This textbook is available atAmazon.com Logo
Microbiology: Laboratory Theory & Application, Brief 3rd Edition

Microbiology: Laboratory Theory & Application, Brief (3rd Edition)

Book Edition3rd Edition
Author(s)Leboffe, Pierce
ISBN9781617314773
PublisherMorton Publishing
SubjectBiology
Section 7-1: Snyder Test
Observations and Interpretations
Section 7-2: Antimicrobial Susceptibility Test: Disk Diffusion (Kirby-Bauer) Method
Observations and Interpretations
Section 7-3: Morbidity and Mortality Weekly Report (MMWR) Assignment
Data and Calculations

Chapter 7, Section 7-1, Observations and Interpretations, Exercise 1

Page 445

Here is a tip:

Bromcresol green is used as the pH indicator that changes to green on acid production.

Explanation

The Snyder test employs the color indicator bromocresol green, which is present in the differential medium, to detect dental caries. The treatment also includes the use of paraffin. Saliva is secreted while chewing paraffin and obtained as a sample for the Snyder test. Snyder test is performed on this sample of saliva. At pH [potential of hydrogen] 4.8, the indicator is green, and at pH 4.4, it is yellow. If the bacteria that cause dental caries is present in the saliva, the indicator turns yellow. 

 

The culture of L. delbrueckii is used as a positive control [shows the expected results], and an uninoculated culture is used as a negative control [does not show the expected results]. The test results are indicated by a change in the color of Snyder agar tubes. If the lactobacilli bacteria that causes dental caries is present in the saliva, the indicator turns yellow. For this reason, the culture of L. delbrueckii changed color within 24 hours and remained yellow after 48 and 72 hours.

Sample Response

  • Color of agar inoculated with Lactobacillus delbrueckii changed to yellow after 24 hours of incubation.
  • Color of agar inoculated with Lactobacillus delbrueckii remained yellow up to 48 hours of incubation.
  • Color of agar inoculated with Lactobacillus delbrueckii remained yellow after 72 hours of incubation.
How would you rate this answer and explanation?
Did you like this example?
Subscribe for full access
Page 445