

Which strains of enterobacteriacea have prominent capsule? (3)

A
  • Most Klebsiella, some Escherichia and Enterobacter strains.
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6
Q

What are the 3 major groups of antigens found in Enterobacteriaceae?

A
  • Somatic O polysaccharides, capsular K antigens (type-specific polysaccharide ) and the flagellar H proteins.
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7
Q

Which of the antigens specific to Enterobacteriaceae are heat-liable? (2)

A
  • The K and H antigens. O antigen is heat-stable.
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8
Q

Which strains of Enterobacteriaceae are not motile? (3)

A
  • Klebsiella, Shigella, Yersinia.
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9
Q

How are encapsulated Enterobacteriaceae are protected by phagocytosis?

A
  • By their hydrophilic capsular antigens, which repel the hydrophobic phagocytic cell surface.
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10
Q

What is type III secretion system and which strains of Enterobacteriaceae have it? (6)

A
  • Yersinia, Salmonella, Shigella, enteropathogenic Escherichia, Pseudomonas, Chlamydia. It is a molecular syringe of 20 proteins used deliver their virulence factors into targeted eukaryotic cells.
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11
Q

What are siderophores and what are some subtypes?

A
  • Iron-chelating compounds use by bacteria like enerobactin, aerobactin.
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12
Q

What are the most important strains of E.coli? (5)

A
  • Enterotoxigenic (ETEC)
  • Enteropathogenic (EPEC)
  • Enteroaggregative (EAEC)
  • Enterohemorrhagic (EHEC)
  • Enteroinvasive (EIEC)
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13
Q

Which subspecies of E.coli affect mainly the small intestines?

A
  • Enterotoxigenic (ETEC)
  • Enteropathogenic (EPEC)
  • Enteroaggregative (EAEC)
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14
Q

Which subspecies of E.coli affect mainly the large intestines?

A
  • Enterohemorrhagic (EHEC)

- Enteroinvasive (EIEC)

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15
Q

How is the Enterotoxigenic (ETEC) E.coli transmitted?

A
  • Thru consumption of fecally contaminated food or water. Person-to-person spread does not occur.
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16
Q

What causes the Enterotoxigenic (ETEC) virulence?

A
  • The two classes of enterotoxins it produces: Heat-liable toxins (LT-I, LT-II) and the heat-stable toxins (STa and STb)
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17
Q

Which of the enterotoxins by Enterotoxigenic (ETEC) are associated with human disease?

A
  • The LT-I and the STa.
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18
Q

How does the LT-1 enterotoxin by Enterotoxigenic (ETEC) work?

A
  • Consists of one A subunit and 5 B subunits. The B subunit binds to the same receptor as the cholera toxin (GM1 gangliosides) on the surface of epithelial cells in small intestine. The A subunits enters inside, with the net effect of increase in cAMP levels with enhanced secretion of chloride and a decreased absorption of Na and Cl : Watery diarrhea.
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19
Q

How does the STa enterotoxin by Enterotoxigenic (ETEC) work?

A
  • A small monomeric peptide that binds to an membrane guanylate cyclase recepetor, increasing cGMP and subsequent hypersecretion of fluids.
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20
Q

Describe the virulence of the Enteropathogenic (EPEC)

A
  • Spreads person-to-person, invades the small intestine epithelium by effacement of the microvillus, forms small colonies medieated by bundle forming pili (BFP).
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21
Q

Describe the virulence of the Enteroaggregative (EAEC)

A
  • It is one of the few bacteria associated with chronic diarrhea and growth retardation in children, characterized by their stacked-brick (by aggregative adherence fimbriae 1 AAF1)
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22
Q

What are the 2 groups of toxins that are associated with EAEC?

A
  • Enteroaggregative heat stable toxin (EAST)

- Plasmid encoded toxin (PET)

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23
Q

What is the clinical manifestation that Enterohemorrhagic EHEC causes?

A
  • Diarrhea to hemorrhagic colitis and hemolytic uremic syndrome (HUS) to children younger than 10 years old.
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24
Q

What is the common strain of EHEC serotype?

A
  • O157:H7
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25
Q

What toxin is associated with hemolytic uremic syndrome (HUS) from the Enteroaggregative (EAEC)?

A

Stx-2

26
Q

What is the enteroinvasive EIEC strain closely resemble to?

A
  • The Shigella bacteria.
27
Q

In contrast to other E.coli strains, what does EHEC not ferment and what is the most common serotype of EHEC?

A

Sorbitol. O157

28
Q

What is the recommended treatment for patients suffering enterohemorrhagic E.coli and Salmonella?

A
  • Symptomatic relief because antibiotics can prolong the fecal carriage of these organisms or increase the risk of secondary complications.
29
Q

Describe the pathogenesis of salmonella.

A
  • Attaches to the mucosa of the small intestine and invade into the M (microfold) cells located in Peyer patches as well into enterocytes. The bacteria remain in endocytic vacuole, where they replicate.
    tem.
30
Q

Through what mechanism does Salmonella affect neighboring epithelial cells?

A

Type III secretion system

31
Q

Which Salmonella strains are highly adapted to humans?

A
  • Salmonella Typhi and Salmonella Paratyphi
32
Q

What is the reservoir for Salmonella Typhi?

A

Humans

33
Q

What does Salmonella infection cause?

A
  • Gastroenteritis: Nausea, vomiting, and nonbloody diarrhea.
34
Q

Which strain of Salmonella causes typhoid fever?

A

Salmonella Typhi

35
Q

Which strain of Salmnoella causes paratyphoid fever?

A

Salmonella Paratyphoid A, Salmonella Schottmuelleri and Salmonella Hirschfeldii

36
Q

Where is the reservoir that causes chronic colonization that causes typhoid and paratyphoid fever?

A

Gallbladder

37
Q

What organ does shigella affect?

A
  • Invading and replicating in cells lining the colon.
38
Q

Describe the pathogenesis of Shigella.

A
  • They can’t attach to differentiated mucosal cells, they first attach to and invade the M cells located in the Peyer patches and deploy type III secretion system to invade nearby epithelial cells.
39
Q

Unlike Salmonella which replicates in the host cell vacuoles, where does Shigella replicate in the host cell?

A
  • In the cytoplasm.
40
Q

How does Shigella avoid immune-mediated clearance?

A
  • Rearrangement of actin filaments of host cells, the bacteria are propelled thru the cyplams to adjacent cells where cell-to-cell passage occurs.
41
Q

Which strain of Shigella produce the exotoxin Shiga toxin?

A

S. dysenteriae

42
Q

What is the reservoir for Shigella?

A

Humans

43
Q

Which strain of Shigella is responsible for 85% of infections of Shigella in the US? And for developing countries? And for Africa and Central America?

A

S. sonnie; S. flexneri and S. dysenteriae respectively.

44
Q

How is Shigella transmitted?

A
  • Person to person thru fecal-oral route
45
Q

What are the clinical symptoms of Shigella infection?

A
  • Abdominal cramps, diarrhea, fever and bloody stools. First sign of infection is profuse, watery diarrhea without histologic evidence of mucosal invasion.
46
Q

Which strains of yersinia are medically relevant? (3)

A
  • Y. pestis, Y. enerocolitica, Y. pseudotuberculosis.
47
Q

Which strain of yersinia causes the Plague?

A
  • Y. pestis.
48
Q

What type of infection is an infection from yersinia classified as?

A
  • Zoonotic infection; humans are accidental hosts.
49
Q

What is a common characteristic of the pathogenic Yersinia speices?

A
  • Resist phagocytic killing by type III secretion system.
50
Q

Describe the mechanism of the type III secretion system of Yersinia in contact with phagocytic cell.

A
  • Secretes 3 proteins to the phagocyte: YopH gene product to dephosphorylate several proteins required for phagocytosis; YopE to induce cytotoxicity by disrupting acting filaments; YopJ/P to initiate apoptosis in macrophages.
51
Q

What are the two forms of Y. pestis infection and their perspective natural reservoirs?

A
  • Urban plague (rats) and sylvatic plague (squirrels, rabbits, field rats and domestic cats).
52
Q

What are the 2 clinical manifestations of Y. pestis?

A
  • Bubonic plague (causes bubo: inflammatory swelling of the lymph nodes) and the pneumonic plague ( fever and malaise and pulmonary sings within 1 day)
53
Q

What are the clinical sings of Y. eneterocolitica and Y. pseudotuberculosis?

A
  • Gastroenteritis which can cause pseudoappendicits
54
Q

In terms of culturing, what is a common characteristic of Yesernia?

A
  • Can grow at 4 degrees C. Most other organism are inhibited or die.
55
Q

What are the medically important strains of Klebsiella?

A
  • K. pneumoniae, K. oxytoca, K.granulomatis, K. rhioscleromatis, K. ozaenae.
56
Q

In terms of culturing, what is a common characteristic of Klebsiella?

A
  • Mucoid appearance of isolated colonies.
57
Q

What are the clinical manifestations of K. pneumoniae and K. oxytoca?

A
  • Lobular pneumonia: the one caused by Klebsiella cause necrotic destruction of alveolar spaces, formation of cavities and the production of blood-tinged sputum.
58
Q

What does the K.granulomatis cause and what is it commonly called?

A
  • Granuloma inguinale: granulomatous disease affecting the inguinal and groin area. Donovanosis.
59
Q

What does K. rhioscleromatis and K. ozaenae cause?

A
  • Granulomatous disease of the nose and chronic atrophic rhinitis, respectively.
60
Q

What does Protues mirabilis cause?

A
  • Produces large quantities of urease, which splits urea into CO2 and ammonia, raising the pH of urine, persipitating Mg and Ca, into struvite and apatite crystals respectively which in the end results in the formation of renal stones.
61
Q

What does Citrobacter koseri cause?

A
  • Predilection for causing meningitis and brain abscesse in neonates.

Hardcore Microbiology (13 decks)

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