L4 MHD: Enterobacter I

Question 1

What bacteria cannot ferment glucose?

What bacteria is oxidase negative but CAN ferment glucose?

Answer 1

1. Pseudomonas
2. ENTEROBACTERIACEAE

(Vibronaceae is oxidase positive)

Question 2

Characteristics of Enterobacteriaceae:

1. Gram + or - ?
2. Rod or Bacilli?
3. Indigenous flora of _____
4. Colonize ______ of what patients?
5. Aerobic or anaerobic?

Answer 2

1. Gram negative
2. Rod
3. GI tract
4. Respiratory tract of hospitalized patients
5. grow rapidly BOTH aerobically & anaerobically
   - simple growth requirements

Question 3

What are the 3 components of the Enterobacteriaceae LPS endotoxn?

Answer 3

1. O Antigen
2. Core oligosaccharide
   - attaches directly to lipid A
3. LIPID A

Question 4

1. Antibodies are directed to what part of the LPS endotoxin?
2. What is the innermost region of LPS that is responsible for toxicity?
3. What causes the toxicity of this component?

Answer 4

1. O Antigen
   - 100-200 serotypes
   - outermost domain
   - polysaccharide (repeating monosaccharide trimers)
2. LIPID A
3. bacterial cells are lysed by the immune system–> fragments of membrane containing lipid A are released into the circulation, causing fever, diarrhea, and possible fatal endotoxic shock

(also called septic shock).

Question 5

1. _____ located in peritrichous FLAGELLA

(more than 50 serotypes)

2. ____ located in the CAPSULE
   (80 serotypes)

Answer 5

1. H- Antigen
   - flagellar = MOTILE
2. K - Antigen

• • K is for german word for capsule **
• prevents phagocytosis of the organism

Question 6

What is the pneumonic for bacteria that ferment LACTOSE

What are 4 common features of Enterobacter, Serratia, and Klebsiella?

Answer 6

Test with macConKEE’S
agar

C- Citrobacter
K - Klebsiella
E - Enterobacter
E - E.Coli
S - Serratia (slowly ferments lactose)

1. Multidrug resistant
2. All NOCOSOMIAL
3. Cause Pneumonia & UTI
4. ALL FERMENT LACTOSE

Question 7

What is the K antigen important for?

Answer 7

important in causing extraintestinal colonization, UTI, and invasive disease.

(reason for neonatal meningitis)

Question 8

What are 7 virulence factors of Enterobacteriaceae?
(they are described below)

1. LPS; causes fever, sepsis, shock & multigrain failure
2. Protects from phagocytosis
3. Altered expression of K, H antigens which protects from antibody mediated cell death
4. Secretion of bacterial virulence factors into host cells
5. Sequester growth factors
6. Resistance to ____
   a)
   b)

Answer 8

1. Endotoxin
2. Capsule
3. Antigenic Phase Variation
4. Type III secretion system
5. Iron Scavengers
6. RESISTANCE TO
   a) serum killing
   b) antimicrobials

Question 9

What is the structure of

Enterobacteriaceae? Color?

Answer 9

1. gram negative RODS

2. PINK on gram stain

Question 10

What are the 4 most important biochemical characteristics of Enterobacteriaceae?

TEST!!!

Answer 10

1. Facultative Gram-Neg rods
2. Ferment glucose
3. Reduce nitrate to NITRITE
4. Oxidase negative*

Question 11

What are the bacteria that ferment lactose?

What agar is used to detect this?

What color are the lactose fermenters?

What are the 4 NON-lactose fermenters that are gram neg?

Answer 11

1.
macConKEE'S agar
1. Citrobacter
2.Klebsiella
3.Enterobacter
4.E.Coli
5.Serratia

2. MacConkey Agar
   (only for gram neg.)
3. PURPLE/PINK!
4. ENTERIC PATHOGENS
   (all lactose negative)

a) Salmonella
b) Shigella
c) Proteus
d) Yersinia

Question 12

1. What are the 7 tribes?

2. What tribe does shigella fall under?

Answer 12

1. Tribe I – Escherichieae
2. Tribe II –Edwardsielleae
3. Tribe III – Salmonelleae
4. Tribe IV – Citrobactereae
5. Tribe V – Klebsielleae
6. Tribe VI – Proteeae
7. Tribe VII – Yersinieae
8. Tribe I – Escherichieae

Question 13

1. What tribe is E.COli in
2. What is its habitat?
3. What is the usually infection and how does it occur?
4. Does it ferment lactose?

Answer 13

1. Tribe I - Escherichieae
2. INTESTINES of humans & animals
   - exists in human & animal feces

• presence in water is indicator of fecal contamination
  3. UTI from our own flora
  4. YES - ferments lactose

Question 14

What are the 6 clinical symptoms of EColi?

2. It is 80% of community acquired ____

Answer 14

1. gram negative SEPSIS
2. UTI
3. Wound infections
4. Pneumonia in IC hospitalized patients*
5. Meningitis in neonates
6. GASTROENTERITIS
7. UTI -– 80% of community acquired UTIs are due to E.COli

Question 15

What organism of E.Coli is described by the following:

1. Elaboration of secretory toxins (LT, ST) that do not damage the mucosal epithelium
2. Secretory diarrhea (Traveler’s Diarrhea) similar to V. cholerae.
3. PROFUSE water diarrhea
4. Produce Heat Labile (cAmp) and Heat Stabile (cGmp) ENTEROTOXINS
5. No inflammation or Invasion

Answer 15

Enterotoxigenic
E. coli (ETEC)

• Often accompanied by mild abdominal cramps.
• Dehydration and vomiting occur in some cases

T = traveler’s

Question 16

What organism of E.Coli is described by the following:

1. Adhere to EPITHELIAL cells in localized microcolonies and cause attaching and effacing lesions
2. Usually occurs in INFANTS** (TEST)
3. No GROSS BLOOD**
4. Characterized by low-grade fever, malaise, vomiting, and diarrhea, with a prominent amount of MUCUS

Answer 16

Enteropathogenic
E. coli (EPEC)

P = pediatrics

• no toxin produced
• adheres to apical surface
• flattens villi & prevents absorption

Question 17

What organism of E.Coli is described by the following:

1. Invade epithelial cells
2. Inflammatory diarrhea
   (Dysentery) similar to Shigella.
3. Hallmarks are fever and colitis.
4. Symptoms are urgency and tenesmus

*** BLOOD, MUCUS, and many LEUKOCYTES in stool. ** (test)

Answer 17

Enteroinvasive
E. coli (EIEC)

I = invasive, dysentery

• microbe INVADE intestinal mucosa
• similar to shigella

WHITE BLOOD CELLS PRESENT!

(none in EHEC)

Question 18

What organism of E.Coli is described by the following:

1. Primarily caused by E.coli O157:H7
2. Elaboration of cyto-toxins (Shiga toxins, Stx1 and Stx2)
3. Bloody diarrhea without WBCs!!!!*** (TEST)
4. Often no fever. Abdominal pain is common.
5. May progress to hemolytic uremic syndrome (HUS)

Answer 18

Entero Hemorrhagic
E. coli (EHEC)
**Shiga Toxin producing E. coli (STEC) **

Question 19

What is the main complication of EHEC (enterohemorrhagic E.Coli?

What is absent in the diarrhea?

What is the pathogenic phenotype?

Answer 19

1. may progress to HEMOLYTIC UREMIC SYNDROME
2. WBCs!

(only found in EIEC)

3. O157:H7

Question 20

What organism of E.Coli is described by the following:

1. Adhere to epithelial cells in a pattern resembling a pile of stacked bricks
2. WATER DIARRHEA with BLOOD & MUCUS
3. vomiting, dehydration and less commonly, abdominal pain.

Answer 20

Enteroaggregative

E. coli (EAggEC)

Question 21

A college student returning from a Spring vacation in Puerto Vallarta, Mexico developed a profuse watery diarrhea accompanied by mild abdominal cramps. His diarrhea is so profuse that he is experiencing symptoms of dehydration. While on vacation he was careful not to purchase food from street vendors but did frequent the local bars and had drinks served with ice. Stool exam revealed no blood or WBC’s. What type of diarrheagenic E. coli is most likely to cause the symptoms experienced by this student?

E. coli O157
Enterotoxigenic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enteropathogenic E. coli (EPEC)
Enterohemorrhagic E. coli (EHEC)

Answer 21

Enterotoxigenic E. coli (ETEC)

T = traveler’s

Question 22

BLOODY diarrhea produced by STEC (shiga toxin producing E Coli) can progress to what?

Answer 22

Hemolytic Urea syndrom

1. thrombocytopenia
2. anemia
3. acute renal failure
micro thrombi on damaged endothelium

Question 23

How is E. Coli O157-H7 transmitted?

Answer 23

1. Shed in feces of cattle, sheep, deer (ruminants)
2. Human infection is acquired via
   - contaminated food or water, or

• via direct contact with an infected patient

Question 24

The following are modes of transmission of ______.

1. Foodborne outbreaks most commonly associated with undercooked ground beef
2. Reservoir in healthy dairy cattle (normal flora)
3. Sporadic cases assoc. with unpasteurized milk, apple cider, lettuce and other produce, petting zoos, state fair show barns, contaminated water
4. young children & elderly are at risk
5. Transmission through food, person-to-person contact, rarely, contaminated water

Answer 24

E.COli O157

• An estimated 265,000 STEC infections occur each year in the United States.
• STEC O157 causes about 36% of these infections and 60 deaths each year.

Question 25

What two MAJOR infections are associated with E.COli O157

Answer 25

1. Hemolytic Uremic Syndrome | 2. Hemorrhagic Colitis

Question 26

What are the symptoms of Hemorrhagic Colitis?(4) - specifically, what is absent from the stool Which E.Coli is this associated with?

Answer 26

1. Abdominal cramps, watery diarrhea, 2. bloody discharge 3. No significant fever 4. Absence of WBC in stool B) E.COli O157 - EHEC

Question 27

What are the triad of symptoms associated with HEMOLYTIC UREMIC SYNDROME caused by E.Coli O157 (EHEC) What is this PRECEDED by?

Answer 27

1. Acute renal failure 2. Thrombocytopenia 3. Anemia 2. Preceded by bloody diarrhea ** - Leading cause of acute renal failure in children

Question 28

How does EHEC present clinically?

Answer 28

1. three to four days of NONBLOODY diarrhea with abdominal pain 2. Onset of bloody diarrhea and severe pain - resolution in 4-10 days OR B) Hemolytic Uremic Syndrome - death - sequelae (renal impairment, hypertension, CNS damage)

Question 29

What is the hall mark of Microangiopathic hemolytic anemia? What would show up the on CBC? Why would the patient be urinating less?

Answer 29

1. SHISTOCYTES - fragmented RBC's ** MECHANICAL HEMOLYSIS** (first aid) 2. PLatelet consumption = low platelet count 3. Decreased renal blood flow = RENAL FAILURE

Question 30

Describe how Shiga toxin invades the body. (by answering the questions below) 1. What never invades the blood stream? 2. What does? 3. What does it attach to? Where? 4. Where are most of the receptors located? 5. What is deposited? 6. What is a result of this deposition? 7. ____ Increases 8. Final step?

Answer 30

O157 1. organisms never invade the blood stream, stay in the intestines 2. produce SHIGA TOXIN which invades the blood stream 3. attaches to receptors of ENDOTHELIAL CELLS on the inside lining of the vessels 4. largest # of Shiga receptors = RENAL AREA 5. Damages renal wall - body responds by depositing FIBRIN & consuming platelets 6. Lumen narrows & becomes rough 7. Blood pressure builds 8. RBCs begin to lyse = MICROANGIOPATHIC HEMOLYTIC ANEMIA

Question 31

Was is the treatment of Renal failure caused by Microangiopathic Hemolytic Anemia? (not on test)

Answer 31

1. no treatment other than life support 2. blood transfusions for anemia 3. renal dialysis 4. VENTILATE them as well

Question 32

Action of Shiga Like Toxin (O157:H7) 1. ____ inhibited 2. Damage of ____ & _____ 3. Infarction of ____ leads to bleeding into the bowel & bloody diarrhea

Answer 32

1. PROTEIN SYNTHESIS is inhibited (ribosomes at 60s) - commensal bacteria - host cells 2. Microcirculation & Mucosal damage 3. MUCOSA infarcts - bleeding into the bowel & bloody diarrhea!

Question 33

What cells are particularly sensitive to the cytokine secretion induced by Shiga like toxin (EHEC)? (2) Where? (2)

Answer 33

1. Endothelial 2. Epithelial 1. Kidney 2. CNS

Question 34

A majority of E.COli O157 Hemolytic Uremic Syndrome occur with diarrheal related cases. However, there are also non diarrheal HUS.What are 3 things this occurs in association with?

Answer 34

1. Pneumococcal infection 2. Chemotherapy 3. Transplant immunosuppresion

Question 35

RISK Factors for HUS following O157 infection. 1. Host factors (3) 2. Clinical factors (3) 3. Treatment factors (2!!!)

Answer 35

1. Very young or old age 2. Mental retardation 3. P antigen expression by RBCs** 1. Bloody Diarrhea 2. Fever 3. Increase WBCs Tx factors: 1. Use of Anti-motility agents 2. Antimicrobials other: produce STII instead of both I and II

Question 36

What is the attachment site for SHIGA toxin?

Answer 36

P antigen on RBC's and endothelial cells

Question 37

Lab diagnosis: 1. Timing? 2. Type? 3. Transport?

Answer 37

1. Early stage --> first 4 days when org. load is higher BEFORE antibiotic treatment 2. WHOLE STOOL 3. soon --> refrigerate at 4C if more than 1-2 hours

Question 38

Because stool cultures are no longer used to identify E. Coli, what is used instead?

Answer 38

ANTIGEN DETECTION - shiga toxin or O157 antigen (LPS) - Direct fecal specimen detection - Enriched broth culture detection (more sensitive) DO PCR!!!!!! FilmArrayTM Gastrointestinal Panel – Multiplex PCR

Question 39

TRUE or False: | STEC (O157) diarrhea is treated with Antibiotics & anti motility agents

Answer 39

FALSE! DO NOT GIVE EITHER OF THESE!!! - will release the Shiga toxin and endotoxin when E.COli is destructed by antibiotics treat with: 1. Oral rehydration (Gatorade, Pedialyte), supportive care, and careful monitoring of kidney function. 2. HUS and renal failure: can be managed by dialysis.

Question 40

``` A healthy 3-year-old child develops diarrhea that lasts about a week, and that is bloody for a few days. His diarrhea resolves, but he remains lethargic, and passes only a little urine. A blood smear shows fragmented red blood cells and no platelets. What etiologic agent of infection would most likely produce the signs and symptoms displayed in this case?   A) E. coli 0157 B) Campylobacter jejuni C) Salmonella typhi D) Shigella flexneri E) Yersinia enterocolitica ```

Answer 40

A) E.COli O157