6.5% NaCl (Salt) Broth

The video tutorial explains the 6.5% salt broth test, a simple method to determine bacterial growth in high salt concentrations. It compares this test with MSA, highlighting that while Staphylococcus can survive 7.5% salt, some Streptococcus species can survive 6.5%. The procedure involves inoculating and incubating broth, then checking for turbidity or sedimentation as growth indicators. The video details how to interpret results by comparing inoculated samples with controls, using examples to illustrate growth positive and negative outcomes. The test is primarily used to differentiate Streptococcus species.

What is the primary difference between normal TSB broth and the 6.5% salt broth?

• The type of bacteria used

• The temperature of incubation

• The incubation time

• The addition of 6.5% salt

Why can some Streptococcus species survive in 6.5% salt broth?

• They are resistant to all salt concentrations

• They have a special enzyme that neutralizes salt

• They are not affected by salt at all

• They can survive at slightly lower salt concentrations than 7.5%

What is the purpose of using a control tube in the 6.5% salt broth test?

• To ensure the broth is sterile

• To test the pH level of the broth

• To compare and identify growth patterns

• To measure the temperature of the broth

Which of the following indicates a growth positive result in the 6.5% salt broth test?

• The broth changes color

• The broth is clear and identical to the control

• The broth shows turbidity or sedimentation

• The broth has a lower pH

What does sedimentation in the broth indicate?

• Presence of bacterial growth

• No bacterial growth

• Evaporation of the broth

• Contamination of the broth

How can you confirm a growth negative result?

• By comparing it to a control and finding no difference

• By measuring the pH level

• By checking the temperature

• By observing a change in color

What is the main application of the 6.5% salt broth test?

• To identify all types of bacteria

• To test the effectiveness of antibiotics

• To differentiate Streptococcus species based on salt tolerance

• To measure the salt concentration in broth