This document summarizes various amoebae including Entamoeba histolytica, Naegleria fowleri, Acanthamoeba, and Balamuthia mandrillaris. It describes their morphology, life cycles, pathogenesis, clinical manifestations, laboratory diagnosis, and treatment. The key points are that these amoebae can cause intestinal and extra-intestinal infections in humans, invading tissues via ingestion or inhalation of cysts/trophozoites from the environment. Clinical symptoms vary depending on the infected site. Laboratory diagnosis involves microscopic examination of samples and molecular methods. Treatment involves antimicrobials targeting the infective stages.

1. AMOEBAE
Dr ADIL RAZA
ASSISTANT PROFESSOR,
DEPTT OF MICROBIOLOGY,
JNMC, AMU, ALIGARH

2. • Phylum Sarcomastigophora
• Subphylum Sarcodina
• Superclass Rhizopoda
• Class Lobosea
• Orders
– Euamoebida
• Entamoeba
• Endolimax
• Iodamoeba
• Amoebida
• Acanthoamoeba
• Balamuthia
– Schizopyrenida
• Naegleria

3. • Six amoebae are commonly found in the
human oral cavity and intestine:
– E. histolytica
– E. coli
– E. gingivalis
– Endolimax nana
– Iodamoeba buetschilii

4. ENTAMOEBA HISTOLYTICA
• Geographical distribution:
– Cosmopolitan.
– in India Maharashtra, TN and Chandigarh are
regions of high prevalence.

5. • Morphology:
– Trophozoite:
• 10-60 µM,
• Cytoplasm is
divided into clear
ectoplasm and
granular
endoplasm.
• Cytoplasm is
consists of RBCs,
Leukocytes and
tissue debris.
• Trophozoites are
motile with single
pseudopodium.

6. • Cyst:
• Spherical in size
• 10-15µM in diameter
• It is surrounded by thick
chitinous wall which makes
it highly resistant to gastric
acid, adverse
environmental conditions
and chlorine
concentration.
• It starts as uninucleate
body but later nucleus
divides into two and later
four.
• Cysts are only present in
the lumen of colon and in
the formed stool.

7. Entamoeba histolytica Cysts

8. • INFECTIVE STAGE: Cyst
• Cysts remain viable in moist environment for 1
month.
• Incubation period is 1-4 wks.
Entamoeba histolytica Life Cycle

9. Entamoeba histolytica Life Cycle
• CYST: ingested with
fecal contaminated
food or water.
• Excystation occurs in
the small intestine in
an alkaline
environment.
• Metacystic amebas
emerge, divide and
move down into the
large intestine.

10. INTESTINAL AMOEBIASIS
• Trophozoites colonize the
large intestine and invade
the mucosa.
• They live within the crypts
and mucosa of the large
intestinal lining.
• Trophozoites may live and
multiply indefinitely
within the crypts of the
Large intestine mucosa
feeding on starches and
mucous secretions.

11. • Cysts form in
response to
unfavorable
(deteriorating)
environmental
conditions, as they
move down the
Large intestine.
• They are released in
formed feces.

12. Entamoeba histolytica Pathology
Flask Shaped UlcersA primary ulcer can cause
rupturing of the bowel and can
cause Peritonitis.

13. EXTRA INTESTINAL AMOEBIASIS
 About 5 %
individuals with
intestinal
amoebiasis , 1-3
months after the
disappearence of
dysentry develop
hepatic amoebiasis.
A. Hepatic Amebiasis
B. Pulmonary
Amebiasis
C. Cerebral Amebiasis

14.  The centre of the
amoebic liver abscess
contains a viscous red-
brown (anchovy sauce)
or grey yellow fluid
consisting of cytolysed
liver cells, RBCs and
leukocytes.

15. LABORATORY DIAGNOSIS
Intestinal amoebiasis
• Stool examination
– gross: mucous or blood tinged semiformed/ liquid
stool.
– M/E: motile trophozoites can be seen in eosin staining.
– Cysts can be seen in iodine mount
• Blood examination
• Serology
– IHA
– IFA
– ELISA
• Culture: Diamond’s media

16. Hepatic Intestinal amoebiasis
• Diagnostic aspiration
• Liver biopsy
• Blood examination
• Stool examination
• Serological tests
– IHA (≥ 1:256), IFA(≥1:200), ELISA tests
• Molecular methods
– PCR: 16S rRNA, Prx gene …

17. TREATMENT
• Luminal amoebicides
– Diiodohydroxyquin
– Diloxanide furoate
• Amoebicides effective in the liver, intestinal wall and
other tissues.
– Emetine
• Amoebicides effective only in liver
– Chloroquine
• Amoebicides effective in both tissues and intestinal
lumen
– Metronidazole
– nitroimidazole

18. Differences between amoebic & bacillary dysentry
Character Amoebic dysentry Bacillary dysentry
Number 6-8 per day Over 10 per day
Amount Copious Small
Odour Offensive odourless
Consistensy Not adherent to container Adherent to container
RBCs In clumps Discret
Pus cells Few Numerous
Macrophages Few Numerous
Eosinophils Present Scarce
Charcot-leyden crystals Present Absent
Pyknotic bodies present Absent
Parasites Trophozoites and cyst
present
Absent
Bacteria Many motile bacteria Few or absent

19. FREE LIVING AMOEBAE
Naegleria
Acanthamoeba
Balamuthia
• They are ubiquitous in nature
• Found commonly in soil and water, where
they feed on bacteria.
• They produce diseases in CNS and eyes.

20. NAEGLERIA FOWLERI
Morphology
• Trophozoites
– Amoeboid
• Elongated, broad, actively motile
by blunt pseudopodia.
• 15-30 µM in length.
• Distinct phagocytic structure
called amoebostomes.
– Flagellate
• These are cigar shaped with two
flagella at the broader end.

21. • Cyst
– Uninucleate
– Spherical 7-15
µM and are
surrounded by a
relatively thin
cyst wall.

22. LIFE CYCLE

23. • Amoeboid form is invasive stage.
• Man acquires infection by nasal inhalation during
swimming in fresh water lakes, ponds and swimming
pools containing infective stages.
• Infection may also be acquired by inhalation of dust
containing infective forms.
• The amoeboid forms invade the nasal mucosa,
cribriform plate and travel along the olfactory nerves
to brain.
• They first invade olfactory bulbs and then spread to
the more posterior region of the brain leading to
rapidly fatal infection known as primary amoebic
encephalitis (PAM)

24. Clinical features:
• Severe frontal headache.
• Fever
• Anorexia
• Nausea and vomiting
• Signs of meningeal irritation.
• Involvement of olfactory bulbs may leads to
disturbances in smell or taste.
• Patient may develop visual disturbances,
confusion, irritability, seizure and coma.
• The disease results in death within 72 hrs of
onset of symptoms.

25. Laboratory diagnosis:
 Microscopic examination of cerebrospinal fluid
(CSF) is the method of choice for finding
amoeboid trophozoites of N. fowleri.
 Preparing and scanning saline and iodine wet
preparations of the CSF are recommended.
Samples of tissues and nasal discharge may also
be examined.
 In addition, the clinical specimens may be
cultured.
 N. fowleri amoeboid trophozoites show a
characteristic trailing effect when placed on agar
plates that have been previously inoculated with
gram negative bacilli.
TREATMENT
• Amphotericine B

26. Acanthamoeba
A. culbertsoni
A. castellani
A. hatchetti
A. polyphaga

27. MORPHOLOGY
• TROPHOZOITES
– 24-56 µM in length.
– They have irregular
appearance with
acanthopodia, tapering
spine like pseudopodia.
– has single nucleus
• CYST
– It is double walled and
therefore quite resistant
in the environment.
– 15-20 µM in size.
– No flagellate stage is
found.

29. LIFE CYCLE

30. • Man acquires infection by inhalation of
aerosol or dust containing trophozoites and
cysts.
• The trophozoites reach the lower respiratory
tract and from there they invade the CNS
through blood stream.
• The infection may also be acquired by direct
invasion through broken or ulcerated skin or
eye.

31. Clinical features:
• It causes granulomatous amoebic encephalitis (GAE).
• It occurs in persons who are immunocompromised.
• the disease is usually Of gradual onset and takes a
chronic course lasting for weeks or months.
• in healthy persons acanthamoeba causes keratitis .

32. LABORATORY DIAGNOSIS
• Demonstration of trophozoites in CSF or trophozoites
and cysts in the brain tissue.
• Demonstration of trophozoites in corneal scrappings
or trophozoites and cysts in the brain tissue.
• Wet mount of corneal scrapping shows motile
trophozoites.
• Histopathological and corneal tissues can be stained
by H&E, Giemsa, gomori’s chromium, PAS
• Serology can be done by IFAT.

33. TREATMENT
• No specific treatment for GAE.
• Total exision of the mass and treatment with
ketoconazol , penicillin and chloremphenicol
has been claimed to be useful.

34. BALAMUTHIA MANDRILLARIS
MORPHOLOGY
• TROPHOZOITE
– These are irregular in shape.
– 12-60 µM in size.
– They are sluggishly motile by finger like
pseudopodia.
• CYST
– Cysts are spherical 6-30 µM

35. • It causes CNS infection granulomatous
amoebic encephalitis (GAE), similar to that
produced by Acanthamoeba spp.
• The portal of entry is inhalation of dust or
aerosols containing trophozoites.
• Unlike Acanthamoeba it causes GAE in
immunocompetent persons, which indicates
virulent nature of this parasite.

36. Characteristics
• immunocompetent hosts usually include
young children and older individuals, although
immunocompromised hosts are more
susceptible.
• Susceptible Immunocompromised hosts,
include HIV/AIDS patients or individuals
undergoing organ transplantation or steroid
treatment, as well as drug and alcohol abusers

37. Sign and Symptoms
• Headache,
• fever,
• nausea,
• mental state abnormalities, irritability,
• hemiparesis,
• cranial nerve palsies,
• hallucinations,
• photophobia,
• sleep and speech disturbance,
• seizures

38. Laboratory diagnosis
• Wet mounts of CSF may show the presence of
amoebae;
• indirect immunofluorescence assay of tissue
sections, using anti- Balamuthia sera, is
recommended
• inoculating a portion of clinical sample on a
mammalian cell monolayer may result in the
isolation of B. mandrillaris.

39. CSF parameters:
• High protein levels,
• low glucose levels,
• amoebae rarely found in the CSF
Histopathology :
• Cysts and trophozoites found in the
perivascular spaces,
• inflammation with or without granulomas
Prognosis
• Extremely poor, with approxi 98% fatality rate