Mod 4 Enterobacterales

Question 1

What are the 3 critical shared family traits of Enterobacterales?

Answer 1

1. Oxidase negative
2. Ferment Glucose
3. Reduce nitrate to nitrite.

Question 2

Where in humans do Enterobacterales normally like to inhabit?

Answer 2

Enterobacterales, a large group of microorganisms, normally inhabit the gastrointestinal tract of humans, are associated with human infections, or are simply environmental contaminates (soil, water, or decaying matter).

Question 3

What is the clinical significance of E.coli?

Answer 3

1. Most common cause of UTIs.
2. Nosocomial infections
3. Meningitis
4. Sepsis

Question 4

Why is E.coli called uropathogenic (UPEC)?

Answer 4

E.coli possess:
1. Fimbriae and pili to specific receptors on epithelial cells of the bladder and upper urinary tract.
2. Hemolysin production results in cytokine release and inflammatory responses.

Question 5

What assists E.coli in virulence?

Answer 5

1. Release of endotoxins
2. Sometimes capsule production.

Question 6

What is the clinical significance of Klebsiella spp.?

Answer 6

Klebsiella spp. can cause:
1. Primary pneumonia in immunocompromised patients.
2. UTI’s in catheterized patients.
3. Wound infections
4. Toxin producing strains which then cause diarrheal disease.

Question 7

Can Klebsiella spp. cause resistance in other genera?

Answer 7

Yes, Klebsiella can cause plasmid mediated transfer of antimicrobial resistance to other genera.

Question 8

What is the clinical significance of Enterobactor spp.?

Answer 8

Enterobactor is an opportunist pathogen that can cause:
1. Wound infections
2. Respiratory infections
3. Septicemia
4. Occasionally meningitis.

Question 9

What is the clinical significance of Citrobactor spp.?

Answer 9

Opportunistic pathogen that can cause:
1. Diarrheal disease through enterotoxin production
2. Meningitis
3. Brain abcesses

Question 10

What is the typical colonial morphology of E.coli and BA and MAC?

Answer 10

BA: Lg gyop Beta-hem (usually but not always)
MAC: Lactose Fermenter (LF)

Question 11

What are the tests in IMViC?

Answer 11

I = Indole
M = Methyl Red
V = Voges Proskauer
C = Citrate

Question 11

What are E.coli’s IMViC results?

Answer 11

E.coli IMViC results would be
+ + - -

Question 11

What is Klebsiella’s typical BA morphology?

Answer 11

Klebsiella BA Morph:
Lggy mucoid

Question 11

Why is Klebsiella mucoid?

Answer 11

Klebsiella has the K antigen which gives it a capsule.

Question 11

How does Klebsiella test for motility?

Answer 11

Klebsiella is non-motile.

Question 12

What is one difference between Enterobacter and Klebsiella?

Answer 12

Enterobacter is motile while Klebsiella is not.

Question 13

Where can Salmonella spp. be found (reservoirs)?

Answer 13

Reservoirs for Salmonella include: Poultry, mammals, and amphibians/reptiles.

Question 14

How does infection with Salmonella spp. occur?

Answer 14

Infection occurs with improper handling of food or animals.

Control is via proper sanitation and food handling.

Question 15

What is required when Salmonella is found in the hospital laboratory?

Answer 15

Full biochemical identification followed by serotyping required.

Question 16

What are the major disease states that Salmonella can cause?

Answer 16

1. Enteric fever (early constipation to bloody diarrhea)
2. Septicemia (high fever, no GI symptoms)
3. Enterocolitis (nausea, vomiting, and diarrhea)

Question 17

How can enteric fever caused by Salmonella progress pathogenicity?

Answer 17

Ingested Salmonella in the small intestine penetrate the GI mucosa, from there it can enter the bloodstream and lymphatics and go to a variety of organs.

Question 18

What broth can be used to isolate Salmonella and why?

Answer 18

Selenite broth

Selenite broth has chemicals such as sodium
tetrathionate and sodium
desoxycholate that inhibit everything else but Salmonella (as it is resistant to it).

Helps the lab find Salmonella in stool samples.

Question 19

What is the clinical significance of Shigella spp.?

Answer 19

1. Humans are reservoirs of infection.
2. Causes dysentery.
3. Low infectious dose (10-100 bacteria)
4. Four species in group (serogroup)

Question 20

What is the clinical significance of Yersinia spp.?

Answer 20

1. Human and animals reservoirs of infection.
2. Associated with pork consumption.
3. Can cause enteric disease.
4. Often isolated in young children than adults.
5. Grows optimally at room temperature and can survive at 4C.

Question 21

What is similar between Aeromonas spp. and Enterobacterales? What is an important difference?

Answer 21

Aeromonas spp. has similar pathogenicity and colonial morphology (beta-hem too) to E.coli in the Enterobacterales order but the key difference is that it is Oxidase Positive!

Question 22

What organisms are in the “PMP group”?

Answer 22

PMP Group:
Proteus spp.
Morganella spp.
Providencia spp.

Question 23

What is the clinical significance of the PMP group?

Answer 23

It is an opportunistic pathogen causes illness in mainly immunocompromised patients.

Question 24

What is a key test for the PMP group?

Answer 24

The PMP group is all positive for phenylalanine deaminase.

Question 25

What is the clinical significance of Serratia spp.?

Answer 25

Opportunistic pathogen that may cause:
1. Pneumonia
2. Septicemia (especially in patients receiving chemotherapy).