Listeria, Erysipelothrix

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Listeria, Erysipelothrix
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Listeria

• Classification only one species of clinical
  significance L. monocytogenes
• Morphology and general characteristics
• Small GB which may appear pleomorphic
• Nonsporing
• Motile by peritrichous flagella at RT (umbrella
  motility) and polar flagella at 370 C.

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Listeria Gram stain
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Listeria umbrella motility at RT
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Listeria

• Grows well on ordinary lab media.
• On CBA it produces beta hemolysis and colonies
  resemble Strep. pyogenes colonies
• Aerobic to microaerophilic
• Biochemistry
• Catalase
• TSI A/A, H2S-
• Esculin hydrolysis

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Listeria on CBA
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Listeria

• CAMP
• Grows in 6.5 NaCl
• 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

• Virulence factors
• Monocytosis producing agent is a lipid released
  by mechanical disruption of the cells.
• 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

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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)

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Listeria and actin polymerization
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Listeria

• LPS-like substance causes a high fever in the
  host
• Has a tropism for the CNS

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Listeria invasion
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Listeria

• Clinical significance
• In adults disease is usually mild with flu-like
  symptoms or GI distress.
• Listeriosis
• 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.

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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

• 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.

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Erysipelothrix

• Classification one species E. rhusiopathiae
• Morphology and cultural characteristics
• Pleomorphic, small GB
• Nonsporing and is related to Listeria
• Growth on CBA produces alpha or gamma
  hemolysis. May form two types of colonies
• 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

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Erysipelothrix
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Erysipelothrix
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Erysipelothrix

• Biochemistry
• Catalase
• Nonmotile
• Esculin hydrolysis
• TSIA/A, H2S
• Virulence factors
• Adherence to heart valves
• Neuraminidase
• Hyaluronidase

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Erysipelothrix

• Clinical significance
• Primarily a pathogen of swine, turkeys, and fresh
  water fish.
• 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.
• It is an occupation associated disease in which
  a reddish-blue, edematous lesion at the site of
  inoculation, primarily following trauma to the
  hands.
• Occasionally the organism disseminates to cause
  septicemia, endocarditis, and arthritis.

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Erysipeloid
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Erysipelothrix

• Antimicrobial susceptibility
• Penicillin, tetracycline or erythromycin can be
  used