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Listeria monocytogenes
Bacillus
Zoonosis
Erysipelothrix
Listeria monocytogenes
http://textbookofbacteriology.net/Listeria.html
Listeria
1. Overview
2. Bacteriological identification
3. Sources of Listeriosis
4. Pathogenic Mechanisms
5. Treatment
Overview
• 3 categores of listeriosis
– Adult Disease
– Disease in pregnant women
– Fetal Disease
• 1 Human pathogenic species
– L. monocytogenes
L. monocytogenes
– Gram positive coccobacilli in pairs or short chains
– Facultative anaerobe
– Facultative intracellular pathogen
– Motile (end-to-end tumbling) at 250 C not at 370 C
– Weakly β-hemolytic on sheep blood agar
– Can grow and replicate at 40 C and in high salt concentration.
Sources of listeriosis
• Humans can be intestinal carriers (1-5%)
• Found in a feces of mammalian, avian, fish
and crustacean species
• Isolated from soil, silage, and other
environmental sources
• Food sources raw vegetables,
unpasteurized milk, fresh soft cheese, and
meats
• Nosocomial transmission (neonatal nurses)
Susceptible Populations
• Elderly and Immunocompromised
• Pregnant women
• Neonates
Listeriosis in the Normal Adult
Soil
Food
Ingestion
Large Intestine
Liver & Spleen
Immune Response
Small Intestine
Recovery
Listeriosis in Normal Adult
• Acute febrile gastroenteritis
• Symptoms included body aches, fever, headache,
diarrhea, and vomiting
• Illness 24 h after ingestion of bacteria and usually lasts 2
days. Common symptoms include fever, watery diarrhea,
nausea, headache, and pains in joints and muscles.
• L. monocytogenes should be considered to be a possible
etiology in outbreaks of febrile gastroenteritis when
routine cultures fail to yield a pathogen.
Listeriosis
Elderly & Immuncompromised
Death
Large Intestine (gastroenteritis)
Brain
(meningitis)
Blood
Small Intestine
Liver & Spleen
Listeriosis in the fetus
Abortion
Sepsis at birth
Mother
Granulomatosis infantiseptica
Fetus
Placenta
Liver & Spleen
Blood
Ingestion
Small Intestine
Clinical Case
A 38-year-old woman was at her 31st week of gestation.
Fever and chills for 3 days.
No history of respiratory, urinary or gastrointestinal tract infection.
Chills and general malaise 3 days prior to this admission. Decreased fetal movement
and fetal tachycardia were noted.
On admission, leukocytosis.
Rupture of membrane with meconium stain 12 h after admission.
14 hours after admission, the fetal heart rate suddenly decelerated. Decreased fetal
movement was also noted.
A male infant in fetal distress was delivered by caesarean section 15 h after
admission.
Infant was transferred to the neonatal ICU for possible neonatal sepsis.
Seizure developed. Cerebrospinal fluid (CSF) was yellow and turbid.
Treatment of neonatal meningitis. Blood cultures and CSF culture yielded the same
organism.
Listeriosis in the Neonate
5 days – 3 weeks
post delivery
Purulent meningitis OR
Meningo-encephalitis with sepsis
< 5 days
post delivery
Sepsis
Meningitis
early onset
Mother
late onset
Ingestion
Neonate
Small Intestine
Large Intestine
Pathogenesis
• Internalins
– InlA is responsible for uptake into epithelial cells
and is required for crossing the intestinal barrier
– InlB mediates entry into a variety of cell types but
does not contribute to crossing of the intestinal cell
barrier
– Both InlA and InlB are needed for traversal of the
fetoplacental barrier
InlA signaling pathway
Listeria
InlA
E-cadherin
Plasma Membrane
catenins
β
α
InlB signaling pathway
Pathogenesis
• Phagolysosome - low pH activates exotoxin
• β-hemolysin (listeriolysin O- exotoxin)
– Cholesterol-dependent cytolysin
– Forms a pore in the phagolysosome
– Only present in virulent strain
Pathogenesis
• Phospholipase C (2 types)
• Phosphatidylinositol-specific phospholipase C
• Phosphatidylcholine phospholipase C- broad-range
phospholipase
• Both enzymes act in synergy with listeriolysin O to lyse
the phagolysosome.
Cell-cell transmission
Entry
Bacteria
Internalins
phagolysosome
Fusion
with
another
cell
Escape
1. listeriolysin O
2. Phosphatidylinositolspecific phospholipase C
replication
actin tail
Movement through cell
Extrusion via
filopods
Treatment
• Penicillin or ampicillin alone or in
combination with gentamicin
Overview
•
Infection is occupationally related
–
–
–
Fishermen
Butcher
Veterinarians
•
Contact with animals, their products or
wastes
•
Three types of human infection:
• Localized cutaneous
• Generalized cutaneous
• Septicemic which is associated with endocarditis
Bacteriological identification
•
Gram positive
•
Microaerophillic bacillus
•
Thin, pleomorphic
•
Non-motile
•
Non-encapsulated
•
Non-sporulating
Morphology/Physiology
•
Grows well on most laboratory
media.
•
After 48 hours colonies are small to
pinpoint.
•
Colonies are non-pigmented and
transparent.
•
The α-hemolysis will develop after
two days
Sources of Erysipeloid
•
Acquired through skin abrasions
•
Inflammatory violaceous lesion at the
infection site (usually fingers or hand)
•
Lesion is pruritic and painful
•
Lesion is non-supporative
Pathogenic Mechanisms
• Hyaluronidase
• Neuraminidase
Diagnosis and treatment
•
Diagnosis
• History
• Culture
•
Treatment
• Penicillin
• Resistant to vacomycin
Bacillus anthracis: Overview
CDC
A photomicrograph of Bacillus anthracis bacteria using Gram stain technique.
Anthrax : Overview
• Gram-positive rods which form spores.
• Transmission by contact with infected animals or
contaminated animal products.
• Primarily disease of cattle, sheep and goats.
• No person-to-person transmission of inhalation
anthrax.
Anthrax : Overview
• 3 distinct clinical presentations
– Cutaneous
– Gastrointestinal
– Pulmonary
Bacterial identification of
B. anthracis
Culture Characteristics
• Incubated at 35-37o C
• Cultures examined within 18-24 hours of
incubation
• Growth may be observed as early as 8 hours
after inoculation.
• Grows well on Sheep Blood Agar, but does not
grow on MacConkey agar.
Colony Characteristics
• At 15-24 hours well
isolated colonies are 2 - 5
mm.
• Non-hemolytic, nonpigmented.
Sheep blood agar plate culture of
Bacillus anthracis and Bacillus cereus.
CDC/Dr. James Feeley
In contrast to colonies of B. cereus and B. thuringiensis, colonies of
B. anthracis are not β-hemolytic.
Microscopic Characteristics
• Vegetative cells are in short chains of 2-4 cells that
are encapsulated.
• Large gram-positive rod
• The capsule can be visualized microscopically using
India Ink.
• Spores are not generally present in clinical material;
CO2 levels within the body inhibit sporulation.
• Spores may be seen in material from wound eschars,
but would not be seen in body fluids.
India Ink Staining of Clinical Samples
(Blood and CSF) for Capsule
• India ink for visualization
of encapsulated B.
anthracis in clinical
samples.
• The capsule will appear as
a well-defined clear zone
around the cells for the
positive control.
CDC/Courtesy of Larry Stauffer,
Oregon State Public Health Laboratory
Isolation From Clinical Specimens
• Blood specimens
– There may be enough organisms in the blood to see
them on direct smears by gram stain.
– B. anthracis appears as short chains of 2-4 cells
which maybe encapsulated.
• Swab specimens for cutaneous Anthrax.
• Sputum specimens
• CSF specimens.
Pathogenic Mechanisms
• Exotoxins
– plasmid-encoded (pXO1)
– 3 components
• Protective Antigen
• Edema Factor
• Lethal Factor
• Capsule
– Plasmid encoded (pXO2)
– Poly D-glutamic acid
Exotoxins
• Protective antigen
– Forms a pore in the endosome allowing EF and LF to
enter the cytosol of the cell.
• Edema Factor
– calmodulin-dependent adenylate cyclase
• Lethal factor
– a zinc-dependent endopeptidase specific for mitogenactivated protein kinase kinase (MAPKK)
Clinical Anthrax
• Cutaneous
• Gastrointestinal
• Inhalational
Cutaneous
• Most common form (95%)
• Inoculation of spores under skin
• Incubation: hours to 7 days
• Small, itchy, raised area on the skin  ulcer
surrounded by blister like lesions (24-28h)
• Blister ruptures to form a painless ulcer (eschar) with
a characteristic black necrotic center
• Profound edema around lesions
• Death 20% untreated; rare if treated
Cutaneous Anthrax
Day 5
Cutaneous Anthrax
CDC:27 year old white female with
cutaneous anthrax on right forearm
Cutaneous Anthrax
Day 7
Cutaneous Anthrax
Day 12
Gastrointestinal
• Ingestion of contaminated meat
• Incubation: hours or up to 7 days
• Fever, acute gastroenteritis, vomiting blood,
bloody diarrhea
• Mortality rate 25 -60%
Gastrointestinal anthrax
CDC: Intestinal lesion
of GI anthrax
Inhalational
• Inhalation of spores
• Most likely form of bioterrorist attack.
• Incubation: 1 to 6 days, but can be as long as 43
days.
• Gram stain of the blood and blood culture, but
not until late in the course of the illness.
• Only vegetative encapsulated bacilli are present
during infection, spores are not found in the
blood.
Inhalational
• Gradual onset (1-6 days)
– fever, non-productive cough, muscle pain, malaise
• Short period of improvement
• Abrupt development of severe respiratory distress
– dyspnea
– diaphoresis
– stridor
– cyanosis
– Shock and death usually occur within 24-36 h after the
onset of respiratory distress
• Mortality rate ~100% despite aggressive treatment
Anthrax Treatment
• Most B. anthracis strains are sensitive to a broad
range of antibiotics.
– Penicillin, ciprofloxacin, or doxycycline
• Treatment should be initiated early.
Post-Exposure Treatment
• Start oral antibiotics as soon as possible.
• Antibiotics for 60 days.
Anthrax: Vaccine
• Current U.S. vaccine (FDA Licensed)
– FDA approved for persons 18-65 year of age
– 93% protective against cutaneous and may also be
protective against inhalation anthrax.
– FDA approved for 6 dose regimen over 18 months with
yearly boosters
– 3 dose regimen (0, 2, and 4 weeks) may be effective for
post-exposure treatment
Anthrax: Vaccine
– The vaccine is a cell-free filtrate that contains
protective antigen and alum.
– Pregnant women should not be vaccinated.
– Limited availability