brain eating amoeba

1. BRAIN EATING
AMOEBA
NAEGLERIA

2. Naegleria fowleri
– Commonly referred to as the “brain-eating amoeba”,
– Free-living microscopic amoeba, (single-celled living organism).
– Cause a rare and devastating infection of the brain called primary
amoebic meningoencephalitis (pam).
– Commonly found in warm freshwater (Eg. Lakes, rivers, and hot
springs) and soil.
– Usually infects people when contaminated water enters the body
through the nose.

3. – It travels to the brain where it causes pam, which is usually fatal.
– In very rare instances, naegleria infections may also occur when
contaminated water from other sources (such as inadequately
chlorinated swimming pool water or heated and contaminated tap
water) enters the nose
■ Domain: Eukaryota
■ Genus: Naegleria
■ Species: N. fowleri

4. Morphology

5. 2. Amoeboflagellate
o Temporary, nonfeeding, and non
dividing stage found in culture
o As a response to a change in ph or
ion concentration of the amoeba’s
environment
o Pear shaped, flagellar apparatus at
the broader end.
o Flagellar apparatus consist of 2
terminal flagella, 2 basal bodies,
microtubules, and a single striated
rootlet or rhizoplast.
o Shows rapid forward movement or
slow spinning movement.
o Reverts to trophozoite stage with in
24 hours.

6. 3. Cyst
o Spherical and about 7–15 µm
in diameter
o smooth, and have a double –
layered cyst wall.
o Single nucleus, contractile
vacuoles, and food vacuoles.
o In the environment of the
human nasal passages it can
revert to the trophozoite
stage and become infective.

7. Culture and
laboratory
animals.
■ Trophozoites are cultured in
1. Non nutrient agar inoculated
with bacteria (E.coli or
enterobactor sp) monoxenic
culture.
2. Enriched broth such as peptone
yeast extract broth without any
added bacteria axenic culture.
3. Tissue culture:- Hela cells, MRC
human embryonic lung cells, and
monkey kidney cells.
■ Rodents, rabbits, and sheep are the
laboratory animals susceptible to
experimental N.fowleri infections.

8. Life cycle
• The life cycle can occur in a human host, or freely
in an aquatic or soil environment.
• In a warm, high nutrient, aquatic environment the
trophozoite stage predominates.
• If pH or ionic changes occur surrounding the
organism, the trophozoite can transition to the
more mobile flagellated form.
• If the environment becomes depleted of
nutrients, cold, or dry the trophozoite can encyst
to survive the unfavorable conditions.
• Cysts and trophozoites can enter the human
through nasal passages, usually related to water
activities.
• Trophozoites are infective, and their penetration
of the nasal mucosa and subsequent migration to
the brain results in PAM.

9. Pathogenesis
■ Virulence factors:
– 37-kDa protein:
■ Mucinolytic activity
■ Gene nfal, cytolytic function, located in pseudopodia & food
cups
– Cytopathic enzymes:
■ In brain tissues, N.fowleri produces food cup (amebostome) in
which enzymes such as hydrolases, phospholipases, and
lysosomal enzymes are secreted.

10. ■ N. fowleri is an amphizoic amoeba, as it can survive in a free-living state
in water, soil, or in the host, which can be the human central nervous
system (CNS).
■ Seen in healthy children and adults following recreational water
activities, including swimming, diving, and water skiing.
■ Infect the human body by entering the host through the nose when
water is splashed or forced into the nasal cavity.
■ Infectivity occurs first through attachment to the nasal mucosa,
followed by locomotion along the olfactory nerve and through the
cribriform plate (which is more porous in children and young adults) to
reach the olfactory bulbs within the CNS.

11. ■ N. fowleri enters the human body in the
trophozoite form.
■ Structures on the surface of trophozoites
known as food cups enable the organism to
ingest bacteria, fungi, and human tissue.
■ The pathogenicity of N. fowleri also
dependent upon the release of cytolytic
molecules, including acid hydrolases,
phospholipases, neuraminidases, and
phospholipolytic enzymes that play a role in
host cell and nerve destruction.
■ The combination of the pathogenicity of N.
fowleri and the intense immune response
resulting from its presence results in
significant nerve damage and subsequent
CNS tissue damage, which often result in
death.

12. Signs and symptoms
■ Severe Headaches
■ Loss of the sense of smell (Anosmia)
■ Cranial Nerve Palsy’s
■ Change in personality
■ Positive Kernigs sign
■ Blurred vision
■ Stiff neck
■ Vomiting
■ Confusion
■ Positive Brudzinskis sign

13. Primary ameobic meningoencephalitis
■ Naegleria fowleri is the agent of primary amebic meningoencephalitis, a
fulminating, rapidly fatal disease.
■ More than 150 cases of this disease have been recorded worldwide.The
disease usually affects children and young adults.
■ Incubation period:- 2 to 3 days to as long as 7 to 15 days, depending
partly on the size of the inoculum and the virulence of the strain.

14. ■ The disease appears with the sudden onset of bifrontal or bitemporal
headache, fever, nausea, vomiting, stiff neck, mental status change,
and seizures. Symptoms progress rapidly to lethargy, confusion, and
coma.
■ In all of the recorded cases, the patient died within 48 to 72 hours.

15. Lab diagnosis
CSF
■ Microscopic examination of fresh, unfrozen, unrefrigerated cerebrospinal
fluid (CSF)
– (samples cannot be frozen or refrigerated because cold temperatures kill
the amebae).
■ A wet mount :- actively moving trophozoites.
■ Identified in CSF smears or cultures using hematoxylin and eosin (H&E),
periodic acid-Schiff (PAS), trichrome, Giemsa, orWright-Giemsa stains.
■ Shows ameboid trophozoites with morphology typical of Naegleria
■ A nucleus with a large, centrally located and densely staining nucleolus.

16. Tissue
■ Microscopic examination of hematoxylin and eosin (H&E), periodic acid-
Schiff (PAS), trichrome, Giemsa, orWright-Giemsa stained smears of
brain biopsy or autopsy specimens
■ Demonstrates trophozoites with morphology typical of Naegleria
fowleri.
■ The ameboid trophozoites measure 10-35 µm but when rounded are
usually 10-15 µm in diameter.The cytoplasm is granular and contains
many vacuoles.
■ The single nucleus is large and has a large, dense karyosome.
Trophozoite of Naegleria
fowleri in CSF, stained with
trichrome

17. Immunohistochemical staining
■ indirect immunofluorescent (IIF) staining and immune alkaline
phosphatase staining (IHC), use an antibody specific for Naegleria
fowleri followed by microscopic examination to identify Naegleria
fowleri in tissue, culture, or CSF
Serology
■ indirect immunofluorescent antibody (IFA) testing is currently
considered a research technique as it has not been evaluated for use as
a routine diagnostic procedure.Although IFA can be performed to
measure serum antibody titers in patient sera, most patients with PAM
die before an immune response is mounted.

18. Culture
■ It involves inoculating mammalian cell cultures and monitoring for
cytopathogenicity or growth on E. coli lawns.
■ For growing on an E. coli lawn, the sample is added to a growth plate covered
in bacteria that can serve as a food source for Naegleria fowleri.
■ Incubating the plate at a higher temperature (108°F/42°C) kills most free-
living amebae, while selecting for thermophilic amebae, such as Naegleria
fowleri .
■ This initial screen shows up as tracks made by an ameba as it moves across the
plate eating the bacteria and can be identified in cultures using hematoxylin
and eosin (H&E), periodic acid-Schiff (PAS), trichrome, Giemsa, orWright-
Giemsa stains.

19. Molecular diagnosis
■ An increasing number of PCR-based techniques (conventional and real-
time PCR) have been described for detection and identification of free-
living amebic infections

20. Treatment
■ Amphotericin B has been the traditional mainstay of PAM treatment
■ Combination therapy with multiple other antimicrobials in addition to
amphotericin, such as fluconazole, miconazole, rifampicin and
azithromycin.