Lecture on Enterobacteriaceae and Gram Negative Rods

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These flashcards cover key concepts, definitions, and distinctions related to the Enterobacteriaceae family and Gram negative rods discussed in the lecture.

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24 Terms

1
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What is the family of gut-associated gram-negative rods discussed in the lecture?

Enterobacteriaceae.

2
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What does 'Enterobacteriaceae' refer to in bacteriology?

It refers to a family of enteric organisms associated with the gut.

3
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Name two pathogens from the Enterobacteriaceae family that are not normal flora.

Salmonella and Shigella.

4
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Which organism is the most isolated from different microbiology cultures?

Escherichia coli (E. coli).

5
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What is the distinguishing characteristic of Enterobacteriaceae regarding their oxygen requirements?

They are facultative anaerobes, meaning they can grow with or without oxygen.

6
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Which test is used to differentiate between lactose fermenters and non-lactose fermenters on MacConkey agar?

The color change to pink for lactose fermenters indicates acid production.

7
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What are some major infections caused by members of the Enterobacteriaceae family?

Urinary tract infections, respiratory infections, and wound infections.

8
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What is the appearance of E. coli on MacConkey agar?

It forms pink colonies due to lactose fermentation.

9
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What reaction would you expect from Proteus on a TSI slant?

It would show K/A (alkaline slant with acidic butt) with H2S production.

10
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What distinguishes Shigella from Salmonella in laboratory tests?

Shigella is H2S negative, whereas Salmonella is H2S positive.

11
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What does a positive indole test indicate?

The presence of tryptophanase enzyme that breaks down tryptophan.

12
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In terms of colony morphology, how do enteric gram-negative rods typically present on agar?

They are generally larger than gram-positive colonies and can be medium to large in size.

13
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Name the three sugars present in TSI agar.

Lactose, sucrose, and glucose.

14
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What does an alkaline (red) slant with an acid (yellow) butt indicate in a TSI test?

It indicates that the organism is a non-lactose fermenter using only glucose.

15
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Why must antibiotics be used cautiously in treating Salmonella infections?

Using antibiotics can lead to the development of antibiotic resistance and may worsen the infection in the gut.

16
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What is a virulence factor for E. coli?

The presence of endotoxin (LPS), capsule, flagella, and various toxins.

17
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What is the family characteristic that allows differentiation on oxidase testing?

Most members of this family (Enterobacteriaceae) are oxidase negative.

18
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How can one isolate Salmonella from stool samples?

By using selective media such as Hektoen enteric agar or XLD agar.

19
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Which organism is recognized for swarming growth on blood agar?

Proteus.

20
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What is the primary virulence factor associated with Shigella?

The production of shiga toxin.

21
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What common method is used to diagnose bacterial infections in clinical microbiology?

Culture and isolation of microorganisms from patient samples.

22
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What is the importance of knowing the different serotypes of E. coli?

Different serotypes can have varying pathogenic properties and virulence factors.

23
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Name one characteristic that differentiates Enterobacter from Klebsiella in a microbiology lab.

Indole test: Klebsiella is typically indole negative while Enterobacter can be positive.

24
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What is the relationship between the presence of Salmonella in food animals and human infections?

Foodborne illness results from consuming contaminated animal products, leading to infections.