GNC: Neisseria and Moraxella catarrhalis

Question 1

List the three main organisms (genus and species) which are GNC and are of clinical importance?

Answer 1

• Neisseria meningitidis
• Neisseria gonorrhoea
• Moraxella catarrhalis

Question 2

Describe the main lab. characteristics of the pathogenic Neisseria meningitidis?

Answer 2

• Usually seen intracellularly in PMN = GNIDC in CSF, blood (intracellular diplococcus)
• Grows on BA < CHOC w/ CO2
• Carbo. fermentation - Cystine Trypticase Agar (CTA)
- Glucose & Maltose Pos (Yellow)
• Oxidase +
• Catalase +

Question 3

Which species of Neisseria can grow on Thayer Martin (TM), New York City (NYC) and Gonococcal (GC) selective media and must be carefully distinguished from N. meningitidis and N. gonorrhoeae?

Answer 3

N. meningitidis, N. gonnorrhoea, N. lactamica

* N. lactamica behaves like N. meningitidis, N. gonnorrhoea but can GROW on BA & breaks down lactose

Question 4

What characteristic colony feature (x1) and biochemical tests (x2) would confirm the presence of M. catarrhalis on a BA or CHOC agar plate?

Answer 4

• Tan convex colonies (can grow on BA)
• (slides on media like hockey puck when scoop)
• TRIB + (butyrate esterase hydrolysis tributyrin)
• CTA sugars neg (Assarcharolytic)
• confirm w/ Rapid NH and API NH (biochem tests)

Question 5

What is meant by GNIDC? What presumptive organism ID and disease could you report if you identified such a feature in a smear from a urogenital site? What if you saw such a feature in blood? CSF?

Answer 5

GNIDC: Gram Neg. Intracellular Diplococci
Urogenital site: Neisseria gonorrhoea => gonorrhoea
Blood: Neisseria meningitidis => meningococcoaemia
CSF: Neiserria meningitidis => meningococcal meningitis

Question 6

What are the virulence factors of a pathogenic strain of N. meningitidis? (5)

Answer 6

• Capsule: Inhibit phagocytosis NOT ADHERENCE. => systemic infection
• Lipo-oligosaccharrides: adherance, damage PMN & tiss.
• IgA1 protease
• Pili: Attach to mucosal surfaces
• Plasmids: B-lactamase prod.

Question 7

What is meant by carrier state?

Answer 7

Host has developed humoral immunity (immune sys. dectects Ag on foreign cell)

Question 8

a) What does prophylaxis mean?

b) What two distinct methods of prophylaxis are available for N. meningitidis?

Answer 8

a) Prophylaxis: treatment given to prevent disease

b) Rifampicin & Ciprofloxin (oral) suited for not preg. & kids. Ceftriaxone (Intramuscullar) suited for kids & preg.

Question 9

What other name(s) might Moraxella catarrhalis be known as?

Answer 9

• Branhamella catarrhalis
• Neisseria catarrhalis
• Micrococcus catarrhalis

Question 10

How could you differentiate between an Acinetobacter (usually short GNB) that appears to be a GNC and the pathogenic Neisseria and Moraxella catarrhalis in this lecture?

Answer 10

Acinetobacter: GNCB (short rod), Oxidase neg, G on MAC & NLF but pale purple
Neisseria & M. catarrhalis: GNDC, Oxidase pos, NG on MAC (bc fastidious)

Question 11

Describe the main lab. characteristics of the pathogenic Neisseria gonorrhoea?

Answer 11

• GNC/GNDC/GNIDC esp. smear from urogenital site
• NG initially on BA. But grows on CHOC w/ CO2
• Carbo. fermentation - Cystine Trypticase Agar (CTA)
- Glucose Pos (Yellow)
• Oxidase +
• Catalase +

Question 12

Describe the main lab. characteristics of the pathogenic Moraxella catarrhalis?

Answer 12

• GNC - May resist decolourisaton
• Capnophilic (likes CO2)
• G on CHOC AND BA
• Assarcharolytic - can’t break down sugar i.e. gives no result
• TRIB + (butyrate esterase hydrolysis tributyrin)
• Oxidase +
• Catalase +
• Not grow on selective media: TM, GC, NYC

Question 13

What are the virulence factors of a pathogenic strain of N. gonorrhoea ?

Answer 13

• Pili: Attach to mucosal surfaces (colony type T1 & T2 piliated & virulent = sml shiny raised colonies. T3-T5 non-piliated, avirulent = lrg flat colonies
• Lipo-oligosaccharrides: adherance, damage PMN & tiss.
• IgA1 protease
• Plasmids & chrome. mediated R
• Outer membrane proteins

Question 14

Tests to confirm Neisseria sp. and Moraxella catarrhalis

Answer 14

• Neisseria sp: CTA sugar
• Moraxella catarrhalis: TRIB test
• Can confirm w/ Rapid NH and API NH (biochem tests) for most (*NH: Neisseria Haemophilus)
• Other tests: PCR

Question 15

The infections Moraxella catarrhalis causes

Answer 15

• RTI*: Otitis media; pneumonia; sinusitis
• Wound eye infections
• (rare) septicemia, meningititis, endocaditis
* opportunistic pathogen (NF of URT)

Question 16

Susceptibility testing for Moraxella catarrhalis

Answer 16

• Most strains produce B-lactamase => must test all S results with nitrocefin disk/tubes => more sensitive in detecting B-lactam enzymes (pink = pos. yellow = neg)