B2 G&D Lec 4: Transplacental infections Rubella virus & listeria monocytogenes Flashcards

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1
Q

What diseases are caused by Rubella virus?

A

This virus causes:

  1. Rubella
  2. Congenital rubella malformations
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2
Q

How is rubella transmitted?

A

transmitted via respiratory droplets.

• From mother to fetus transplacentally.

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3
Q

Mention the important properties of rubella virus

A
  • A member of the Togavirus family
    — Composed of single-stranded RNA, an icosahedral nucleocapsid and a lipoprotein envelope.
  • has a positive-strand RNA and therefore has no virion polymerase
  • surface spikes contain hemagglutinin.
  • single antigenic type.
  • Human is the natural host
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4
Q

Where does the Initial replication of rubella occurs?

A

in the nasopharynx and local lymph
nodes.

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5
Q

How is rubella spread?

A

via the blood to the internal organs and skin

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6
Q

What is the origin of the rubella rash?

A

The origin of the rash is unclear; it may be due to antigen antibody

mediated vasculitis

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7
Q

What is the immunity against rubella virus?

A

• Natural infection leads to lifelong immunity. Second cases of rubella do not occur.

• Antibody crosses the placenta and protects the newborn.

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8
Q

Rubella is a milder, shorter disease than ________

A

measles

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9
Q

What is the incubation period of rubella virus?

A

14 to 21 days

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10
Q

What are the clinical findings of rubella?

A
  • Brief prodromal period with fever and malaise
  • Maculopapular rash, which starts on the face and progresses downward to involve the extremities.

-Posterior auricular lymphadenopathy is characteristic.

-When rubella occurs in adults especially women, polyarthritis caused by immune complexes often occurs.

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11
Q

How long does the rubella rash lasts ?

A

Typically 3 days

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12
Q

What is the cause of Congenital Rubella Syndrome?

A

teratogen ; significance of rubella virus is not as a cause of mild childhood disease

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13
Q

When does the pregnant women get infected by rubella?

A

First trimester

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14
Q

What happens when a non-immune pregnant woman is infected by rubella early gestation?

A

significant congenital malformations can occur as a result of maternal viremia and fetal infection.

• The increased rate of abnormalities during the early weeks of pregnancy is attributed to the very sensitive organ development that occurs at that time.

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15
Q

What are the manifestations of Congenital Rubella Syndrome?

A

Some congenital shedders are asymptomatic and
without malformations

The malformations are widespread and involve primarily the heart (e.g., patent ductus arteriosus), the eyes (e.g., cataracts), and the brain (e.g., deafness and mental retardation).

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16
Q

What is considered a significant public health hazard of rubella virus in pregnant women ?

A

The infants continue to excrete rubella virus for months after
birth

Congenitally infected infants also have significant IgM titers and persistent IgG titers long after maternal antibody has disappeared.

17
Q

What are the laboratory diagnosis & findings of rubella virus?

A
  1. It can be grown in cell culture, but it produces little cytopathic effect (CPE).
  2. Serological diagnosis can also be made by:

a. Observing a fourfold or greater rise in IgG antibody titer between acute-phase and convalescent-phase sera by ELISA.

b. The presence of IgM antibody in a single acute-phase serum sample.

  1. PCR assay.
18
Q

How is rubella virus identified in pregnancy?

A

• The presence of IgM antibody indicates recent infection, whereas a 1:8 or greater titer of IgG antibody indicates immunity and consequent protection of the fetus.

• If recent infection has occurred, an amniocentesis can reveal whether there is rubella virus in the amniotic fluid, which indicates definite fetal infection.

19
Q

What does Listeria monocytogenes cause?

A

causes meningitis and sepsis in newborns, pregnant women, and immunosuppressed adults.

• It also causes outbreaks of febrile gastroenteritis.

20
Q

Mention the important properties of L. monocytogenes

A
  • small gram-positive rod arranged in V or L shaped formations similar to corynebacteria

-exhibits an unusual tumbling movement that distinguishes it from the corynebacteria, which are nonmotile

-produce a narrow zone of β-hemolysis that resembles the hemolysis of some streptococci. on blood agar

-grows well at cold temperatures

21
Q

What is the risk of listeria growing in cold temperatures?

A

The storage of contaminated food in the refrigerator can increase the risk of gastroenteritis.

22
Q

What is paradoxical growth in the cold called?

A

cold enhancement

23
Q

Who does Listeria infection transmit to?

A

(1) In the fetus or in a newborn as a result of transmission across the placenta or during delivery.

(2) In pregnant women (have reduced cell-mediated immunity) and immunosuppressed adults, especially renal transplant patients.

The organism is distributed worldwide in animals, plants and soil.

24
Q

How Listeria is transmitted orally ?

A

In humans:

  1. Primarily by ingestion of unpasteurized milk products, undercooked meat, and raw vegetables.
  2. Contact with domestic farm animals and their feces is also an important source.

• Following ingestion, the bacteria appear in the colon and then can colonize the female genital tract.

25
Q

How Listeria is transmitted to fetus ?

A
  1. From female genital tract, they can infect the fetus if membranes

rupture or infect the neonate during passage through the birth canal.

  1. Transplacental transmission
26
Q

What is the pathogenesis of Listeria invasion of cells?

A
  • mediated by internalin made by Listeria and Ecadherin on the surface of human cells.

• The ability of Listeria to pass the placenta, enter the meninges, and invade the gastrointestinal tract depends on the interaction of internalin and E-cadherin on those tissues.

27
Q

What is the pathogenesis of Listeria regarding its Survival within cells?

A

Upon entering the cell, the organism produces listeriolysin, which allows it to escape from the phagosome into the cytoplasm, thereby escaping destruction in the phagosome.

• So, Listeria preferentially grows intracellularly, cell-mediated immunity is a more important host defense than humoral immunity.

• Suppression of cell-mediated immunity predisposes to Listeria infections.

• L. monocytogenes can move from cell to cell by means of actin rockets filaments; actin polymerize and propel the bacteria through the membrane of one human cell and into another.

28
Q

What the characteristics of Gastroenteritis caused by L. monocytogenes?

A

characterized by watery diarrhea, fever, headache, myalgias, and abdominal cramps but little vomiting. Outbreaks are usually caused by contaminated dairy products.

  • Immunocompromised adults: either sepsis or meningitis
  • during pregnancy : can cause abortion, premature delivery, or sepsis
  • Newborns :

infected at the time of delivery can have acute meningitis 1 to 4 weeks later. The bacteria reach the meninges via the bloodstream (bacteremia).

29
Q

When does acute meningitis occur in newborns?

A

1 to 4 weeks

30
Q

What are the laboratory diagnosis of Listeria?

A

• Laboratory diagnosis is made primarily by Gram stain and culture.

• The appearance of gram-positive rods resembling diphtheroids and the formation of small, gray colonies with a narrow zone of βhemolysis on a blood agar plate suggest the presence of Listeria.

• The isolation of Listeria is confirmed by the presence of motile organisms, which differentiate them from the nonmotile corynebacteria.