Listeria, Erysipelothrix
Listeria
Classification – only one species of
clinical significance – L. monocytogenes
 Morphology and general characteristics

Small G+B which may appear pleomorphic
 Nonsporing
 Motile by peritrichous flagella at RT
(umbrella motility) and polar flagella at 370
C.

Listeria Gram stain
Listeria umbrella motility at RT
Listeria
Grows well on ordinary lab media.
 On CBA it produces beta hemolysis and
colonies resemble Strep. pyogenes colonies
 Aerobic to microaerophilic
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Biochemistry
Catalase +
 TSI= A/A, H2S Esculin hydrolysis +

Listeria on CBA
Listeria
CAMP +
 Grows in 6.5% NaCl
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Antigenic structure
Four major serogroups (1-4) based on O
antigen
 Serotypes based on H antigen
 Type 1b accounts for most infections
although one may also find 1a and 4b in
significant amounts
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Listeria
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Virulence factors

Monocytosis producing agent – is a lipid released
by mechanical disruption of the cells.
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It causes a monocytosis to occur in the host
Internalins (InlA)– are surface associated proteins
that act to facilitate the uptake of the bacterium into
epithelial cells.
Oxygen labile hemolysin called listeriolysin (LLO)

It is a pore forming toxin that facilitates the escape of the
organism from the endosome to the cytosol
Listeria
Phospholipase – is also involved in
facilitating the escape of the organism from
the endosome to the cytosol.
 Listeric polysaccharide – is a capsule
component
 ActA – a surface protein that facilitates the
rearrangement of actin to propel the
organism through the cell and into an
adjacent cell (organism is very invasive)

Listeria and actin polymerization
Listeria
LPS-like substance – causes a high fever in
the host
 Has a tropism for the CNS

Listeria invasion
Listeria

Clinical significance


In adults – disease is usually mild with flu-like
symptoms or GI distress.
Listeriosis

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Occurs in individuals with an underlying chronic primary
disorder and is characterized by widely disseminated
abscesses and granulomas.
Lesions may be found in the liver, spleen, adrenals,
respiratory tract, CNS,and skin.
Meningitis with septicemia and pneumonia and a high
mortality rate may occur.
Listeria


Pregnancy renders an individual more susceptible
to the infection, though the effect on the mom is
usually minimal.
It can be devastating for the fetus or newborn.

In neonates, the disease occurs in two forms

Early onset – the infant is infected transplacentally with the
production of septicemia and granulomatous foci in many
organs.
This may result in abortion, stillbirth, premature delivery,
or death soon after birth.
The baby is born with cardio and respiratory distress,
vomiting, diarrhea, meningitis, hepatosplenomegaly,
and skin lesions.
The fatality rate is 70-90% in untreated cases.
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Listeria
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Late onset – the infant is infected from the genital tract
during delivery.
 Infection usually begins 1-4 weeks after birth and
is manifested as meningitis with a high fatality
rate.
Antimicrobic susceptibility/treatment
Prognosis is poor in neonates so infected moms
should be treated as soon as disease is
diagnosed
 Penicillin is the drug of choice.
 Can also use erythromycin or tetracycline.

Erysipelothrix
Classification – one species – E. rhusiopathiae
 Morphology and cultural characteristics



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Pleomorphic, small G+B
Nonsporing and is related to Listeria
Growth on CBA – produces alpha or gamma
hemolysis. May form two types of colonies

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Smooth – contains rods and coccobacilli
Rough – contains long, thin filaments
Grows on chocolate agar, but not as well as on CBA
Usually requires 48 hours for growth
Microaerophilic with better growth in CO2 or AnO2 than in
O2
Erysipelothrix
Erysipelothrix
Erysipelothrix
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Biochemistry
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Catalase –
Nonmotile
Esculin hydrolysis –
TSI=A/A, H2S+
Virulence factors
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Adherence to heart valves
Neuraminidase
Hyaluronidase
Erysipelothrix

Clinical significance

Primarily a pathogen of swine, turkeys, and fresh
water fish.

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In swine it primarily causes a cutaneous, reddish rash with
occasional complications of septicemia, endocarditis, and
arthritis.
In man, the disease called erysipeloid is the most
common form.

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It is an occupation associated disease in which a reddishblue, edematous lesion at the site of inoculation, primarily
following trauma to the hands.
Occasionally the organism disseminates to cause
septicemia, endocarditis, and arthritis.
Erysipeloid
Erysipelothrix

Antimicrobial susceptibility

Penicillin, tetracycline or erythromycin can
be used