TEST FOR GRAM-NEGATIVE COCCI (test for identifying Neisseria species)

Question 1

Differentiate Neisseria species:

Answer 1

Cystine Trypticase Agar (CTA) Sugars

Question 2

Positive result in CTA sugars:

Answer 2

Yellow color in the upper layer of the medium

Question 3

Sugars present in CTA:

Answer 3

Glucose
Maltlose
Lactose
Sucrose

mnemonic: GMLS

Question 4

CTA result:

N. gonorrhoeae
G:
M:
L:
S:

Answer 4

N. gonorrhoeae
G: (+)
M: (-)
L: (-)
S: (-)

Question 5

CTA result:

N. meningitidis
G:
M:
L:
S:

Answer 5

CTA result:

N. meningitidis
G: (+)
M: (+)
L: (-)
S: (-)

Question 6

CTA result:

N. lactamica
G:
M:
L:
S:

Answer 6

CTA result:

N. lactamica
G: (+)
M: (+)
L: (+)
S: (-)

N. lactamica is the only Neisseria spp positive for lactose

Question 7

CTA result:

N. sicca
G:
M:
L:
S:

Answer 7

CTA result:

N. sicca
G: (+)
M: (+)
L: (-)
S: (+)

N. sicca is the only Neisseria positive for sucrose

Question 8

CTA result:

N. elongate & M. catarrhalis
G:
M:
L:
S:

Answer 8

CTA result:

N. elongate & M. catarrhalis
G: (-)
M: (-)
L: (-)
S: (-)

Question 9

A test that differentiates N. elongate and M. catarrhalis is:

Answer 9

DNase test

N. elongate: DNase NEGATIVE (-)
M. catarrhalis: DNase POSITIVE (+)