2025 MLT MICROBIOLOGY TEST BANK EXAM QUESTIONS WITH
ANSWERS 2025/2026 GRADED A +
What differentiates Thayer-Martin medium from modified Thayer-Martin medium? -
trimethoprim lactate
What is the medium of choice for culturing gonococci and meningococci? - modified
Thayer-Martin
When performing the oxidase test, what technique CANNOT be used? - use a nichrome
loop to transfer the colony to the filter paper
What color is a positive oxidase test? - purple
What genera is not oxidase positive? - Haemophilus
Neisseria meningitidis degrades which sugars? - glucose and maltose
Why should beta-lactamase tests be performed with growth from primary isolation
media? - plasmid coding for the enzyme may be lost on subculturing
What method is NOT used for testing for the production of beta-lactamase? -
saccharogenic method
What methods are used for testing for the production of beta-lactamase? - chromogenic
cephalosporin method, acidometric method, iodometric method
What indicates a positive reaction for the beta-lactamase chromogenic cephalosporin
method? - color change
What test can give a presumptive identification of Moraxella catarrhalis if the isolate is a
Gram-negative diplococci that is oxidase positive and isolated from a body fluid from the
middle ear? - beta-lactamase test
What is the morphology of Corynebacterium diptheriae? - Gram-positive, nonmotile rods
The terms "picket fence" and "Chinese letters" describe the common arrangements of
cells for which organism? - Corynebacterium
Babes-Ernest granules are characteristic of what organism? - Corynebacterium
diphtheriae
What is the purpose of potassium tellurite in tellurite medium? - inhibits the normal flora
Potassium tellurite medium produces what color colonies of Corynebacterium
diphtheria? - gray-black
, when culturing Corynebacterium diphtheriae, what media will enhance pleomorphism
and granule production? - Loeffler serum agar
The Elek test is for the detection of which toxin? - Corynebacterium diphtheriae toxin
What diphtheroids is normal flora of the throat? - Corynebacterium
pseudodiphtheriticum
How long does the morphological cycle of Rhodococcus equi from coccoid to rod form
take? - 24 hours
What organism is a Gram-positive to Gram-variable coccobacillus? - Listeria
monocytogenes
Refrigeration of the specimen for several months may enhance months may enhance
isolation of which organism? - Listeria monocytogenes
Listeria monocytogenes produces a positive in what biochemical test? - catalase
What will differentiate Listeria monocytogenes from Corynebacteria species? -
nonmotile and salicin negative
Spore-forming cells in bamboo pole arrangement are characteristic of what organism? -
Bacillus anthracis
Which aerobic, Gram-positive, sporulating rod can cause food poisoning? - Bacillus
cereus
What stain will stain acid-fast bacilli? - Kinyoun stain
What is the function of N-acetyl-L-cysteine-NaOH? - liquefy mucus and control
contaminants
How should mycobacterial cultures be incubated? - in 5% CO2
What media is clear so that colonies of mycobacteria can be examined microscopically?
- Middlebrook 7H11
What is NOT used for the identification of mycobacteria? - spore formation
What is used for the identification of mycobacteria? - biochemical reactions, pigment
production, growth rate
What color is a negative enzymatic hydrolysis Tween 80 test? - amber
ANSWERS 2025/2026 GRADED A +
What differentiates Thayer-Martin medium from modified Thayer-Martin medium? -
trimethoprim lactate
What is the medium of choice for culturing gonococci and meningococci? - modified
Thayer-Martin
When performing the oxidase test, what technique CANNOT be used? - use a nichrome
loop to transfer the colony to the filter paper
What color is a positive oxidase test? - purple
What genera is not oxidase positive? - Haemophilus
Neisseria meningitidis degrades which sugars? - glucose and maltose
Why should beta-lactamase tests be performed with growth from primary isolation
media? - plasmid coding for the enzyme may be lost on subculturing
What method is NOT used for testing for the production of beta-lactamase? -
saccharogenic method
What methods are used for testing for the production of beta-lactamase? - chromogenic
cephalosporin method, acidometric method, iodometric method
What indicates a positive reaction for the beta-lactamase chromogenic cephalosporin
method? - color change
What test can give a presumptive identification of Moraxella catarrhalis if the isolate is a
Gram-negative diplococci that is oxidase positive and isolated from a body fluid from the
middle ear? - beta-lactamase test
What is the morphology of Corynebacterium diptheriae? - Gram-positive, nonmotile rods
The terms "picket fence" and "Chinese letters" describe the common arrangements of
cells for which organism? - Corynebacterium
Babes-Ernest granules are characteristic of what organism? - Corynebacterium
diphtheriae
What is the purpose of potassium tellurite in tellurite medium? - inhibits the normal flora
Potassium tellurite medium produces what color colonies of Corynebacterium
diphtheria? - gray-black
, when culturing Corynebacterium diphtheriae, what media will enhance pleomorphism
and granule production? - Loeffler serum agar
The Elek test is for the detection of which toxin? - Corynebacterium diphtheriae toxin
What diphtheroids is normal flora of the throat? - Corynebacterium
pseudodiphtheriticum
How long does the morphological cycle of Rhodococcus equi from coccoid to rod form
take? - 24 hours
What organism is a Gram-positive to Gram-variable coccobacillus? - Listeria
monocytogenes
Refrigeration of the specimen for several months may enhance months may enhance
isolation of which organism? - Listeria monocytogenes
Listeria monocytogenes produces a positive in what biochemical test? - catalase
What will differentiate Listeria monocytogenes from Corynebacteria species? -
nonmotile and salicin negative
Spore-forming cells in bamboo pole arrangement are characteristic of what organism? -
Bacillus anthracis
Which aerobic, Gram-positive, sporulating rod can cause food poisoning? - Bacillus
cereus
What stain will stain acid-fast bacilli? - Kinyoun stain
What is the function of N-acetyl-L-cysteine-NaOH? - liquefy mucus and control
contaminants
How should mycobacterial cultures be incubated? - in 5% CO2
What media is clear so that colonies of mycobacteria can be examined microscopically?
- Middlebrook 7H11
What is NOT used for the identification of mycobacteria? - spore formation
What is used for the identification of mycobacteria? - biochemical reactions, pigment
production, growth rate
What color is a negative enzymatic hydrolysis Tween 80 test? - amber
