1. Listeria and Erysipelothrix

2. The aerobic, non-spore-forming, gram-positive rods
1) well-recognized human pathogens
(e.g., Corynebacterium diphtheriae, Mycobacterium tuberculosis),
2) others are primarily animal pathogens that can cause human disease
(e.g., Erysipelothrix rhusiopathiae, Rhodococcus equi)
3) opportunistic pathogens typically infecting hospitalized or immunocompromised patients (e.g., Corynebacterium jeikeium).
Identification of the organisms in the laboratory
Gram-positive rods that are uniform in shape include Listeria and Erysipelothrix
The coryneform rods (which include the genus Corynebacterium) comprise a large group of irregularly shaped rods
long-chain mycolic acids in their cell walls.
: acid-fast stain was developed
: Nocardia, Rhodococcus, Mycobacterium
BOX Listeria and Erysipelothrix
Organism
Historical Derivation
Listeria
Listeria, named after the English surgeon Lord Lister
L. monocytogenes
monocytum, a blood cell or monocyte; gennaio, produce (monocyte producing; membrane extracts stimulate monocyte production in rabbits, but this is not seen in human disease)
Erysipelothrix
Erythros, red; pella, skin; thrix, hair (thin, hairlike organism that produces a red or inflammatory skin lesion)
E. rhusiopathiae
rhusios, red; pathos, disease (red disease)

3. Listeria monocytogenes
History
- 1926: isolated form rabbits with mononucleosis
- 1927: given its name to honor surgeon lord Lister
- 1929: isolated from human with mononucleosis-like disease

4. Physiology and structure
- short (0.4 to 0.5 × 0.5 to 2.0 μm)
- nonbranching, gram-positive,
- facultatively anaerobic rod
- growth at a broad temperature range (1°C to 45°C) and in a high concentration of salt.
- motile at room temperature
- less so at 37°C, end-over-end tumbling motion : cold enrichment (growth 4oC)
- weak β-hemolysis when grown on sheep blood agar plates.
- bacteria are widely distributed in nature,
- human disease is uncommon and is restricted to several well-defined populations: neonates, the elderly, pregnant women, and patients with defective cellular immunity.
Gram-stain preparation showing
L. monocytogenes in cerebrospinal fluid

5. Pathogenesis and Immunity
Intracellular Growth
- can grow macrophages, epithelial cells, cultured fibriblast
- Entry : six or more leucine-rich proteins internalins (eg., InlA, InlB, InlC)
 glycoprotein receptors (host cells)
- bacterium escapes from host vacuole (phagolysosome)
: activates exotoxin (listeriolysin O), two phospholipase C
- Release into cytosol
- Rapid division
- Move to cell membrane (ActA)
becomes encapsulated
by short actin filaments
facilitates movement to periphery
with protrusion and then penetration
to neighboring cells
never exposed to humoral immunity
Avoiding antibody-mediated clearance
- β-hemolysin (listeriolysin O), phospholipase
: produced by virulent strain only
: oxygen labile
: antigenic
: disrupts phagolysosome

6. Cell-cell transmission
Entry
Internalins
Escape
Listeriolysin O
Phospholipase C
Fusion with another cell
replication
actin tail
extrusion
ActA

7. Susceptible host and source of listeriosis
Healthy children and adults
asymptomatic carriage
Pregnant women
septicemia
neonatal disease
Immunocompromized:
meningitis
Superinfections
Food products
Direct contact
Environment
Mammals
Birds
Fish
Insect

8. Clinical diseases Neonatal Disease Mother has no symptomatic illness
Two forms of neonatal disease
1) Early-onset disease (조기형 감염증)
Granulomatosis infantiseptica
- infection of fetus in utero
- can lead to abortion, disease at birth (sepsis, pneumonia, fetal distress,
seizures, rash, abscesses, and granulomas
- High mortality rate
2) Late-onset disease (지연형 감염증)
- acquired at or soon after birth
- Exposure on vaginal delivery
- can result in meningitis or meningo-encephalitis with sepsis within 2-3 weeks

9. Adult Disease - Normal adult are resistant
- Common organism in HIV infected and other immunosuppressed patients
: Gastroenteritis
: Septicemia
:Meningitis – patients with organ transplants, cancer
- pregnant women
Treatment, prevention, and control
- Penicillin or ampicillin alone or in combination with gentamicin
prevention and control are difficult : ubiquitous and most infections are sporadic
avoid eating raw or partially cooked foods of animal origin, soft cheeses, and unwashed raw vegetables.
A vaccine is not available, not evaluated prophylactic antibiotic therapy

10. Erysipelothrix rhusiopathiae
PHYSIOLOGY AND STRUCTURE
gram-positive, non-spore-forming, facultatively anaerobic rod
distributed worldwide in wild and domestic animals.
pleomorphic, with a tendency to form filaments as long as 60 μm ("hairlike")
microaerophilic, preferring a reduced oxygen atmosphere and supplemented carbon dioxide (5% to 10%).
grayish, α-hemolytic colonies on blood agar are observed after 2 to 3 days of incubation
Animal disease-particularly in swine-is widely recognized, but human disease is uncommon.
Catalase-negative, nonmotile
Produce H2S

11. Diagnosis and treatment
Erysipeloid
- Occupational disease of meat and fish handlers
- Caused by
Erysipelothrix rhusiopathiae
Diagnosis and treatment
- Diagnosis
: History and lesion
: Culture of specimen
- Treatment
: Penicillin