Naegleria Fowleri A 45-year-old man who had been feeling unwell for several months - PowerPoint Presentation

Slide1

Naegleria

Fowleri

Slide2

A 45-year-old man who had been feeling unwell for several months visited his internist complaining of

headache, dizziness, nausea, vomiting, extreme tiredness, and fever

. The patient had been taking prednisone for a relapse of chronic ulcerative colitis. Slide3

On examination, the physician noted that the patient had

nuchal rigidity and appeared confused

. He performed a lumbar puncture. CSF was sent to the laboratory for bacterial and viral cultures. The Gram stain showed

many neutrophils but no bacteria

. Slide4

Nuchal rigidity – inability to flex forward the neck musclesSlide5

To rule out amebic encephalitis, the physician asked that a wet mount be prepared from the patient

’

s CSF. Microscopic examination of this preparation revealed

motile amebic trophozoites

. Cultures were negative for bacteria and viruses. Slide6

A biopsy specimen containing the parasite causing this patient

’

s infection is shown

inSlide7
Slide8

QUESTIONS

1. Which ameba would you expect to be causing this patient

’

s infection? What is the name of this infection? Slide9

Answer

Acanthamoeba spp.

granulomatous amebic encephalitis (GAE)

Once infected, a person may suffer with headaches, stiff neck, nausea and vomiting, tiredness, confusion, lack of attention to people and surroundings, loss of balance and bodily control, seizures, and hallucinations. Signs and symptoms progresses over

several weeks

and death usually occurs.Slide10

QUESTIONS

2. Which ameba may cause a more serious and acute CNS infection and may be confused with this parasite? Slide11

Answer

Naegleria fowleri

Infection with

Naegleria

causes the disease

primary amebic meningoencephalitis (PAM)

, a brain inflammation, which leads to the destruction of brain tissue.

Initial signs and symptoms of PAM include headache, fever, nausea, vomiting, and stiff neck. As the ameba causes more extensive destruction of brain tissue this leads to confusion, lack of attention to people and surroundings, loss of balance and bodily control, seizures, hallucinations. The disease progresses rapidly and infection usually results in death within

3 to 7 days

. Slide12

QUESTIONS

3. How can you distinguish between these amebae? Slide13
Slide14
Slide15

QUESTIONS

4. How do the infections caused by these two parasites differ? Slide16
Slide17

Answer

PAM occurs in persons who are generally healthy prior to infection. Central nervous system involvement arises from organisms that penetrate the nasal passages and enter the brain through the cribriform plate. The organisms can multiply in the tissues of the central nervous system and may be isolated from spinal fluid. In untreated cases death occurs within 1 week of the onset of symptoms. Slide18
Slide19

Answer

GAE occurs in persons who are immunodeficient in some way; the organisms cause a granulomatous encephalitis that leads to death in several weeks to a year after the appearance of symptoms. The primary infection site is thought to be the lungs, and the organisms in the brain are generally associated with blood vessels, suggesting vascular dissemination. Prior to 1985 amoebae had been reported isolated from diseased eyes only rarely; cases were associated with trauma to the eye. In 1985-1986, 24 eye cases were reported to CDC and most of these occurred in wearers of contact lenses. It has been demonstrated that many of these infections resulted from the use of home-made saline solutions with the contact lenses.Slide20

QUESTIONS

5.

How is the laboratory diagnosis of this infection made? Slide21

Answer

In Naegleria infections, the diagnosis can be made by microscopic examination of

cerebrospinal fluid (CSF)

. A wet mount may detect

motile trophozoites

, and a Giemsa-stained smear will show trophozoites with typical morphology.Slide22

Answer

In Acanthamoeba infections, the diagnosis can be made from microscopic examination of stained smears of

biopsy specimens (brain tissue, skin, cornea) or of corneal scrapings

, which may detect

trophozoites and cysts

. Cultivation of the causal organism, and its identification by direct immunofluorescent antibody, may also prove useful.Slide23

QUESTIONS

6. Does the ameba causing CNS infection in this patient cause other types of infections? Slide24

Answer

Acanthamoeba

can enter the

skin

through a

cut, wound, or through the nostrils

. Once inside the body, amebas can travel to the

lungs

and through the bloodstream to other parts of the body, especially the

central nervous system (brain and spinal cord)

.Slide25

Answer

Through improper storage, handling, and disinfection of contact lenses,

Acanthamoeba

can enter the

eye

and cause keratitis resulting

in superficial

corneal abrasions.Slide26

KeratitisSlide27

QUESTIONS

7. Which other free-living ameba, recently placed in the same genus as this parasite, causes a CNS infection in humans? Slide28

Answer

Acanthamoeba culbertsoni

Acanthamoeba polyphaga



eyes infection

Acanthamoeba castellanii

Acanthamoeba palestinensis



CNS infection

Acanthamoeba astronyxis



CNS infection

Acanthamoeba hatchetti



eyes infection

Acanthamoeba rhysodesSlide29

QUESTIONS

8. Why is there no satisfactory treatment available to treat this infection? Slide30

Answer

Treatment with

sulfamethazine

may be effective in controling

Acanthamoeba spp.

The following agents have been used to successfully eliminate the amoebic infection in the eye:

ketoconazole, microconazole, and propamidine isothionate

; however,

penetrating keratoplasty

has been necessary to restore useful vision.Slide31

Keratoplasty

– surgery to the cornea

Penetrating

keratoplasty

– corneal transplant Slide32

Naegleria fowleri

Morphology , Biology and Life cycle:

flagellate form

*

Life cycle stage consist

: -motile

trophozoite

:

-

nonmotile

cysts

ameboid

form

*

Reproduction

: simple binary fission

*

Ameboid

form

:

found in tissue , forms a single pseudopod,

dimensions 7 by 20

μ

m,

With a nucleus contain a large central

karyosome

*

Flagellate form

:

with two flagella, pear-shaped, do not

divide

*

Cyst form

:

uninucleate

, circular 7-10

μ

m

in diameter, nucleus is similar to

troph

.

Slide33

Naegleria formsSlide34

Naegleria cyst & trophozoiteSlide35

Life cycle Slide36

Symptoms and pathogeesis

Primary Amebic Meningoencephalitis(P.A.M

.) :

Symptoms

;

headache, fever, nausea

and vomiting accompanied by signs

of meningitis with involvement of the

olfactory, frontal, temporal, and

cerebral areas

Death

: occurs early; the entire

clinical course seldom extends

beyond 3 to 6 days.Slide37

Acanthamoeba

( Hartmanella

) spp.

Morhology, Biology and Life cycle:

These amebae are similar in appearance to the ameboid stage of

Naegleria but have no flagellate stage.

Cyst & Trophozoite may be found in tissue, but cysts are never seen in

Naegleria

infections.

Pseudopods are acanth formsSlide38

Acanthamoeba trophozoiteSlide39

Thanks for your attention