Microbiology Lecture 4.32: Listeria monocytogenes

Is L. monocytogenes the only Listeria species that causes disease in humans?

Yes

Is L. monocytogenes motile?

Yes

When does L. monocytogenes produce flagella?

Room temperature inside host

Can L. monocytogenes grow over a broad temperature range?

Yes

Does L. monocytogenes grow in low or high salt concentrations?

High

Where is L. monocytogenes found?

1. Soil

2. Water

3. Vegetation

4. Feces

What are the high risk populations for L. monocytogenes infections?

1. Neonates

2. Pregnant women

3. Elderly

4. Immunocompromised

What is L. monocytogenes infection generally associated with?

Consumption of contaminated food

Can transplacental spread occur for L. monocytogenes?

Yes

Can L. monocytogenes tolerate a wide pH range?

Yes

Can L. monocytogenes grow in cold temperatures?

Yes

In what ways are food prepared that causes L. monocytogenes infections?

Raw or undercooked

What are the virulence factors of L. monocytogenes?

1. Phospholipases

2. Listeriolysin O

3. ActA

What is the function of Phospholipases and Listeriolysin O?

Release bacteria from phagosome into host cytosol

What does L. monocytogenes trigger?

Actin polymerization

What does actin polymerization do for L. monocytogenes bacteria?

Propel bacteria through host cytoplasm and adjacent cells

What is critical for clearance of L. monocytogenes?

Cell-mediated immunity

Where do L. monocytogenes replicate in host cells?

Cytosol

What does L. monocytogenes bacteria create due to ActA that pushes it through the host plasma membrane to the next cell?

Polymerizing Actin Tail

Does humoral immunity have a lot of effect on clearance of L. monocytogenes?

No

Is L. monocytogenes primarily intra or extracellular?

Intracellular

What is the main disease caused by L. monocytogenes?

Neonatal Disease

How is early onset neonatal disease acquired for L. monocytogenes?

Transplacentally

What is early onset neonatal disease characterized by for L. monocytogenes?

Disseminated abscesses and granulomas in multiple organs

When is late onset neonatal disease acquired for L. monocytogenes?

Shortly after birth

What is late onset neonatal disease presented as for L. monocytogenes?

1. Meningitis

2. Meningoencephalitis with septicemia

What are the diseases caused by L. monocytogenes in immunocompromised patients?

1. Bacteremia

2. Disseminated disease and meningitis

What should high risk individuals for L. monocytogenes avoid?

1. Raw/undercooked animal products

2. Soft cheeses

3. Unwashed raw vegetables