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Microbiology > Enterobacteriaceae > Flashcards

Enterobacteriaceae Flashcards

Part 2

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1
Q

Enterobacteriaceae Serology

A

-Three types of antigenic determinants
-O, K, and H antigens
-Used mainly for E. coli, Klebsiella, Salmonella

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2
Q

O (somatic antigen)

A

-Associated with cell wall
- Heat stable
- Consists of lipopolysaccharides
- Used to group organisms within a genus

Example: E. coli O157: H7

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3
Q

K (capsular antigen ) & Vi Antigen

A

-Surrounds the cell wall
- Can cover the O antigen
- Heat labile
- Consists of polysaccharides
- Typical organisms with the K antigen are Klebsiella, E. coli
- Vi antigen = S. typhi

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4
Q

H (flagellar antigen)

A
  • Found in the flagella
  • Consists of protein
  • Heat labile
  • Used to serobype with the species

Example: E. coli O157: H7

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5
Q

Escherichia coli

A
  • Most common facultative organism in stool .. most normal flora
  • Colony morphology on EMB = green metallic sheen
  • Can be beta-hemolytic: Normal stool flora strains usually are
  • Colonies on MAC = dark pink colonies with pink diffusing into agar around colony” LACTOSE+
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6
Q

True or False: E. coli is most common cause of UTI and kidney infection in human

A

True

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7
Q

True or False: E. coli is one of the least common causes of septicemia and meningitis among neonates; acquired in the birth canal before or during delivery.

A

False, it is the most common causes

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8
Q

True or False: Bacteremia in adults, primarily from a genitourinary tract infection or a gastrointestinal source.

A

True

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9
Q

How many Gastroenteritis pathotypes are there in Escherichia coli?

A

There are 6 pathotypes
- Shiga-toxin producing E. coli (STEC)
- Enterotoxigenic E. coli (ETEC)
- Enteropathogenic E. coli (EPEC)
- Enteroaggregative E. coli (EAEC)
- Enteroinvasive E. coli (EIEC)
- Diffusely adherent E. coli (DAEC)

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10
Q

Shiga-toxin producing E. coli (STEC)

A
  • Produces Shiga toxin/ vero toxin
  • E. coli O157: H7 and others
    -Circulating shiga toxin binds to kidney endothelium causing inflammation
  • Inflammation and bleeding of the mucosa of the large intestine
  • Can lead to hemolytic-uremic syndrome (HUS) – resulting in damage to kidneys
    -Starts with watery diarrhea then progresses to bloody diarrhea
  • No WBC’s found in stool
  • Potentially fatal, especially in children
    -Ingestion of undercooked beef, contaminated produce
  • Lab Testing: Sorbitol negative colonies on SMAC, Serologic typing for ID
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11
Q

Other diarrheagenic E. coli - Enteropathogenic (EPEC)

A
  • primarily in infants and children
  • outbreaks in hospital nurseries and day care centers
  • stool has mucous but not blood
  • identified by serotyping
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12
Q

Other diarrheagenic E. coli - Enterotoxigenic (ETEC)

A
  • “traveler’s diarrhea” … contaminated food or water
  • watery diarrhea without blood, abdominal cramps
  • self-limiting; usually not identified
  • other than patient history and lactose-positive organisms cultured
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13
Q

Enteroinvasive (EIEC)

A

-produced dysentery with bowel penetration, invasion and destruction of intestinal mucosa
- watery diarrhea with blood
- do NOT ferment lactose
- identified via DNA probes

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14
Q

Enteroaggregative (EAEC)

A

-Cause diarrhea by adhering to the mucosal surface of the intestine
-watery diarrhea
-symptoms may persist for over two weeks

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15
Q

Diffusely adherent (DAEC)

A

-Associated with UTI’s and diarrheal disease, esp in children and pregnant women

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16
Q

Genus Shigella

A

Overt or primary pathogen, transmission only human to human

-Cause dysentery (blood stools, mucous, and numerous WBC)

  • Endotoxin*****look at notes
17
Q

True or False: All Shigella isolates must be serotyped

A

True, based on the O antigen present to divide into four serotypes (A, B, C, D)

  • If the organism shows no agglutination, then the organism must be heated (to destroy K antigen) and retested.
18
Q

What are the four species (serotypes) of Genus Shigella?

A
  • Shilgella dysenteries - Group A (most severe)
  • Shigella flexneri - Group B
  • Shigella boydii - Group C
  • Shigella sonnei - Group D (least severe)

Pneumonic for learning the four species: Dirty Fingers Bring Shigella

all cause dysentery

19
Q

True or False: Salmonella infections result in varying degrees of gastroenteritis enteric fever

A

True, (rare in U.S.)

20
Q

True or False: Most infections caused by ingestion of contaminated food, water, handling of pets.

A

True

21
Q

True or False: Carriers (those individuals with previous infection) harbor the organism asymptomatically in the gall bladder and shed organism in feces

A

True

22
Q

Genus Salmonella - Gastroenteritis

A

Salmonella enterica ssp. enterica -

  • Mild to fulminant diarrhea accompanied by low-grade fever, nausea and diarrhea
  • No invasion of blood stream
  • Occurs 8 to 36 hours after ingestion
  • Symptoms include vomiting, chills, watery diarrhea and abdominal pain
  • Requires a high microbial load for infection
  • Self-limiting in healthy individuals
  • Antibiotics may prolong carrier state
23
Q

Salmonella serotype - Typhi

A

Most pathogenic Salmonella species

Typhoid fever symptoms
- High fever
- Headache
- Weakness
- Dry cough
- Stomach pain
- Constipation
-Rashes

24
Q

Genus Edwardsiella - Edwardsiella tarda

A
  • Species associated with opportunistic human infections.
  • Involved in bacteremia and wound infections
  • May be associated with intestinal disturbances
  • Found in animal sources (reptiles, fish, birds, etc.)
  • Identification: KIA K/A (with H2S+), Indole +, Citrate =, Urea =, LDC+
25
Q

Genus Yersinim - Yersinim pestis

A
  • Plague
  • Bubonic – painful “bubo” (inflammatory swelling of the lymph node)
  • Pneumonic - can be transmitted person to person (Secondary to bubonic - organisms multiply in bloodstream and resp. tract)
    -Vector is rat flea carried by rodents
    -Humans - accidental host
    -Select Agent* CDC form 4
26
Q

Genus Yersinia - Yersinim enterocolitica

A

-Mainly causes acute gastroenteritis with fever, headaches (more common in children )

  • Human infected by ingestion of contaminated food or water
  • Is able to survive refrigerator temperatures (can use “cold enrichment” to isolate)

-can mimic appendicitis
-some infections result form eating contaminated market meat and vacuum-packed beef

27
Q

Genus Yersinia Identification (Gram stain, Selective Agar)

A
28
Q

Yersinia Identification

A
29
Q

Genus Serratia - opportunistic

A

-Serratia marcescens
-Often colonizes hospitals
-Some stains are chromogenic producing a red pigment at room temperature

30
Q

Genus Klebsiella - K. pneumoniae

A

-Opportunistic pathogen
-Destructive pneumonia with necrosis or hemorrhage ( sputum red or ‘currant jelly-like’)
-Health care associated infection

31
Q

Genus Klebsiella - K. oxytoca

A

-Opportunistic pathogen

32
Q

Genus Hafnia

A

-Opportunistic
-Hafnia lave only species
-Has been isolated from any anatomical sites in humans and the environment
-Occasionally isolated from stools
-Delayed citrate reaction is major characteric

33
Q

Genus Citrobacter

A

-Opportunistic pathogen
-Most ferment lactose and hydrolyze urea slowly
-NLF strains may resemble Salmonella

34
Q

Genus Proteus, Morganella, Providencia

A

-Opportunistic pathogens
-All are lactose negative
-Urea postive
-Deaminated phenylalanine and tryptophan (PAD/TDA = positive)

35
Q

Genus Proteus

A

-Swarming motility
- Lactose negative, but vary for sucrose
- Resistant to tetracycline

36
Q

Genus Providencia

A

-Providencia rettgeri
- Providencia stuartii (UTI, can cause nosocomial outbreaks
-Does NOT swarm

37
Q
A

Microbiology (1 decks)

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