TEXTBOOK OF DIAGNOSTIC MICROBIOLOGY
7 2026 COMPLETE EXAM PRACTICE WITH
MARK SCHEME
◉ Tapeworm proglottids. Answer: Which one of the following is
noted from a macroscopic observation?
◉ Throat swab. Answer: In which of the following specimens is a
direct microscopic examination not useful?
◉ Differential media. Answer: Chocolate agar is an example of which
of the following?
◉ MacConkey agar. Answer: Which of the following is an example of
a selective and differential medium?
◉ Urine. Answer: Which of the following specimens is cultured using
a quantitative isolation technique?
◉ Acid-fast. Answer: Which of the following stains is best used to
detect mycobacterial organisms in clinical samples?
,◉ Chitin. Answer: Calcofluor white is a colorless dye that binds with
which of the following structures?
◉ Nonviscous fluids. Answer: Cytocentrifugation is an excellent
method for which of the following types of samples?
◉ Blue. Answer: In a Wright-Giemsa-stained smear, bacteria would
appear as which of the following colors?
◉ Candida albicans. Answer: A moderate growth of a heaped, dry-
appearing, white colony is isolated from a patient with thrush. The
colony has tiny projections extending out along the edge of its
margin. A presumptive identification of this organism would be:
◉ Streptococcus agalactiae (group B). Answer: A vaginal culture
from a 25-year-old pregnant woman produced colonies on SBA and
CHOC agar, but there was no growth on MAC agar. The colonies are
described as medium size with small, diffuse zones of β-hemolysis.
This type of hemolysis is noticed when a colony is removed with a
loop. A suspected identification of this organism would be:
◉ A yeast. Answer: Medium, raised, off-white colonies with
filamentous projections are seen on SBA and CHOC agar. The
organism is likely:
, ◉ Methyl red test. Answer: Which of the following tests detects the
production of mixed acids as a result of subsequent metabolism of
pyruvate?
◉ Voges-Proskauer test. Answer: The metabolism of glucose to
pyruvate by members of the family Enterobacteriaceae is via the
Embden-Meyerhof "Parnas" (EMP) pathway. The subsequent
metabolism of pyruvate shows this reaction: Glucose → Pyruvate →
Acetylmethylcarbinol (acetoin) → 2,3-Butanediol. This reaction is
the basis for the:
◉ Glucose only. Answer: An oxidase-negative, gram-negative bacillus
that produces an acid slant and acid butt on triple sugar iron agar is
able to ferment which of the following carbohydrates?
◉ Creates an anaerobic environment. Answer: Why is an oil overlay
used when testing carbohydrate utilization?
◉ Indole. Answer: Tryptophan broth is inoculated and incubated 24
hours. After incubation, Kovac's reagent is added. A red color
develops at the surface of the broth. What product of metabolism
was formed?
◉ Decrease in pH from citrate utilization. Answer: In the citrate
utilization test, a positive result is determined by:
7 2026 COMPLETE EXAM PRACTICE WITH
MARK SCHEME
◉ Tapeworm proglottids. Answer: Which one of the following is
noted from a macroscopic observation?
◉ Throat swab. Answer: In which of the following specimens is a
direct microscopic examination not useful?
◉ Differential media. Answer: Chocolate agar is an example of which
of the following?
◉ MacConkey agar. Answer: Which of the following is an example of
a selective and differential medium?
◉ Urine. Answer: Which of the following specimens is cultured using
a quantitative isolation technique?
◉ Acid-fast. Answer: Which of the following stains is best used to
detect mycobacterial organisms in clinical samples?
,◉ Chitin. Answer: Calcofluor white is a colorless dye that binds with
which of the following structures?
◉ Nonviscous fluids. Answer: Cytocentrifugation is an excellent
method for which of the following types of samples?
◉ Blue. Answer: In a Wright-Giemsa-stained smear, bacteria would
appear as which of the following colors?
◉ Candida albicans. Answer: A moderate growth of a heaped, dry-
appearing, white colony is isolated from a patient with thrush. The
colony has tiny projections extending out along the edge of its
margin. A presumptive identification of this organism would be:
◉ Streptococcus agalactiae (group B). Answer: A vaginal culture
from a 25-year-old pregnant woman produced colonies on SBA and
CHOC agar, but there was no growth on MAC agar. The colonies are
described as medium size with small, diffuse zones of β-hemolysis.
This type of hemolysis is noticed when a colony is removed with a
loop. A suspected identification of this organism would be:
◉ A yeast. Answer: Medium, raised, off-white colonies with
filamentous projections are seen on SBA and CHOC agar. The
organism is likely:
, ◉ Methyl red test. Answer: Which of the following tests detects the
production of mixed acids as a result of subsequent metabolism of
pyruvate?
◉ Voges-Proskauer test. Answer: The metabolism of glucose to
pyruvate by members of the family Enterobacteriaceae is via the
Embden-Meyerhof "Parnas" (EMP) pathway. The subsequent
metabolism of pyruvate shows this reaction: Glucose → Pyruvate →
Acetylmethylcarbinol (acetoin) → 2,3-Butanediol. This reaction is
the basis for the:
◉ Glucose only. Answer: An oxidase-negative, gram-negative bacillus
that produces an acid slant and acid butt on triple sugar iron agar is
able to ferment which of the following carbohydrates?
◉ Creates an anaerobic environment. Answer: Why is an oil overlay
used when testing carbohydrate utilization?
◉ Indole. Answer: Tryptophan broth is inoculated and incubated 24
hours. After incubation, Kovac's reagent is added. A red color
develops at the surface of the broth. What product of metabolism
was formed?
◉ Decrease in pH from citrate utilization. Answer: In the citrate
utilization test, a positive result is determined by:
