Transcript Human Amebic Infections

Class Lobosea &
Amebic Infections
Entamoeba histolytica
E. coli
E. gingivalis
Class Lobosea
Intestinal Amebae

Entamoeba
E. histolytica (pathogen)
 E. coli
 E. gingivalis
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Entamoeba Morphology
Ingested
RBC
Nucleus with central
karyosome and
finely divided
peripheral chromatin
Pseudopod
E. histolytica trophozoite
Entamoeba Morphology
1-4 ring-like nuclei
with finely divided
peripheral chromatin
Cyst wall and
round shape
Mature E. histolytica Cyst
Morphologic Comparison
Entamoeba histolytica
Cysts
Trophozoites
Thick wall
Plasmalemma (thin)
1-4 ring-like nuclei
1 ring-like nucleus
Chromatoidals (blunt)
Lacking
Round, 14-20 µm
Irregular, 12-17 µm
Concentratable
Labile
Life Cicle of E. histolytica
Amebiasis Transmission
 Humans acquire E. histolytica
by:
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Ingesting cysts in fecally
contaminated food or drink
Rarely by directly inoculating
trophozoites into colon or other
sites (anal sex?)
Fecal-Oral transmission (hand
to mouth)
Infective cysts and
trophozoites pass in feces
E. histolytica Stages - CYSTS
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Usual Infective Stage for humans
Resistant walls maintain viability
If moist can last several weeks
 Killed by desiccation or boiling
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Usual Diagnostic Stage in formed stools
Can be concentrated and stained easily
 Not seen in liquid (diarrheic) stools or tissues
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E. histolytica Stages - TROPHOZOITES
Are the motile, feeding stages that:
 Cause amebiasis (damage tissue)
 Spread throughout the body, but ...
 rarely transmit the infection to others
 are labile in liquid stools or tissue, and
 must be rapidly found or preserved (quick
fixation & cold storage) for laboratory diagnosis
Pathogenesis of Amebiasis
Trophozoites ...
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Attach to mucosal epithelial cells (MEC)
Lyse MEC
Ulcerate and invade mucosa
Cause dysentery (diarrhea + blood)
Metastasize via blood &/or lymph
Form abscesses in extraintestinal sites
Clinical Classification of Amebiasis
(World Health Organization)
Asymptomatic (intestinal) Amebiasis "Cyst Passers”
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Most common
Infection may continue without clinical symptoms for weeks to months ...
 May spontaneously resolve (self cure)/or carrier state
Symptomatic Infection:
Intestinal Amebiasis: (colon and rectum)
Acute Dysenteric (dysentery)
Chronic Non-Dysenteric (“self-cured”)
Extra-Intestinal Amebiasis:
Amebic Liver Abscess (ALA)
Amebic Pulmonary Abscess
Other sites (brain, skin, GU, ?)
Acute Dysenteric Amebiasis:
Amebic Dysentery
Symptoms:
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Bloody mucoid diarrhea
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RBCs and few WBCs (pus) in stools
Abdominal pain
weight loss
bloating, tenesmus and cramps
Signs:
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Fever (33%)
Diffuse abdominal tenderness
Tender (enlarged) liver
Stools positive for trophozoites +/- WBC
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NOT cysts in loose stools
Pathology
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Intestinal ulcers are due to enzymatic
degradation of tissue.
The infection may result in appendicitis,
perforation, stricture granuloma, pseudopolyps, liver abscess
Sometimes brain, lung and spleen abscesses
can also occur. Strictures and pseudo-polyps
result from the host inflammatory response.
Amebic abscess of liver
1.
2.
Gross pathology of liver containing amebic abscess
Gross pathology of amebic abscess of liver.
Chronic Non-Dysenteric Amebiasis:
“self-cured” carrier state
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37% symptomatic >5 years
Intermittent diarrhea, mucus, abdominal pain,
flatulence and/or weight loss
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E. histolytica trophs (rarely cysts) in stools
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Positive serology
Intestinal Amebiasis Complications
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Intestinal perforation and Peritonitis (a
surgical emergency)
Ameboma
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Palpable mass of granulation tissue that may
obstruct colon
Toxic megacolon
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complication of inappropriate steroid therapy
Entamoebasis
injuries of lungs
perforation of diaphragm
abscess in liver
injury of ascending colon
injury of descending colon
Extra-Intestinal Amebiasis:
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Amebic Liver Abscess (ALA)
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Symptoms
 dysentery (1 yr), weight loss, abdominal pain, chest or shoulder
pain
Complications
 Pulmonary Abscess: by direct extension through the diaphragm into
thorax
 Rupture into the pleural cavity and/or hepatobronchial fistulas =>
trophozoites in sputum!
 Extension to other sites, including
 peritoneum, pericaridum, others
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Amebic Pulmonary Abscess
Other sites: brain, skin, urogenital system
DX: Laboratory Diagnosis of
Hepatic Amebiasis
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Examine stools for trophs/cysts (suggestive)
Blood cell counts - leukocytosis?
Radiologic Studies
Serologic tests
Catheterize abscess and aspirate: Examine
"anchovy paste" aspirate for trophozoites and do serologic
testing for amebic antigens
Culture for other pathogens (sterile on first stick, then contaminants)
Chemotherapeutic Trial
Diagnosis of Intestinal Amebiasis
Techniques:
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Direct Fecal Smear (trophs and cysts)
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Fecal concentration techniques - (cysts)
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Permanent Stained Fecal Smear
Serologic Tests (for chronic disease)
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E. histolytica: Microscopy
1
2
1.
2.
Entamoeba histolytica trophozoites in section of intestine
Entamoeba histolytica cyst and trophozoite, haematoxylin stained
Entamoeba
Entamoeba
Prevention/Control of Amebiasis
Individual measures
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Diagnosis and treatment of E. histolytica patients
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no animal reservoirs (other than humans) are known
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Safe drinking water (boiling or 0.22 µm filtration)
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Cleaning of uncooked fruits and vegetables
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Prevention of contamination of food
Prevention/Control of Amebiasis
Community measures
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Public services and utilities
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Adequate disposal of human stools
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Safe and adequate water supply
Primary health care systems
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Health education (washing hands, cleaning and protecting food,
controlling insects)
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Specific surveillance programs and Control programs integrated
into ongoing sanitation & diarrhea control
Health Regulations
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Control of food vendors and food handlers
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Control of flies and cockroaches
Entamoeba coli
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food
vacuole
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nucleus
It is a commensal of the
human large intestine, but it
looks much like E. histolytica
Cyst usually has 8 nuclei
Does not produce the proteindegrading [proteolytic] enzymes
E. coli: Morphologic Comparison
Entamoeba gingivalis
Red blood
cells
amoeba
Entamoeba gingivalis
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lives in/on the teeth, gums, and sometimes
tonsils.
it measures 10-35 µm in length
is present in all cases of active periodontitis
does not produce the cysts
Infections with
Free Living Amebae
Naegleria fowleri
Acanthamoeba spp.
Diseases caused by F.L.A.
ORGANISM
DISEASE(S) CAUSED
CYSTS
TROPHOZOITES
not present in
tissues or in
humans
8-15 µm (smaller than A.
sp.) with lobate pseudopodia
Acanthamoeba sp. GAE
Granulomatous Amebic
or
Encephalitis (slower to
leptomyxid
develop)
amebae
present in
tissues; have a
wrinkled
double wall
15-25 µm (larger than Nf)
with filiform pseudopodia
Acanthamoeba sp. Keratitis
(eye infection )
ditto
ditto
Naegleria fowleri
PAM
Primary Amebic
Meningoencephalitis
(fulminant)
Free Living Amebae Not seen
in humans
Naegleria
Acanthamoeba
cysts & trophs
are seen in
humans
Life cycle of Naegleria fowleri
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1 – cyst,
2 – amoeba makes it way into cranium,
3 – switches to flagellate in order to swim into mouth or nose.
Primary Amebic Meningoencephalitis PAM
An acute suppurative infection of the brain
and meninges that is rapidly fatal and
usually not diagnosed antemortum
Caused by Naegleria spp.
 Headache, lethargy and olfactory problems
 Sore throat, runny nose, severe headache,
vomiting, stiff neck, confusion leading to ...
 Coma and death
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Primary Amebic Meningoencephalitis PAM
Thermophilic, chlorine tolerant trophozoites
penetrate cribiform plate and follow
olfactory nerves into brain ...
Acute inflammation and hemorrhagic
necrosis
 Sanguinopurulent exudate containing trophs
is found in meninges & tissues
 CSF: Glucose -, Protein +, Leukocytes +
 NEG Gram stains and bacterial CSF cultures
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Acanthamoeba spp.
Acanthamoeba
trophozoites with
acanthopodia
Acanthamoeba
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are found in the soil and dust, in fresh water (lakes,
rivers, and hot springs and in hot tubs.
may also be found in sea water
can also be found in contact lens paraphernalia
Acanthamoeba have been found in the nose and throat
of healthy people as well as those with compromised
immune systems.
Acanthamoeba
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can enter the skin through a cut, wound, or through
the nostrils
can travel to the lungs and through the bloodstream to
other parts of the body, especially the central nervous
system.
can enter the eye via contact lenses or through a
corneal cut or sore. Infection, keratitis or a corneal
ulcer results.
In addition, it can cause skin lesions and/or a systemic (whole body) infection!!!
Acanthamoeba Keratitis
Corneal infection with Acanthamoeba spp.
trophozoites & cysts
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Ulcerations & “Ring Infiltrate” of cornea
Induced by
trauma to eye, exposure to contaminated H2O
 contact lens wear with tap water rinsing
 Cavorting in hot tub wearing soft-contacts!
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Granulomatous amebic encephalitis
(GAE)
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Acanthamoeba spp. cause a serious, most often
deadly infection called GAE
Symptoms:
headaches, stiff neck, nausea and vomiting, tiredness,
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.