All of the following are components of triple sugar in agar, EXCEPT:

Appeared in: DSSSB 13 August 2024

Explanation

Fructose is not one of the three sugars included in the formulation of Triple Sugar Iron (TSI) agar.
TSI agar is a specific differential medium used to identify and characterize Gram-negative enteric bacilli based on their fermentation patterns.
The 'triple sugars' in TSI are exclusively glucose, lactose, and sucrose, which allow for the differentiation of bacteria that ferment glucose only, from those that can also ferment lactose and/or sucrose.

Option A: This is incorrect because Lactose is a primary component of TSI agar, present at a 1% concentration.
Option B: This is incorrect because Sucrose is also a key component of TSI agar, present at a 1% concentration.
Option C: This is incorrect because Glucose is the third sugar in TSI agar, present at a lower concentration of 0.1% to differentiate glucose-only fermenters.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Composition of Triple Sugar Iron (TSI) Agar as background academic context rather than a clinical decision trigger.
TSI agar is a fundamental tool in clinical microbiology for the presumptive identification of enteric pathogens like Salmonella, Shigella, and E. coli from clinical specimens (e.g., stool).
The distinct reaction patterns (acid/alkaline slant/butt, gas, H₂S) on TSI provide rapid, valuable clues that guide further testing and treatment decisions for gastrointestinal infections.
What if? If an organism could ferment fructose but not lactose or sucrose, it would still appear as a glucose-only fermenter (Alkaline slant/Acidic butt) on a standard TSI test, as its ability to utilize fructose would not be detected by this medium.

How to Approach the Question

First, recognize that this is a factual recall question with a negative stem ('EXCEPT'). This means you are looking for the option that does not belong.
Identify the core subject of the question, which is 'triple sugar in agar', also known as Triple Sugar Iron (TSI) agar.
Access your knowledge about the composition of common microbiological media. The name 'Triple Sugar' is a direct clue.
Mentally list the three sugars that constitute TSI agar: Glucose, Lactose, and Sucrose.
Compare your mental list with the given options.
The option that is not on your list (Fructose) is the correct answer because the question asks for the exception.

Concept Tested & Keywords

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E6 Microbiology Essentials Sastry 4e Part 1 p. 55-57

Practise the full DSSSB 13 August 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.