Microbiology Lab Quiz 5

Questions and Answers

What is the purpose of an optochin susceptibility test?

Optochin susceptibility is used to differentiate Streptococcus pneumoniae from other alpha-hemolytic streptococci.

What is optochin?

Optochin is an antibiotic derived from quinine that disrupts ATP synthase activity.

How is Streptococcus pneumoniae differentiated from other streptococci in an optochin susceptibility test?

Streptococcus pneumoniae is the only streptococcus susceptible to small concentrations of optochin.

What is the optochin susceptibility test procedure?

Three or four colonies of the organism are streaked on a sheep blood agar plate and incubated at 35ºC for 24 hours. Signup and view all the answers

How does optochin inhibit growth?

Optochin diffuses through the agar and inhibits growth of susceptible organisms creating a zone of inhibition. Signup and view all the answers

How do zones of inhibition indicate susceptibility and resistance?

A zone of clearing 14 mm or greater indicates susceptibility; less than 14 mm indicates resistance. Signup and view all the answers

What is the purpose of an oxidase test?

An oxidase test is used to identify bacteria containing the respiratory enzyme cytochrome c oxidase. Signup and view all the answers

How does cytochrome c oxidase come about?

Cytochrome c oxidase is the last enzyme in the electron transport chain which transfers electrons from cytochrome c. Signup and view all the answers

How does the oxidase test test for the presence of cytochrome c oxidase?

The test identifies cytochrome c oxidase by its ability to oxidize cytochrome c and reduce a chromogenic agent. Signup and view all the answers

What are chromogenic reducing agents?

Chromogenic reducing agents are chemicals that develop color when oxidized. Signup and view all the answers

How are reducing agents added to the media?

In the oxidase test, the reducing agent is added directly to bacterial growth or onto filter paper with bacteria. Signup and view all the answers

What does the reducing agent do to the color of the medium?

A color change occurs within seconds if the reducing agent is oxidized indicating cytochrome c oxidase is present. Signup and view all the answers

What is the purpose of the EnteroPluri-Test?

The EnteroPluri-Test is a multiple test system used for rapid identification of Enterobacteriaceae and other gram-negative bacteria. Signup and view all the answers

What does the EnteroPluri-Test identify enteric bacteria based on?

The EnteroPluri-Test identifies enteric bacteria based on 13-15 different tests. Signup and view all the answers

What is used to perform an EnteroPluri-Test?

The EnteroPluri-Test consists of a tube containing 12 individual chambers capable of performing 15 tests. Signup and view all the answers

How do you perform an EnteroPluri-Test?

Touch one end of the wire to a colony and draw it back through the tube, then incubate for 18-24 hours. Signup and view all the answers

How are the results of an EnteroPluri-Test read?

Results can be read as a simple color change, recorded on a data chart for identification. Signup and view all the answers

Study Notes

Optochin Susceptibility Test

Differentiates Streptococcus pneumoniae from other alpha-hemolytic streptococci.
Utilizes optochin, an antibiotic from quinine that obstructs ATP synthase activity.
Streptococcus pneumoniae is susceptible to low concentrations (5 µg) of optochin, while others are resistant.
Procedure involves streaking colonies on sheep blood agar and placing an optochin disk, incubated in 5%-7% CO2 at 35ºC for 24 hours.
The presence of a zone of inhibition (≥14 mm) indicates susceptibility, while a smaller zone indicates resistance.

Oxidase Test

Detects bacteria with cytochrome c oxidase, integral to the electron transport chain.
Cytochrome c oxidase transfers electrons from cytochrome c, playing a crucial role in cellular respiration.
The test uses tetraethyl-p-phenylenediamine as a chromogenic reducing agent that turns purple or blue when oxidized.
Results are obtained by applying the reducing agent to the bacterial growth, with immediate color change indicating the presence of cytochrome c oxidase.

EnteroPluri-Test

A rapid multiple test system designed for identifying Enterobacteriaceae and other gram-negative, oxidase-negative bacteria.
Comprises a tube with 12 chambers capable of conducting 15 tests, utilizing a removable wire for inoculation.
Conducted by contacting a wire to an isolated colony and inoculating each chamber, followed by incubation for 18-24 hours.
Results are visualized via color change, recorded on a chart, and converted into a five-digit numeric code for identification using the EnteroPluri-Test codebook.

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Test your understanding of essential microbiology concepts related to the optochin susceptibility test, oxidase test, and EnteroPluri-Test. This quiz features flashcards that delve into the specifics of these tests and their applications in identifying bacterial pathogens.