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GI Micro > E. Coli > Flashcards

E. Coli Flashcards

1
Q

E. Coli, Salmonella, Shigella, and other Opportunistic Enterobacteriaceae are all what type of bacterium?

A

Gram negative facultative anaerobic rods so they ferment glucose, they are oxidase negative, and reduce nitrates to nitrite (dipstick test!)

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2
Q

What antigenic structures are used in serotyping E. Coli, Salmonella, Shigella, and other Opportunistic Enterobacteriaceae?

A

K (capsular) antigens: capsular polysaccharide (Klebsiella)
H (flagellar) antigens
O antigens: O-side of LPS chains

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3
Q

How are E. Coli, Salmonella, Shigella, and other Opportunistic Enterobacteriaceae cultured and identified?

A

Fecal samples on MacConkey
Normally sterile samples cultured on rich media
ID by biochemical tests or serology

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4
Q

On a KIA slant what does it mean if the results are Y/Y?

A

Lactose fermentation; E. Coli

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5
Q

On a KIA slant what does it mean if the results are R/Y?

A

Glucose fermentation; Shigella

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6
Q

On a KIA slant what does it mean if the results are Black?

A

Hydrogen Sulfide production; Proteus

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7
Q

On a KIA slant what does it mean if the results are R/R?

A

No fermentation; Pseudomonas

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8
Q

On a KIA slant what does it mean if the results have a bottom gap?

A

H2 production; E. Coli

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9
Q

What is a big problem for the treatment of E. Coli, Salmonella, Shigella, and other Opportunistic Enterobacteriaceae?

A

Plasmid-mediated antibiotic resistance, although antibiotics are generally not needed

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10
Q

What percentage of infectious diarrhea is caused by viruses?

A

90

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11
Q

If diarrhea persists more than 10-14 days what is it most likely?

A

A parasite

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12
Q

If diarrhea is chronic what should begin to be considered?

A

HIV; it is a big problem in AIDS patients

Mycobacterium avium intracellulare, CMV

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13
Q

What diseases does E. Coli cause?

A

Diarrhea and dysentery, a variety of opportunistic infections (#1 cause of UTIs) including septicemia and meningitis in neonates

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14
Q

Where is E. Coli important (regionally)?

A

In the US and developing world

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15
Q

Why do resident E. Coli flora not cause diarrhea?

A

They lack PAIs

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16
Q

What are the cultural characteristics of E. Coli?

A

Lac+, ferments glucose with gas (H2), does not produce H2S, motile

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17
Q

What are the cultural characteristics of Salmonella?

A

H2S+, Gas + (except S. typhi) Lac -, Glu +

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18
Q

What are the cultural characteristics of Shigella?

A

H2S-, Gas -, Lac -, Glu +

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19
Q

What are the 5 types of E. coli?

A 
Enterotoxigenic (ETEC)
Enteroinvasive (EIEC)
Enterohemorrhagic (EHEC)
Enteropathogenic (EPEC)
Enteroaggregative (EAEC)
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20
Q

What is EHEC caused by?

A

Mostly by O157:H7; Undercooked beef, fruits, unpasteurized juices, lettuce, spinach, sprouts, and human to human

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21
Q

What are the symptoms of EHEC?

A

Little fever, acute onset cramps, watery diarrhea that becomes bloody within 24 hours (noninflamm, no leukocytes); Lasts up to 8 days

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22
Q

What is the pathogenesis of EHEC?

A

Low infectious dose (~100), Shiga toxin (Stx) which is an AB toxin that cleaves 28S RNA of the ribosome where the lysogenic phage is encoded

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23
Q

What is the important syndrome that follows in about 2-7% of patients? (EHEC)

A

HUS; HUS and EHEC is the MCC of pediatric acute renal failure; think young and elderly; also anemia. DONT TREAT with abx because it is exacerbated

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24
Q

What is the locus of enterocyte effacement for EHEC?

A

It is a PAI with a type 3 secretion system, it delivers E. coli receptor to host cell, makes pedestal for attachment, and responsible for the diarrhea

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25
Q

How is EHEC diagnosed?

A

O157:H7 cannot use sorbitol so:
White on Sorbitol MacConkey agar
other STEC and E. coli are red/pink
RADT for Stx in stool

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26
Q

Why are Abx CI’d in EHEC?

A

Believed to stress bacteria leading to increased phage expression of Stx

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27
Q

What is ETEC?

A

Traveler’s diarrhea

28
Q

What are the virulence factors for ETEC?

A

CFA I or II for attachment

29
Q

What are the symptoms of ETEC?

A

High volume watery diarrhea (but nowhere near as much as cholera)

30
Q

What are the 2 toxins of ETEC process?

A

Heat labile toxin (LT) lie cholera toxin (same mech too as cholera too!); and Heat stabile toxin (ST); net effect is both lead to hyper secretion of chloride and water

31
Q

What is EIEC?

A

Very similar to shigella (Lac-, nonmotile) and produces Dysentery similar to Shigellosis

32
Q

What is the virulence of EIEC?

A

High infectious dose, actin tails actually push it through from cell to cell (more in shigella)

33
Q

What are EPEC symptoms?

A

Profuse, watery infant diarrhea in developing countries

34
Q

What is the virulence of EPEC?

A

Clustered micro colonies in SI that degenerate with loss of brush border and microvilli, pedestal because of LEE, no Stx, ST, or LT; attachment and effacing lesion

35
Q

Why is E. coli hospital acquired?

A

Because they are commonly isolated, and are multi drug resistant and can cause sepsis

36
Q

What is associated with an encapsulated strain (K1 antigen)?

A

Neonatal meningitis

37
Q

What us UPEC?

A

Uropathic E. Coli, it causes >90% of UTIs; more common in females than males; symptoms are same as a UTI; Dx made by bacterial in urine (10^5 in females and 10^3 in males); virulence includes a P fimbriae (PAP pili) and a capsule (K antigen)

38
Q

Salmonella and Shigella are both what type of pathogens?

A

Frank pathogens (isolation is always significant)

39
Q

What disease is Salmonella a significant source of?

A

Gastroenteritis from food poisoning

40
Q

What disease is S. Typhi known for?

A

Typhoid fever, a disseminated disease. It does NOT cause gastroenteritis

41
Q

What culturing characteristics will be found with Salmonella?

A

Gram -, Lac -, Glu +, produces gas (not typhi), and H2S +

42
Q

What is the only significant species of Salmonella?

A

S. Enterica

43
Q

What is Salmenellosis caused by?

A

S. Enteriditis, Typhimurium, and other non-Typhi; Enteriditis and Typhimurium are the two most frequent

44
Q

What is Salmonellosis and where does it come from?

A

It is GE that is grossly underreported, caused by meat products, dairy, poultry and EGGS, pet turtles/reptiles, and human - human transmission

45
Q

Describe what happens after consumption of S. Enteritidis.

A

Bacteria swim through intestinal mucosa layer and reach the small bowel; they are encoded with PAI Type 3 system and inject effectors into M cells that form membrane ruffles that endocytose bacteria, bacteria cross to basal membrane and enter lamina propria - inflammatory response ensues

46
Q

When do symptoms of Salmonellosis begin and what do they consist of?

A

20-72 hours post consumption and with N/V followed by abdominal cramps and diarrhea lasting 3-4 days (fever in half, diarrhea can be loose to dysentary) - abx usually not necessary

47
Q

Can Disseminated Salmonellosis happen?

A

Yeah, but it’s rare

48
Q

What does disseminated salmonellosis consist of and who gets it?

A

Bactermia, sepsis; osteomyelitis; endocarditis; renal problems. AIDS and Hodgkin’s patients (bacteremia), sickle cell children (osteomyelitis), and the elderly/very young

49
Q

What is Typhoid fever caused by, and how is it spread?

A

S. Typhi, fecal-oral route, exclusively human reservoir (infected food handler)

50
Q

How does S. Typhi infect?

A

Invade M cells, survive in macrophages because the Vi capsule antigen inhibits neutrophil uptake - then spreads to mesenteric lymph nodes and RES in macrophages - then spread to blood (sepsis). Perforations of GI tract at necrotic peyer’s patches can lead to hemorrhage

51
Q

What are the symptoms of Typhoid Fever?

A

Insidious, rising fever with headache and abdominal pain (slow pulse and confusion, diarrhea late if at all, death possible by ruptured spleen); chronic gallbladder infection is possible

52
Q

Where is typhi cultured from?

A

From blood or feces

53
Q

Is there a vaccine for typhi?

A

Yea

54
Q

What are the 3 types of Shigella?

A

Dysenteriae, Sonnei, Flexneri

55
Q

Where is S. Dysenteriae found and what does it cause?

A

Central/South America (produce 1000x Stx compared to other shigella); HUS, and high fatality rate

56
Q

Where is S. Sonnei found?

A

70% in US, mostly children

57
Q

Where is S. Flexneri found?

A

2nd MC US, MC Worldwide, Gay men (STD)

58
Q

How is shigella transmitted?

A

It is a frank pathogen, human reservoir, fecal-oral route, most common in children, institutions, and gay men (The Penn State Special…)

59
Q

What are the culture findings for Shigella?

A

Gram -, non-motile rod, Lac -, Glu +, no gas, no H2S, Leukocytes in stool samples

60
Q

What is shigellosis?

A

Acute inflammatory colitis and bloody diarrhea - dysentery like EIEC (Sonnei is often less bloody and more watery)

61
Q

How does shigella infect?

A

Very low infectious dose (10-100 cfu), entry into M cells of the gut and escape the phagocytic vesicle, extension to neighboring enterocyte and rarely leaves the GI tract

62
Q

How is shigella cultured?

A

On standard enteric media

63
Q

What is Yersinia Enterocolitica?

A

A gram - coccobaccilli with bipolar staining

64
Q

Where is Y. Enterocolitica found?

A

Animal pathogens; human outbreaks linked to consumption of milk and pork in US

65
Q

What does Y. Enterocolitica cause?

A

Gastroenteritis, relatively rare, abdominal pain can mimic appendicitis = “pseudoappendicits”; self limiting

66
Q

What does Klebsiella Pneumoniae cause?

A

a “currant jelly” pneumonia (encapsulated), found in alcoholics (aspiration)

67
Q

What does Proteus and Morganella cause?

A

UTI’s

GI Micro (7 decks)

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