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P2: Bacteriology > Enterobacteriaceae > Flashcards

Enterobacteriaceae Flashcards

1
Q

Pathogenesis:

E. coli is widely recognized as the most common cause of UTIs in humans

A

Uropathogenic E. coli (UPEC)

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2
Q

Virulence factors of Escherichia coli

A

PILI
CYTOLYSIN
AEROBACTIN

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3
Q

adhere to epithelial cells and not be washed out with urine flow.

A

PILI

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4
Q

kill immune cells and inhibit phagocytosis and chemotaxis

A

CYTOLYSIN

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5
Q

allow bacterial cells to chelate iron

A

AEROBACTIN

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6
Q

5 MAJOR CATEGORIES in Gastrointestinal Pathogens of Escherichia coli

A

I. Enterotoxigenic Escherichia coli (ETEC)
II. Enteroinvasive Escherichia coli (EIEC)
III. Enteropathogenic Escherichia coli (EPEC)
IV. Enterohemorrhagic Escherichia coli (EHEC)
V. Enteroadherent Escherichia coli, which includes:
a. diffusely adherent Escherichia coli (DAEC)
b. enteroaggregative Escherichia coli (EAEC).

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7
Q

ENTEROADHERENT E. coli infections:

A

Diarrheal syndromes (absence of WBCs and RBCs) & UTI

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8
Q

types of ENTEROADHERENT E. coli:

Associated with both UTI and GIT infections

A

DAEC (Diffusely Adherent E. coli)

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9
Q

types of ENTEROADHERENT E. coli:

Causes cystitis in children and acute pyelonephritis in pregnant women

A

DAEC (Diffusely Adherent E. coli)

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10
Q

types of ENTEROADHERENT E. coli:

Causes diarrhea by adhering to the surface of intestinal mucosa

A

EAEC (Enteroaggregative E. coli)

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11
Q

types of ENTEROADHERENT E. coli:

Adheres to HEp2 cells, packed in a “stacked-brick” pattern

A

EAEC (Enteroaggregative E. coli)

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12
Q

ENTEROTOXIGENIC E. coli infection:

A

Traveler’s diarrhea a.k.a Montezuma’s revenge or La Tourista

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13
Q

Colonization of ENTEROTOXIGENIC E. coli

A

Proximal small intestines

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14
Q

Infective dose of ENTEROTOXIGENIC E. coli

A

10^6 to 10^10

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15
Q

ENTEROTOXIGENIC E. coli Produces two (2) toxins:

A

Heat-labile Toxin (LT)
Heat-stable Toxin (ST)

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16
Q

ENTEROTOXIGENIC E. coli toxins:

Similar to choleragen toxin from Vibrio cholera

A

Heat-labile Toxin (LT)

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17
Q

ENTEROTOXIGENIC E. coli toxins:

Activates adenylate cyclase causing hypersecretion of both electrolytes and fluids into the intestinal lumen leading to water diarrhea

A

Heat-labile Toxin (LT)

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18
Q

ENTEROTOXIGENIC E. coli toxins:

Stimulates guanylate cyclase which leads to hypersecretion of electrolytes and water into the intestinal lumen

A

Heat-stable Toxin (ST)

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19
Q

ENTEROINVASIVE E. coli infection:

A

Dysentery-like/Shigella-like Infection;
Water diarrhea with WBCs

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20
Q

Infective dose of ENTEROINVASIVE E. coli

A

> 10^6

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21
Q

(E. coli)
Pathogenesis:
Produces dysentery with direct penetration, invasion and destruction of the intestinal mucosa

A

EIEC: ENTEROINVASIVE E. coli

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22
Q

Infection of EPEC: ENTEROPATHOGENIC E. coli

A

Infantile Diarrhea

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23
Q

(Escherichia coli)

Stool typically contains large amount of mucus but apparent blood is not
present

A

EPEC: ENTEROPATHOGENIC E. coli

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24
Q

(Escherichia coli)

Lacked the toxins of ETEC and lacks the invasiveness of EIEC

A

EPEC: ENTEROPATHOGENIC E. coli

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25
Q

Pathogenesis of EPEC: ENTEROPATHOGENIC E. coli

A

Adhesive property – attach to the borders of the intestinal cells

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26
Q

EHEC: ENTEROHEMORRHAGIC E. coli is also known as:

A

Verotoxic E. coli (VTEC) / STEC

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27
Q

Infection of EHEC: ENTEROHEMORRHAGIC E. coli

A

Hemorrhagic colitis,
HUS,
Bloody diarrhea without WBC

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28
Q

(Escherichia coli)

Associated with ingestion of poorly cooked meats

A

EHEC: ENTEROHEMORRHAGIC E. coli

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29
Q

Virulence Factors of EHEC

A

Verotoxin I
Verotoxin II

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30
Q

Virulence Factors of EHEC:

Identical to Shiga toxin produced by S. dysenteriae

A

Verotoxin I

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31
Q

Virulence Factors of EHEC:

Can be neutralized by antibodies to Shiga toxin

A

Verotoxin I

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32
Q

Virulence Factors of EHEC:

A

Biologically similar but immunologically different from Shiga toxin and Verotoxin I

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33
Q

E. coli strain serotype of hamburger-disease (EHEC)

34
Q

E. coli strain serotype Associated with hemorrhagic diarrhea and HUS

A

0157:H7 (Hamburger-disease)

35
Q

Tests for EHEC

A

• MUG test (neg) and Sorbitol non-fermenter
• SMAC: colorless colonies
• Stool examination: Stool of patients with EHEC contains no WBCs

36
Q

(Escherichia coli)

Culture identification

A

MacConkey
EMB

37
Q

Culture of E. coli where pink-red (lactose-fermenting) colony with surrounding area of precipitated bile salts

38
Q

Culture of e-coli where there is an appearance of green metallic sheen

39
Q

IMViC REACTION of Escherichia coli

40
Q

Escherichia coli
IDENTIFICATION: BIOCHEMICAL REACTIONS

To differentiate bacteria based on their ability to ferment glucose, lactose and/or sucrose, and to reduce sulfur to hydrogen sulfide.

A

TSI ( TRIPLE SUGAR IRON)

41
Q

TSI ( TRIPLE SUGAR IRON)

It is indicative of dextrose fermentation only.

A

alkaline/acid (red slant/yellow butt)

42
Q

TSI ( TRIPLE SUGAR IRON)

It indicates the fermentation of dextrose, lactose and/or sucrose.

A

acid/acid (yellow slant/yellow butt)

43
Q

TSI ( TRIPLE SUGAR IRON)

Absence of carbohydrate fermentation results.

A

alkaline/alkaline (red slant, red butt)

44
Q

TSI ( TRIPLE SUGAR IRON)

Occurs in the presence of H2S

A

Blackening of the medium

45
Q

TSI ( TRIPLE SUGAR IRON)

Bubbles or cracks in the agar indicate the production of

A

gas ( formation of CO2and H2)

46
Q

Escherichia coli
IDENTIFICATION: BIOCHEMICAL REACTIONS

TSI

A

• Fermentsglucose,lactose,sucrose
• Withgasproduction
• DoesNOTproduceH2S

47
Q

Escherichia coli
IDENTIFICATION: BIOCHEMICAL REACTIONS

ONPG TEST

48
Q

Escherichia coli
IDENTIFICATION: BIOCHEMICAL REACTIONS

Urease

49
Q

tests organisms for the ability to deaminate lysine or decarboxylate lysine.

A

LIA (Lysine iron agar)

50
Q

Lysine Decarboxylation (detected in butt):

POSITIVE

A

Purple slant/purple butt (alkaline)

51
Q

Lysine Decarboxylation (detected in butt):

NEGATIVE

A

Purple slant/yellow butt (acid)

52
Q

Lysine Decarboxylation (detected in butt):

the butt reaction may be masked by H2S production

53
Q

Lysine Decarboxylation (detected in butt):

fermentation of glucose only

54
Q

Lysine Deamination (detected on slant):

Positive
Negative

A

+ : Red slant
- : Slant remains purple

55
Q

H2S Production:

Black precipitate

56
Q

H2S Production:

No black color development

57
Q

H2S Production:

demonstrated by the presence of bubbles or cracks in the medium

A

Gas production

58
Q

Primary Intestinal Pathogens

A

Salmonella
Shigella
Yersinia

59
Q

The most pathogenic enterobacteria for humans causing enteric fever and acute gastroenteritis

A

Salmonella

60
Q

In humans; the cause of two diseases called salmonellosis:

resulting from bacterial invasion of the bloodstream

A

enteric fever (typhoid)

61
Q

In humans; the cause of two diseases called salmonellosis:

resulting from a foodborne infection/intoxication

A

acute gastroenteritis

62
Q

MOT:
- Ingestion of contaminated animal food products or improperly cooked poultry, milk, eggs and dairy products

A

Salmonella

63
Q

Salmonella spp.
VIRULENCE FACTORS

A

• FIMBRIAE
• EXOTOXIN

64
Q

Salmonella spp.

ANTIGENIC STRUCTURES

A

Somatic or O antigens
Flagellar or H antigens
Vi surface antigen

65
Q

Salmonella spp.

MAC

A

clear, colorless colonies

66
Q

Salmonella spp.

HEA (Hektoen – Enteric Agar)

A

Green colonies with black centers

67
Q

Salmonella spp.

XLD (Xylose – Lysine – Deoxycholate)

A

Red colonies with black centers

68
Q

Preferred medium for S. typhi – produces metallic colonies with ring

A

BSA (Bismuth Sulfite Agar)

69
Q

Salmonella spp.

SSA (Salmonella Shigella Agar)

A

Colorless colonies with black center

70
Q

THREE (3) GENERAL CATEGORIES OF SALMONELLA INFECTION

A

I. Enteric fever
II. Gastroenteritis
III. Bacteremia

71
Q

Causative agent for Typhoid fever

72
Q

Salmonella spp. CLINICAL SIGNIFICANCE

MOT: Ingestion of contaminated food originating from infected individuals or carriers; direct transmission through fomites is also possible

A

Enteric fever

73
Q

Salmonella spp. CLINICAL SIGNIFICANCE

Symptoms: malaise, anorexia, lethargy, myalgia and continuous frontal dull headache, “rose- spots” appear during the 2nd week of fever

A

Enteric fever

74
Q

Salmonella spp. CLINICAL SIGNIFICANCE

Complications: necrotizing cholecystitis and Peyer’s patches

A

Enteric fever

75
Q

Salmonella spp. CLINICAL SIGNIFICANCE

One of the most common forms of food poisoning

A

Gastroenteritis

76
Q

Causative agent of gastroenteritis

A

S. enterica subsp. Enterica

77
Q

Peanut-butter outbreak causative agent

A

S. sero. Typhimurium

78
Q

Salmonella spp. CLINICAL SIGNIFICANCE

Used of contaminated cooking utensils that can spread the bacteria to other food and inadequate refrigeration

A

Gastroenteritis

79
Q

Salmonella spp. CLINICAL SIGNIFICANCE

Sources of infection: Poultry, dairy products and handling of pets

A

Gastroenteritis

80
Q

Salmonella spp. CLINICAL SIGNIFICANCE

Symptoms: nausea, vomiting, chills, watery diarrhea and chills

A

Gastroenteritis

81
Q

Salmonella spp. CLINICAL SIGNIFICANCE

Occurs with and without extraintestinal foci of infection caused by nontyphoidal Salmonella (S. Typhimurium, S. Paratyphi, and S. Cholerasuis)

A

Bacteremia

82
Q

Salmonella spp. CLINICAL SIGNIFICANCE

Characterized by: Prolonged fever and intermittent bacteremia

P2: Bacteriology (11 decks)

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