Question 1

The genus Neisseria spp. are gram-negative diplococci that are

Accepted Answer

Neisseria species are known to be both oxidase and catalase positive, which helps in their identification in laboratory settings.

Question 2

After 24 hours incubation at 35°C in CO₂, the cystine trypticase agar tubes of an oxidase-positive, gram-negative diplococcus provides the following reactions: Control tube-yellow Glucose-yellow Maltose-yellow Lactose-yellow Maltose-yellow These results

Accepted Answer

C

Question 3

The end product, indoxyl, appears blue on a paper disk. What enzyme must the organism possess to create this end product?

Accepted Answer

Butyrate esterase is the enzyme that hydrolyzes indoxyl acetate to produce indoxyl, which then oxidizes to form a blue color on a paper disk.

Question 4

Thayer-Martin is a selective medium designed to isolate

Accepted Answer

Thayer-Martin agar is a selective medium specifically designed to isolate Neisseria species, including Neisseria gonorrhoeae from normal vaginal flora and Neisseria meningitidis from normal upper respiratory flora, by inhibiting the growth of contaminating bacteria and fungi.

Question 5

A gram-negative diplococcus, isolated from a purulent inner ear exudate, that produces butyrate esterase will also produce all of the following except

Accepted Answer

The gram-negative diplococcus described is likely Moraxella catarrhalis, which is known to produce butyrate esterase, oxidase, DNase, and beta-lactamase (contributing to its resistance to penicillin antibiotics). However, it does not typically produce beta-galactosidase, an enzyme that breaks down lactose into glucose and galactose.

Question 6

To determine if an individual is a carrier of an oxidase-positive, gram-negative diplococci that is glucose and maltose positive, one should culture the

Accepted Answer

The bacteria described fits the characteristics of Neisseria meningitidis, which is commonly found in the nasopharynx of carriers. Culturing the nasopharynx is the appropriate method to determine if an individual is a carrier of this specific type of bacteria.

Question 7

The ability of an oxidase-positive, gram-negative diplococcus to grow on media at room temperature is often associated with

Accepted Answer

The answer of The ability of an oxidase-positive, gram-negative diplococcus...

Question 8

Which of the following organisms has a strict requirement for CO₂ in order to grow?

Accepted Answer

The answer of Which of the following organisms has a...

Question 9

A microbiologist arrives at the processing bench to begin her day. Someone had placed the swabs received the previous night in the refrigerator. One was a urethral swab from a 15-year-old male complaining of a penile discharge. The emergency room physician is calling for any preliminary results. Which of the following statements is not appropriate to tell the physician?

Accepted Answer

The answer of A microbiologist arrives at the processing bench...

Question 10

An oxidase-positive, gram-negative diplococcus produces the following reactions in a set of CTA carbohydrate tubes:
Control-red
Glucose-red
Maltose-red
Lactose-red
Sucrose-red
One would expect to isolate this organism in infections associated with all of the
Following body sites/specimen types except

Accepted Answer

The organism described is likely Neisseria gonorrhoeae, which is an oxidase-positive, gram-negative diplococcus that does not ferment carbohydrates (as indicated by the red color in all CTA carbohydrate tubes, including the control). Neisseria gonorrhoeae is commonly associated with infections of the mucous membranes, such as the genitourinary tract, pharynx, and conjunctiva, but it is not typically found in cerebrospinal fluid unless there is a disseminated infection, making this the least expected site among the options provided.

Question 11

Which of the following oxidase-positive, gram-negative diplococcus relies on its capsule to escape the host's immune system?

Accepted Answer

Neisseria meningitidis, an oxidase-positive, gram-negative diplococcus, relies on its capsule for immune evasion and can metabolize glucose and maltose, making option C correct.

Question 12

Which of the following patients is most likely to present with meningitis due to Neisseria meningitidis?

Accepted Answer

Neisseria meningitidis commonly affects adolescents and young adults, particularly those living in close quarters such as college dormitories, making the 19-year-old college student the most likely to present with meningitis due to this organism.

Question 13

Neisseria gonorrhoeae and N. meningitidis share all of the following characteristics except

Accepted Answer

Neisseria meningitidis can be a part of the normal flora in the nasopharynx without causing disease, thus it is not strictly a pathogen. Neisseria gonorrhoeae, on the other hand, is considered a strict pathogen as it almost always causes disease when it infects the human body. Both organisms share characteristics such as the presence of pili, the ability to disseminate, and resistance to colistin.

Question 14

Commensal Neisseria spp. are often recognized by their

Accepted Answer

Commensal Neisseria spp. are often recognized by their pigment production and sensitivity to colistin.

Question 15

Which test(s) differentiate Neisseria gonorrhoeae and N. cinerea?

Accepted Answer

The answer of Which test(s) differentiate Neisseria gonorrhoeae and N....

Question 16

To differentiate Acinetobacter spp. and Neisseria spp., one could perform a(n)

Accepted Answer

The oxidase test is used to differentiate Acinetobacter spp. (oxidase-negative) from Neisseria spp. (oxidase-positive) based on the presence of cytochrome c oxidase.

Question 17

A 30-year-old male sees his physician complaining of urinary frequency and burning. A urine and swab of penile discharge were submitted for culture and Gram stain. Review the Gram stain image of the penile discharge. What can be deduced from the penile Gram stain?
 Source: CDC and Joe Miller

Accepted Answer

The answer of A 30-year-old male sees his physician complaining...

Question 18

A rectal swab from a 58-year-old male is submitted for culture for Neisseria gonorrhoeae. A gray, opaque oxidase positive colony grew on the chocolate and Thayer-Martin agar. The gram-negative diplococcus was weak glucose positive with the CTA carbohydrate tubes. This organism should be

Accepted Answer

The answer of A rectal swab from a 58-year-old male...

Question 19

An autopsy is performed on a 19-year-old female military recruit. She was healthy 24 hours earlier. Her history was unremarkable, and her vaccinations were up to

Accepted Answer

The answer of An autopsy is performed on a 19-year-old...

Question 20

A rectal swab on a 6-year-old male reveals an oxidase-positive, gram-negative diplococcus that grows on chocolate and Thayer-Martin agars. The organism proved to be beta-galactosidase negative, gamma-glutamylaminopeptidase negative, and proline-laminopeptidase positive. Based on these results you would

Accepted Answer

The answer of A rectal swab on a 6-year-old male...

Quiz 18: Aerobic Gram-Negative Cocci