02b: H. influenzae and L. monocytogenes Flashcards
H. influenzae is gram (pos/neg) (cocci/bacilli) that are (encapsulated/non-encapsulated)
(aerobes/anaerobes).
Gram-neg;
Coccobacilli (rods);
Both encapsulated and non-encapsulated strains exist;
Facultative anaerobes
Which special factors must be considered for lab growth of H. flu?
Blood-loving; requires media (chocolate agar) supplemented with growth factors (X and V) present in blood
T/F: H. flu (encapsulated) is member of normal flora.
False - but can be carried asymptomatically
Transmission of H. flu is via:
Direct contact with resp droplets;
Which specific member of H. flu is the most common cause of invasive disease?
Hib (H. flu type b)
List the group of patients MOST at risk for disease from H. flu type b (aside from direct contacts of infected people).
Unimmunized children under 4 y.o.
List the major risk factors for acquiring H. flu (aside from unvaccinated patients).
- Sickle cell
- Asplenia
- HIV/immunodeficiency
- Radiation therapy (cancer) pts
List the virulence factors present in both encapsulated and non-encapsulated strains of H. flu. What’s the function of each?
- Adhesins (attachment)
- LPS (endotoxin)
- O.M. proteins (attachment/colonization)
- IgA Protease (degrades IgA)
T/F: Both encapsulated and non-encapsulated strains of H. flu have the ability to survive within respiratory epithelial cells.
True
List the virulence factors present only in encapsulated H. flu.
PRP (polysacc. capsule; anti-phagocytic)
*Major determinant of virulence
T/F: Maternal Ab protect newborns against non-encapsulated H. flu, but not against encapsulated H. flu.
False! Ab against Hib (directed against PRP capsule)
Most common diseases caused by non-encapsulated H. flu.
- Otitis media
- Bronchitis
- Sinusitis
Most common diseases caused by encapsulated H. flu.
- Meningitis
- Epiglottitis
- Pneumonia
- Bacteremia
- Septic arthritis
Lab antigen detection of H. flu (type b) is done via (X) test using (Y) particles.
X = agglutination Y = PRP Ab-coated latex
Treatment for H. flu
- Beta-lactams
2. Second or third gen cephalosporins
L. monocytogenes is gram (pos/neg) (cocci/bacilli) that are (motile/non-motile)
(aerobes/anaerobes).
G-pos;
Coccobacilli (rods);
Motile (at room T) with tumbling movement;
Facultative anaerobe
T/F: L. monocytogenes can survive at 4oC in your fridge, but not at -20oC in your freezer.
False - can survive in both
T/F: L. monocytogenes is an obligate intracellular pathogen.
False - facultative intracellular pathogen
T/F: Colonization of humans by L. monocytogenes is common.
True (transient colonization) - in GI of 1-5% of people
List the populations at high-risk of serious disease from L. monocytogenes.
- Neonates/preg women
- Elderly
- Pt with cell-mediated immunodeficiency
- Cancer pt
- Diabetes/alcoholism
- Liver/kidney disease
How is L. monocytogenes transmitted?
Via ingestion (of contaminated food)
The main virulence factor of L. monocytogenes is (X). What’s its function?
X = Listeriolysin O (pore-forming toxin)
Suppresses T-cell activation and impairs host immune response
(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?
X = L. monocytogenes Y = actin
Evade humoral immune response
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?
X = L. monocytogenes
- Increased risk of meningitis
- Risk of fetal death, premature birth, or infection (meningitis/meningoencephalitis)
Definitive diagnosis of L. monocytogenes requires:
Specific biochemical/serological tests
Treatment of L. monocytogenes.
Ampicillin or penicillin G
T/F: Antibiotic resistance of L. monocytogenes is rare.
True
