Salmonella Isolation Steps

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Questions and Answers

What is the primary purpose of the initial inoculation of the sample into a non-inhibitory liquid medium?

To favor the repair and growth of stressed or sublethally-injured salmonellae cells (correct)

To inhibit the growth of competing microorganisms

To promote the death of Salmonellae cells

To select for the proliferation of Salmonellae

What is the main difference between the preenrichment broth and the enrichment broth?

The enrichment broth is more toxic to Salmonellae

The preenrichment broth is more nutritious for Salmonellae

The enrichment broth is more selective for Salmonellae (correct)

The preenrichment broth is more selective for Salmonellae

What is the term used to describe the process of transferring a portion of the sample from the preenrichment broth to the enrichment broth?

Preenrichment

Subculturing

Inoculation

Selective Enrichment (correct)

What is the ultimate goal of the selective enrichment process?

To identify the presence of Salmonellae in the sample Signup and view all the answers

What is the consequence of not providing a non-inhibitory liquid medium for the initial inoculation of the sample?

Stressed or sublethally-injured Salmonellae cells will not recover Signup and view all the answers

What is a characteristic of most Salmonella serotypes?

They are pathogenic Signup and view all the answers

What is the primary purpose of non-selective enrichment in Salmonella isolation?

To enhance the growth of Salmonella serotypes Signup and view all the answers

At which stage of Salmonella isolation is non-selective enrichment typically used?

During pre-enrichment Signup and view all the answers

What is a benefit of using non-selective enrichment in Salmonella isolation?

It reduces the risk of false-negative results Signup and view all the answers

What is the primary goal of the pre-enrichment step in Salmonella isolation?

To increase the recovery of Salmonella serotypes Signup and view all the answers

What is the purpose of using selective differential agars in selective plating enrichment cultures?

To isolate salmonellae from other microorganisms Signup and view all the answers

What is the primary goal of purification in Salmonella isolation?

To obtain a pure culture of Salmonella for further testing Signup and view all the answers

Which of the following media is used for the purification of presumptive Salmonella isolates?

MacConkey agar plates or SS agar plates Signup and view all the answers

What is the purpose of selective plating enrichment cultures in Salmonella isolation?

To isolate Salmonella from other microorganisms Signup and view all the answers

What is the expected outcome of using selective differential agars in Salmonella isolation?

The isolation of presumptive Salmonella isolates Signup and view all the answers

What is the primary purpose of selective plating in the given context?

To isolate and separate the bacteria from the sample Signup and view all the answers

What is the significance of using XLD Agar in selective plating?

It is a selective medium for certain bacteria Signup and view all the answers

What is the recommended temperature for incubating the XLD Agar plate?

37 oC Signup and view all the answers

What is the purpose of taking a loopful from SCB?

To transfer the bacteria to the XLD Agar plate Signup and view all the answers

How long is the XLD Agar plate incubated at 37 oC?

24 hours Signup and view all the answers

What is the function of the three types of sugars present in Kligler's agar?

To detect the ability of Salmonella to ferment various sugars Signup and view all the answers

What is the characteristic of Salmonella growth on XLD or SS agar?

It ferments glucose and sucrose, but not lactose Signup and view all the answers

What is the result of Salmonella growth on Kligler's agar?

Production of H2S gas that reacts with ferrous sulfate Signup and view all the answers

What is the purpose of streaking and stabbing a typical colony from XLD or SS agar onto Kligler's agar slopes?

To detect the ability of Salmonella to ferment various sugars Signup and view all the answers

What is the characteristic reaction of Salmonella with ferrous sulfate on Kligler's agar?

Production of a black colored ferrous sulfide Signup and view all the answers

Study Notes

Isolation Steps

Most Salmonella serotypes are pathogenic
Non-Selective Enrichment (Pre-enrichment) is the initial step, where the sample is inoculated into a non-inhibitory liquid medium to favor the repair and growth of stressed or sublethally-injured Salmonella cells
Selective Enrichment follows, where a portion of the sample is transferred to an enrichment broth that favors the proliferation of Salmonellae and inhibits the growth of competing microorganisms
Selective plating enrichment cultures are streaked onto selective differential agars for the isolation of Salmonellae
Purification is done on MacConkey agar plates or SS agar plates to purify presumptive Salmonella isolates
Selective Plating involves taking a loopful from SCB and streaking on the surface of XLD Agar and incubating at 37°C for 24h

XLD and SS Agar

XLD and SS agar are used for selective plating
Salmonella colonies on XLD or SS agar have a typical appearance

Biochemical Identification

Kligler's agar (Triple sugar Iron agar) slopes are used for biochemical identification
The medium contains three different types of sugars: sucrose, lactose, and glucose
A typical colony from XLD or SS agar is streaked and stabbed in the slopes
Salmonella is capable of fermenting glucose and sucrose but not lactose
Salmonella produces H2S gas that reacts with ferrous sulfate to produce the black-colored ferrous sulfide

Results Interpretation

No specific information is provided on results interpretation

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Description

Learn about the isolation steps of Salmonella, including non-selective enrichment pre-enrichment. Understand the pathogenic serotypes and their importance in microbiology.