Haemophilus Spp.

Question 1

What are the general characteristics of fastidious Gram-negative rods?

Answer 1

• Gram-negative pleomorphic coccobacilli or rods
• Nonmotile
• Aerobic or facultatively anaerobic
• Oxidase and catalase positive
• Obligate parasites of the mucous membranes

These traits are essential for identifying and understanding their pathogenicity.

Question 2

Which species of Haemophilus are major pathogenic species?

Answer 2

• H. influenzae
• H. aegyptius
• H. ducreyi

Most species of Haemophilus are nonpathogenic or produce opportunistic infections.

Question 3

What are the growth factor requirements for Haemophilus species?

Answer 3

• X factor (hemin, hematin)
• V factor (NAD)

These factors are preformed growth factors present in blood.

Question 4

What is the role of chocolate agar in the growth of Haemophilus species?

Answer 4

Chocolate agar provides both X and V factors as heat treatment of the blood inactivates the enzymes that hydrolyze the V factor.

This allows for the effective recovery of Haemophilus species.

Question 5

What is satellitism in Haemophilus species?

Answer 5

Satellitism is the phenomenon where Haemophilus species grow in proximity to other bacteria such as S. aureus, S. pneumoniae, or Neisseria on SBA.

It helps in identifying these species in clinical specimens.

Question 6

What is the significance of the capsule in H. influenzae?

Answer 6

The capsule plays the most significant role as a virulence factor, providing antiphagocytic and anticomplement capabilities.

H. influenzae type B is particularly invasive.

Question 7

What is the primary disease caused by H. ducreyi?

Answer 7

Chancroid, a sexually transmitted disease characterized by painful lesions and enlarged inguinal lymph nodes.

This organism is mostly found in developing countries.

Question 8

What specimens are collected for laboratory diagnosis of Haemophilus species?

Answer 8

• Blood
• CSF
• Middle ear exudates
• Joint fluids
• Upper and lower respiratory tract specimens
• Swabs from conjunctiva
• Vaginal swabs
• Abscess drainage specimens

Proper collection techniques are essential for accurate diagnosis.

Question 9

What is the microscopic morphology of Haemophilus species?

Answer 9

Gram-negative coccobacilli or small regular bacilli, often seen as long filaments in pure culture.

This morphology aids in identification during laboratory examinations.

Question 10

What is the colonial morphology of Haemophilus species on chocolate agar?

Answer 10

Colonies appear translucent, moist, smooth, and convex, with a ‘mousy’ or ‘bleach-like’ odor.

H. influenzae colonies are more grayish and larger if encapsulated.

Question 11

What traditional tests are used for the identification of Haemophilus isolates?

Answer 11

• Testing for growth factors (X and V factors)
• Traditional biochemicals
• Hemolysis on blood agar
• Oxidase test
• Catalase test
• Porphyrin test

These tests help differentiate between species.

Question 12

What is the porphyrin test used for?

Answer 12

To differentiate heme-producing strains of Haemophilus species.

The test eliminates the X factor requirement and provides a more straightforward identification process.

Question 13

What color do porphyrins fluoresce under UV light?

Answer 13

Reddish-orange

This fluorescence is a key characteristic used in tests for porphyrins.

Question 14

What causes the appearance of red color after the addition of KOVACS reagent?

Answer 14

Presence of porphobilinogen

Porphobilinogen is a compound that indicates certain biochemical activities.

Question 15

What does the acronym H(A)ACEK stand for?

Answer 15

Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella, Capnocytophaga

These genera are significant in human infections, particularly endocarditis.

Question 16

What type of bacteria is the HACEK group composed of?

Answer 16

Gram-negative bacilli

Their classification is important for understanding their pathogenicity.

Question 17

What is required for the growth of HACEK organisms?

Answer 17

Increased CO2 (5%-10%) environment

This is critical for culturing these organisms effectively.

Question 18

What type of infections are HACEK organisms significant for?

Answer 18

Endocarditis

They are often involved in cases of heart valve infections.

Question 19

What is the growth requirement for Aggregatibacter aphrophilus?

Answer 19

Slow growing, requiring 48 hours to grow in culture

This slow growth can complicate diagnosis.

Question 20

What is a notable feature of Aggregatibacter aphrophilus regarding its growth media?

Answer 20

Does not grow on MacConkey agar

This helps in differentiating it from other Gram-negative bacteria.

Question 21

What are the microscopic characteristics of Aggregatibacter aphrophilus?

Answer 21

Short Gram-negative bacilli; filamentous forms possible

Understanding its morphology aids in identification.

Question 22

What is the oxidase reaction of Eikenella corrodens?

Answer 22

Oxidase positive

This biochemical characteristic is crucial for identification.

Question 23

What infections is Eikenella corrodens commonly associated with?

Answer 23

• Human bites
• Clenched-fist wounds
• Periodontitis
• Osteomyelitis

These infections often arise from the organism’s normal habitat in the oral cavity.

Question 24

What is the cultural growth characteristic of Eikenella corrodens?

Answer 24

Small colonies with a distinct odor of bleach

The growth characteristics help in its identification in the lab.

Question 25

What is the most common species of Pasteurella?

Answer 25

Pasteurella multocida ## Footnote This species is frequently isolated in human infections following animal bites.

Question 26

What are the clinical manifestations of Pasteurella multocida infections?

Answer 26

* Localized infections * Respiratory tract infections * Life-threatening systemic diseases ## Footnote These manifestations highlight its pathogenic potential.

Question 27

What is a characteristic of Legionella species in terms of transmission?

Answer 27

Acquired primarily through inhalation of aerosols ## Footnote This mode of transmission is key to understanding its epidemiology.

Question 28

What are the general characteristics of Pasteurella and similar organisms?

Answer 28

Small, Gram-negative bacilli Nonmotile Oxidase positive Most will not grow on MacConkey agar ## Footnote These characteristics help in identifying and differentiating Pasteurella species in clinical settings.

Question 29

What type of infections do most Pasteurella organisms cause?

Answer 29

Opportunistic infections ## Footnote These infections usually occur following a disruption of host barriers, such as bites from cats or dogs.

Question 30

Which antibiotic are most Pasteurella organisms susceptible to?

Answer 30

Penicillin ## Footnote This susceptibility is crucial for effective treatment of infections caused by these organisms.

Question 31

What is the Gram stain appearance of Pasteurella species?

Answer 31

Exhibits short, straight bacilli with frequent bipolar staining ## Footnote This characteristic helps in the identification of Pasteurella under the microscope.

Question 32

True or False: Pasteurella species are motile.

Answer 32

False ## Footnote Pasteurella species are characterized as nonmotile.

Question 33

Fill in the blank: Pasteurella organisms are ______ positive.

Answer 33

Oxidase ## Footnote Oxidase positivity is a key biochemical characteristic used for identification.

Question 34

What are the general growth characteristics of Actinobacillus, Kingella, Cardiobacterium, Capnocytophaga, and similar organisms?

Answer 34

Grow slowly or poorly, grow in 48 hours at 35°C to 37°C, capnophilic (5% to 10% CO2), most do not grow on MacConkey agar ## Footnote Capnophilic organisms require higher carbon dioxide levels for optimal growth.

Question 35

Where are Actinobacillus, Kingella, Cardiobacterium, and Capnocytophaga typically found?

Answer 35

Normal microbiota of the nasopharynx or oral cavity ## Footnote These species are usually of low virulence.

Question 36

How do infections caused by these organisms typically occur?

Answer 36

After introduction into sterile sites via bites, droplet transmission, sharing paraphernalia, manipulations in the oral cavity ## Footnote Cardiobacterium spp. can also be found in the gastrointestinal and urogenital tracts.

Question 37

What types of infections can these organisms cause?

Answer 37

Infections vary from periodontitis to endocarditis ## Footnote Specific organisms include Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, and Kingella spp.

Question 38

What diseases are associated with Actinobacillus spp.?

Answer 38

Granulomatous disease in animals and soft-tissue infections ## Footnote Actinobacillus spp. are also known to cause infections in humans.

Question 39

What is the primary treatment for infections caused by these organisms?

Answer 39

Most infections are treated with β-lactam antibiotics ## Footnote β-Lactamase production has been found in Kingella spp.

Question 40

What is the gram-stain appearance of Actinobacillus spp.?

Answer 40

Short to very short Gram-negative bacilli ## Footnote This characteristic helps in their identification.

Question 41

What is the gram-stain appearance of Kingella spp.?

Answer 41

Short, plump Gram-negative coccobacilli with squared-off ends ## Footnote This morphology assists in their identification.

Question 42

How does Cardiobacterium hominis appear under gram-staining?

Answer 42

Pleomorphic with one rounded end and one tapered end appearing as a teardrop ## Footnote This unique shape is significant for identification.

Question 43

Describe the colonial appearance of Aggregatibacter actinomycetemcomitans.

Answer 43

Rough, sticky, adherent colonies with a greenish tinge, four- to six-pointed star-like colonies ('crossed-cigars') ## Footnote This appearance is important for laboratory identification.

Question 44

What is a notable characteristic of Kingella spp. colonies?

Answer 44

Small colonies that often pit agar ## Footnote This pitting can be a helpful diagnostic feature.