Gram-negative bacteria - lab algorithm

Question 0

What lab test can you use to differentiate between the Gram-negative diplococci?

Answer 0

Neisseria meningitidis ferments maltose (and glucose). Neisseria gonorrhoeae does not ferment maltose (it can only ferment glucose).

Question 1

What are the Gram-negative diplococci?

Answer 1

Neisseria meningitidis

Neisseria gonorrhoeae

Question 2

What bacteria is:
pink on Gram-stain
diplococci
maltose fermenter

Answer 2

Neisseria meningitidis

Question 3

What bacteria is:
pink on Gram stain
diplococci
does not ferment maltose

Answer 3

Neisseria gonorrhoeae

Question 4

What are 2 key lab tests to distinguish among the Gram-negative rods?

Answer 4

1) if it ferments lactose

2) if it has oxidase (among non-lactose fermenters)

Question 5

What Gram-negative rods are lactose fermenters?

Answer 5

E. coli
Klebsiella
Enterobacter
(Serratia is a slow lactose fermenter)

Question 6

Which non-lactose fermenting Gram-negative rods are oxidase positive?

Answer 6

Pseudomonas

Question 7

Which non-lactose fermenting Gram-negative rods are oxidase-negative?

Answer 7

Shigella
Salmonella
Proteus
Yersinia

Question 8

Which of the Gram-negative lactose fermenters are urease-positive?

Answer 8

Klebsiella

E. coli, Enterobacter, and Serratia are lactose fermenters that are urease-negative