02b: H. influenzae and L. monocytogenes

Question 1

H. influenzae is gram (pos/neg) (cocci/bacilli) that are (encapsulated/non-encapsulated)
(aerobes/anaerobes).

Answer 1

Gram-neg;
Coccobacilli (rods);
Both encapsulated and non-encapsulated strains exist;
Facultative anaerobes

Question 2

Which special factors must be considered for lab growth of H. flu?

Answer 2

Blood-loving; requires media (chocolate agar) supplemented with growth factors (X and V) present in blood

Question 3

T/F: H. flu (encapsulated) is member of normal flora.

Answer 3

False - but can be carried asymptomatically

Question 4

Transmission of H. flu is via:

Answer 4

Direct contact with resp droplets;

Question 5

Which specific member of H. flu is the most common cause of invasive disease?

Answer 5

Hib (H. flu type b)

Question 6

List the group of patients MOST at risk for disease from H. flu type b (aside from direct contacts of infected people).

Answer 6

Unimmunized children under 4 y.o.

Question 7

List the major risk factors for acquiring H. flu (aside from unvaccinated patients).

Answer 7

1. Sickle cell
2. Asplenia
3. HIV/immunodeficiency
4. Radiation therapy (cancer) pts

Question 8

List the virulence factors present in both encapsulated and non-encapsulated strains of H. flu. What’s the function of each?

Answer 8

1. Adhesins (attachment)
2. LPS (endotoxin)
3. O.M. proteins (attachment/colonization)
4. IgA Protease (degrades IgA)

Question 9

T/F: Both encapsulated and non-encapsulated strains of H. flu have the ability to survive within respiratory epithelial cells.

Answer 9

True

Question 10

List the virulence factors present only in encapsulated H. flu.

Answer 10

PRP (polysacc. capsule; anti-phagocytic)

*Major determinant of virulence

Question 11

T/F: Maternal Ab protect newborns against non-encapsulated H. flu, but not against encapsulated H. flu.

Answer 11

False! Ab against Hib (directed against PRP capsule)

Question 12

Most common diseases caused by non-encapsulated H. flu.

Answer 12

1. Otitis media
2. Bronchitis
3. Sinusitis

Question 13

Most common diseases caused by encapsulated H. flu.

Answer 13

1. Meningitis
2. Epiglottitis
3. Pneumonia
4. Bacteremia
5. Septic arthritis

Question 14

Lab antigen detection of H. flu (type b) is done via (X) test using (Y) particles.

Answer 14

X = agglutination
Y = PRP Ab-coated latex

Question 15

Treatment for H. flu

Answer 15

1. Beta-lactams

2. Second or third gen cephalosporins

Question 16

L. monocytogenes is gram (pos/neg) (cocci/bacilli) that are (motile/non-motile)
(aerobes/anaerobes).

Answer 16

G-pos;
Coccobacilli (rods);
Motile (at room T) with tumbling movement;
Facultative anaerobe

Question 17

T/F: L. monocytogenes can survive at 4oC in your fridge, but not at -20oC in your freezer.

Answer 17

False - can survive in both

Question 18

T/F: L. monocytogenes is an obligate intracellular pathogen.

Answer 18

False - facultative intracellular pathogen

Question 19

T/F: Colonization of humans by L. monocytogenes is common.

Answer 19

True (transient colonization) - in GI of 1-5% of people

Question 20

List the populations at high-risk of serious disease from L. monocytogenes.

Answer 20

1. Neonates/preg women
2. Elderly
3. Pt with cell-mediated immunodeficiency
4. Cancer pt
5. Diabetes/alcoholism
6. Liver/kidney disease

Question 21

How is L. monocytogenes transmitted?

Answer 21

Via ingestion (of contaminated food)

Question 22

The main virulence factor of L. monocytogenes is (X). What’s its function?

Answer 22

X = Listeriolysin O (pore-forming toxin)

Suppresses T-cell activation and impairs host immune response

Question 23

(X) bacteria replicates intracellularly by expressing ActA protein, forming (Y), and propelling itself into an adjacent cell. How does this movement contribute to bacteria’s virulence?

Answer 23

X = L. monocytogenes
Y = actin

Evade humoral immune response

Question 24

Pregnant woman with non-specific flu-like illness or fever of unknown origin should be screened for (X) infection. What are the major risks of having this infection in a pregnant woman?

Answer 24

X = L. monocytogenes

1. Increased risk of meningitis
2. Risk of fetal death, premature birth, or infection (meningitis/meningoencephalitis)

Question 25

Definitive diagnosis of L. monocytogenes requires:

Answer 25

Specific biochemical/serological tests

Question 26

Treatment of L. monocytogenes.

Answer 26

Ampicillin or penicillin G

Question 27

T/F: Antibiotic resistance of L. monocytogenes is rare.

Answer 27

True