2025 MLT MICROBIOLOGY ACTUAL EXAM QUESTIONS WITH
ANSWERS 2025/2026 GRADED A +
Cultures of Staphylococcus aureus supply which cultures of Haemophilus? - V factor
What organism causes whooping cough? - Bordetella pertussis
What is the preferred medium for the isolation of Bordetella pertussis? - Regan-Lowe
medium
What species of Bordetella are urease-positive and oxidase-positive? - B. parapertussis
A Brucella isolate that does not produce H2S, does not require CO2, and is not inhibited
by thionin or basic fuchsin is probably what species of Brucella? - B. melitensis
A relatively slow growing and fastidious, GNR that produces a characteristic brown
pigment on Feely-Gorman iron cysteine agar is most probably what organism? -
Legionella pneumophila
What is the BEST medium for the isolation of Legionella? - buffered charcoal yeast
extract agar
Which Gram-negative, fastidious bacillus has been isolated from air-conditioning
towers? - Legionella pheumophila
What atmospheric conditions best describe Campylobacter? - obligate microaerophilic
A curved, Gram-negative rod that is nonfermentative, nitrate positive, and
microaerophilic is probably what organism? - Campylobacter jejuni
A motile, Gram-negative, slender, curved rod that is the cause of enteritis is best
isolated on which agar? - Campylobacter blood agar
What does Campy gas mixture consist of? - 5% O2, 10% CO2, 85% N2
What organism colonizes the human stomach and is associated with peptic ulcer
disease? - Helicobacter pylori
Clue cells may be found in infections with what organism? - Gardnerella vaginalis
What kind of media extends the lag phase of normal flora and decreases the lag phase
of pathogens? - enrichment
Which type of selective media for Salmonella and Shigella uses bromthymol blue and
acid fuchsin as indicators - Hektoen enteric (HE) agar
What is the hydrogen sulfide indicator in the triple sugar iron agar? - sodium thiosulfate
, IMViC is a series of what tests? - indole, methyl red, Voges-Proskauer, citrate
What is the indicator on the methyl red test? - methyl red
Which pair of organisms can be used for quality control in the Voges-Proskauer test? -
Enterobacter (positive) and Escherichia (negative)
What is the indicator in Simmons citrate agar? - bromthymol blue
Nonfermenters produce what reaction in triple sugar iron (TSI) agar? - alkaline slant,
alkaline or neutral butt
What amino acids are used in the test for decarboxylase? - lysine, arginine, and
ornithine
How many tubes are required to perform the decarboxylase test? - 4 tubes are needed:
one for each substrate plus one control tube
What is an enzyme that removes the amino group from an amino acid? - deaminase
Organisms that produce urease do what to the medium? - hydrolyze area to ammonia
Hydrogen sulfide production, other than in triple sugar iron agar, requires a source of
metal and what other component in the test medium? - an organic source of sulfur
Which organisms are nonmotile at 37 degrees C? - Yersinia enterocolitica, Klebsiella
pneumoniae, and Shigella flexneri
Gelatinase breaks down gelatin into what end product? - amino acids
What indicates a positive DNase result after 0.1 HCl is added to the plate? - clearing
around the colony
If the negative nitrate reduction test does not change color after the powdered zine is
added, how is it reported? - positive
what is the purpose of the ONPG test? - detects slow lactose fermenters
Salmonella, Shigella, and Escherichia coli have what in common? - all are members of
Enterobacteriaceae
A Gram-negative rod isolated from a urine culture has the following reactions: IMViC
++--, Motility Pos, Urease Neg. What is the most likely ID of the organism? - E. coli
ANSWERS 2025/2026 GRADED A +
Cultures of Staphylococcus aureus supply which cultures of Haemophilus? - V factor
What organism causes whooping cough? - Bordetella pertussis
What is the preferred medium for the isolation of Bordetella pertussis? - Regan-Lowe
medium
What species of Bordetella are urease-positive and oxidase-positive? - B. parapertussis
A Brucella isolate that does not produce H2S, does not require CO2, and is not inhibited
by thionin or basic fuchsin is probably what species of Brucella? - B. melitensis
A relatively slow growing and fastidious, GNR that produces a characteristic brown
pigment on Feely-Gorman iron cysteine agar is most probably what organism? -
Legionella pneumophila
What is the BEST medium for the isolation of Legionella? - buffered charcoal yeast
extract agar
Which Gram-negative, fastidious bacillus has been isolated from air-conditioning
towers? - Legionella pheumophila
What atmospheric conditions best describe Campylobacter? - obligate microaerophilic
A curved, Gram-negative rod that is nonfermentative, nitrate positive, and
microaerophilic is probably what organism? - Campylobacter jejuni
A motile, Gram-negative, slender, curved rod that is the cause of enteritis is best
isolated on which agar? - Campylobacter blood agar
What does Campy gas mixture consist of? - 5% O2, 10% CO2, 85% N2
What organism colonizes the human stomach and is associated with peptic ulcer
disease? - Helicobacter pylori
Clue cells may be found in infections with what organism? - Gardnerella vaginalis
What kind of media extends the lag phase of normal flora and decreases the lag phase
of pathogens? - enrichment
Which type of selective media for Salmonella and Shigella uses bromthymol blue and
acid fuchsin as indicators - Hektoen enteric (HE) agar
What is the hydrogen sulfide indicator in the triple sugar iron agar? - sodium thiosulfate
, IMViC is a series of what tests? - indole, methyl red, Voges-Proskauer, citrate
What is the indicator on the methyl red test? - methyl red
Which pair of organisms can be used for quality control in the Voges-Proskauer test? -
Enterobacter (positive) and Escherichia (negative)
What is the indicator in Simmons citrate agar? - bromthymol blue
Nonfermenters produce what reaction in triple sugar iron (TSI) agar? - alkaline slant,
alkaline or neutral butt
What amino acids are used in the test for decarboxylase? - lysine, arginine, and
ornithine
How many tubes are required to perform the decarboxylase test? - 4 tubes are needed:
one for each substrate plus one control tube
What is an enzyme that removes the amino group from an amino acid? - deaminase
Organisms that produce urease do what to the medium? - hydrolyze area to ammonia
Hydrogen sulfide production, other than in triple sugar iron agar, requires a source of
metal and what other component in the test medium? - an organic source of sulfur
Which organisms are nonmotile at 37 degrees C? - Yersinia enterocolitica, Klebsiella
pneumoniae, and Shigella flexneri
Gelatinase breaks down gelatin into what end product? - amino acids
What indicates a positive DNase result after 0.1 HCl is added to the plate? - clearing
around the colony
If the negative nitrate reduction test does not change color after the powdered zine is
added, how is it reported? - positive
what is the purpose of the ONPG test? - detects slow lactose fermenters
Salmonella, Shigella, and Escherichia coli have what in common? - all are members of
Enterobacteriaceae
A Gram-negative rod isolated from a urine culture has the following reactions: IMViC
++--, Motility Pos, Urease Neg. What is the most likely ID of the organism? - E. coli
