L.5 Moraxella

Question 1

What type of organism is Moraxella catarrhalis?

Answer 1

Gram-negative diplococcus

Moraxella catarrhalis is known for its opportunistic pathogenicity.

Question 2

What is the primary impact of Moraxella catarrhalis?

Answer 2

Affecting the respiratory tract, especially in immunocompromised individuals.

Question 3

Where does Moraxella catarrhalis commonly colonize?

Answer 3

Upper respiratory tract, especially in children.

Question 4

What is the function of Trimeric Autotransporter Adhesins (TAAs)?

Answer 4

Mediates adhesion to host epithelial cells, critical for colonization and infection.

Question 5

Name an upper respiratory tract infection associated with Moraxella catarrhalis.

Answer 5

Otitis media (middle ear infection)

Primarily affects children.

Question 6

Which infection is more common in older children and adults associated with Moraxella catarrhalis?

Answer 6

Sinusitis.

Question 7

What is laryngitis?

Answer 7

Inflammation of the larynx, often viral but can be superinfected.

Question 8

What lower respiratory tract infections are associated with Moraxella catarrhalis?

Answer 8

Bronchitis and pneumonia.

Question 9

In which patients are bronchitis and pneumonia particularly common due to Moraxella catarrhalis?

Answer 9

Patients with Chronic Obstructive Pulmonary Disease (COPD) and those with chronic lung diseases.

Question 10

True or False: Moraxella catarrhalis may act as a superinfecting pathogen following acute viral upper respiratory infections.

Answer 10

True.

Question 11

Fill in the blank: Moraxella catarrhalis is primarily an opportunistic pathogen affecting the _______.

Answer 11

Respiratory tract.

Question 12

What is the typical appearance of Gram-negative diplococci?

Answer 12

Typically appears as Gram-negative diplococci

May appear Gram-variable due to various factors

Question 13

What causes Gram-variable appearance in Gram-negative diplococci?

Answer 13

• Resistance to decolorisation during Gram staining
• Robust outer membrane slows decolorizer penetration
• Capsule or surface proteins delay crystal violet removal
• Tightly arranged diplococci protect internal cell wall from full decolorization

These factors can affect the staining process

Question 14

What specimens are collected for laboratory diagnosis?

Answer 14

• Ear swabs/effusions
• Sputum

These specimens are crucial for accurate diagnosis

Question 15

What type of culture media is used for the organism?

Answer 15

• Nutrient agar
• Blood agar
• Chocolate agar

Blood and chocolate agar support more fastidious organisms

Question 16

Does the organism require CO₂ for growth?

Answer 16

No

This organism does not require CO₂

Question 17

What are the colony characteristics observed on Day 2?

Answer 17

White, ‘pushable’ colonies (soft and moveable under gentle pressure)

Colony characteristics help in identifying the organism

Question 18

What is the result of the Gram stain test?

Answer 18

Gram-negative diplococci (may appear Gram-variable)

The Gram stain is a key diagnostic test

Question 19

What is the result of the oxidase test?

Answer 19

Positive

Indicates the presence of cytochrome c oxidase

Question 20

What is the result of the catalase test?

Answer 20

Positive

Indicates the presence of catalase enzyme

Question 21

What is the result of the KOH test?

Answer 21

Positive

This test helps differentiate between Gram-positive and Gram-negative bacteria

Question 22

What is the motility result for the organism?

Answer 22

Non-motile

Non-motility is a key characteristic for identification

Question 23

What is the oxygen requirement for the organism?

Answer 23

Obligate aerobe

Indicates that the organism requires oxygen for growth

Question 24

What are the biochemical properties of M. catarrhalis?

Answer 24

Does NOT oxidize glucose, maltose, lactose, or sucrose (non-fermenter)

M. catarrhalis is classified as a non-fermenter based on its inability to oxidize these sugars.

Question 25

Is M. catarrhalis DNase-positive or negative?

Answer 25

DNase-positive ## Footnote This characteristic helps in differentiating M. catarrhalis from other species.

Question 26

At what temperature does M. catarrhalis grow?

Answer 26

22°C ## Footnote This ability to grow at lower temperatures helps distinguish it from fastidious Neisseria spp.

Question 27

What type of agar does M. catarrhalis grow on?

Answer 27

Nutrient agar ## Footnote Nutrient agar supports the growth of M. catarrhalis and is used in laboratory settings.

Question 28

What is the confirmatory test for M. catarrhalis?

Answer 28

Tributyrin Hydrolysis (Catarrhalis Disc Test) ## Footnote This test is used to confirm the identity of M. catarrhalis based on its enzymatic activity.

Question 29

What is the principle behind the Catarrhalis Disc Test?

Answer 29

M. catarrhalis produces butyrate esterase which hydrolyzes tributyrin, releasing indoxyl that reacts with oxygen to produce a blue-green colour ## Footnote This principle is essential for interpreting the results of the test.

Question 30

What is the procedure for the Catarrhalis Disc Test?

Answer 30

Rub test colony onto catarrhalis disc and observe for blue/green colour within 2 minutes ## Footnote Quick observation is crucial for accurate results.

Question 31

What does a positive result in the Catarrhalis Disc Test indicate?

Answer 31

M. catarrhalis (blue-green colour) ## Footnote A blue-green colour confirms the presence of M. catarrhalis.

Question 32

What does a negative result in the Catarrhalis Disc Test indicate?

Answer 32

Neisseria spp. (no colour change) ## Footnote Lack of colour change suggests the absence of M. catarrhalis.