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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_182_библиотеки_им_акад_М_И_Перельмана.pdf
CRYPTOSPORIDIOSIS AND OTHER COCCIDIA INFECTIONS
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Microscopic Features
(Left) Histological section of
small intestine shows mixed
inflammation with prominent
eosinophils and basophilic
spherical oocytes of coccidial
infection . (Right) In this
small bowel biopsy, areas
of the mucosa have large
numbers of Cryptosporidium
while other surfaces are
spared.
(Left) The acid-fast technique
for stool strongly stains
Cryptosporidium cysts red,
while tissue AFB staining
does not. In this acid-fast
stain, the organisms are
visible on counterstain in
large numbers. (Right) A
small bowel biopsy on acidfast stain with innumerable
Cryptosporidium (seen on
counterstain) is shown with
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
an almost continuous layer of
arasites disrupting the brush
border.
(Left) In this PAS stain
of the small bowel, the
Cryptosporidium parasites
disrupt the uniform dark pink
brush border focally with
several parasites visible on
the surface . (Right) A
case of Cryptosporidiosis in
the small bowel as seen on
PAS stain shows a uniform
ink brush border interrupted
by occasional parasites
appearing as blue to purple
dots.
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CRYPTOSPORIDIOSIS AND OTHER COCCIDIA INFECTIONS
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Microscopic Features
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
(Left) Cystoisospora in
the small bowel epithelium
appears in the upper 1/3
and often has a halo around
the organism. Cyclospora
appears very similar,
although often with multiple
forms in 1 cell. (Right) The
asexual and sexual stages
of the Cystoisospora in
the epithelium may stain
the same as or slightly paler
than the human epithelial
cell nuclei adjacent, making
distinguishing them very
challenging.
(Left) Hematoxylin & eosin
section shows crescentshaped Cystisospora
asexual forms and ovoid
sexual forms within
arasitophorous vacuoles.
(From DP: Gastrointestinal.)
(Right) A wet mount of
stool from a patient with
cryptosporidiosis shows the
very small, round bodies
(4-6 m), which may
be extremely difficult to
diagnose without modified
acid-fast staining. (Courtesy
P. Drotman, MD, CDC/
PHIL.)
(Left) Fresh stool sample on
FB shows small, round,
red Cryptosporidium
FB staining is the ideal way
to diagnosis this parasite
on a stool sample being
reviewed for ova and
arasites. Antigen testing for
Cryptosporidium is more
sensitive and specific but
does not capture other
arasites. (Right) Cyclospora
on stool smear after AFB
staining shows almost
erfectly round, variably
ositive cysts, some staining
and nonstaining .
(Courtesy M. Moser, CDC/
PHIL.)
.
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ENTAMEBIASIS
Iron-hematoxylin permanent stool mount from a patient
with Entamoeba histolytica shows cysts with
chromatid bodies and trophozoites with ingested
red blood cells.
TERMINOLOGY
Synonyms
Amebic dysentery
Amebiasis
Definitions
Latin: "Ent" (intestine, internal) + Greek:
"Amoiba" (change, alteration)
Latin: "Histo" (tissue) + "lytica" (lyses)
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Poor sanitation and exposure to water contaminated
with human feces
Humans are the only known reservoir for Entamoeba
histolytica
Fecal-oral and sexual transmission occurs
Men who have sex with men (MSM) have higher
incidence than general population
Infectious Agents
Entamoeba contains many species including E.
histolytica, Entamoeba dispar, Entamoeba moshkovskii,
Entamoeba polecki, Entamoeba coli, and Entamoeba
hartmanni
Entamoeba histolytica ("lyser of tissue") is the only
one associated with disease
Entamoeba are anaerobic, eukaryotic, parasitic
protozoan
CLINICAL ISSUES
Epidemiology
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~ 50 million cases of invasive E. histolytica disease
occur each year worldwide
Area of necrosis from a liver abscess caused
by disseminated Entamoeba histolytica demonstrates
numerous trophozoite forms within a sea of necrosis.
Minimal inflammation is present due to lysis.
Commonly affects people in tropical areas with poor
sanitary conditions
Prevalence of amebiasis in United States is ~ 4%
E. histolytica is transmitted via ingestion of cystic form
Excystation then occurs in terminal ileum or colon,
resulting in trophozoites
Presentation
Dysentery (bloody diarrhea)
Fulminant colitis
Toxic megacolon
Invasive extraintestinal disease
Liver abscess, pleuropulmonary disease, pericarditis,
brain abscess, peritonitis, and genitourinary disease
Treatment
Asymptomatic amebiasis: Iodoquinol, paromomycin,
or diloxanide furoate
Amebic colitis: Nitroimidazole derivative,
paromomycin
Amebic liver abscess: Drainage or metronidazole
Prognosis
Mortality is related to extent of dissemination and lack
of treatment
Toxic megacolon can present with bacteria sepsis with
high mortality
IMAGE FINDINGS
Ultrasonographic Findings
To evaluate amebic liver abscess, which is solitary
homogeneous, hypoechoic, round lesion
MICROSCOPIC PATHOLOGY
Histologic Features
Gastrointestinal disease
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ENTAMEBIASIS
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
Etiology
Entamoeba contains many species but E. histolytica
("lyser of tissue") is the only one associated with
disease
Clinical Issues
E. histolytica is transmitted via ingestion of cystic
form
Dysentery (bloody diarrhea)
Invasive extraintestinal disease
Microscopic Pathology
Gastrointestinal
Mucosal thickening, multiple discrete ulcers
separated by regions of normal-appearing colonic
mucosa
Mucosal thickening, multiple discrete ulcers
separated by regions of normal-appearing colonic
mucosa
Diffuse inflammation and edematous mucosa,
necrosis, or wall perforation
Flask-shaped ulcer of amebic colitis
Disseminated disease
Acellular abscess containing necrotic debris,
trophozoites, and variable rim
Minimal inflammation may be present due to direct
cell lysis by parasite
Cytologic Features
Liver abscess aspirate is usually thick, yellow-brown
liquid classically referred to as "anchovy paste"
Amebae may be rarely seen and no inflammatory cells
are present in aspirate
ANCILLARY TESTS
PCR
Performed on stool or tissue samples
Wide variety of PCR-based methods targeting different
genes, including 18S rDNA
Serologic Testing
ELISA testing uses monoclonal antibodies against
galactose/N-acetylgalactosamine (GAL/GalNAc), which
is specific lectin of Entamoeba histolytica with up to
100% sensitivity and specificity
Other ELISA kits use monoclonal antibodies against
serine-rich antigen
Stool Examination
Microscopic examination of fresh stool smears for
trophozoites that contain ingested red blood cells
3 stool samples over no more than 10 days can
improve detection rate to 85-95%
Stool examination cannot distinguish E. histolytica
from nonpathogenic Entamoeba dispar and Entamoeba
moshkovskii
Key Facts
Disseminated disease
Top Differential Diagnoses
Gastrointestinal bloody diarrhea
Pyogenic bacterial hepatic abscesses
Culture
Complex system not used for routine diagnosis with
success rate of 50-70%
DIFFERENTIAL DIAGNOSIS
Enteroinvasive or Enterohemorrhagic
Escherichia coli Infections
Absence of parasites, positive stool cultures
Negative ELISA and PCR for E. histolytica
Shigella Species Infections
Fecal leukocytes, which are absent or rare in E.
histolytica
Fresh blood in stool
Pyogenic Hepatic Abscesses
Microorganisms most commonly isolated from blood
and abscess cultures include E. coli, Bacteroides species,
Streptococcus species, and others
Can be cryptogenic in 1/2 of cases (no cause)
Campylobacter Infections
Positive Gram stain of stool samples for characteristic
curved rods organisms
ELISA or PCR are specific for detecting Campylobacter
jejuni
SELECTED REFERENCES
1. Goswami A et al: Colonic involvement in amebic
2. Quach J et al: The future for vaccine development against
3. Moonah SN et al: Host immune response to intestinal
4. Barratt JL et al: Importance of nonenteric protozoan
Diffusely inflamed and edematous mucosa,
necrosis, or wall perforation
Flask-shaped ulcer of amebic colitis
Acellular abscess containing necrotic debris,
trophozoites, and variable rim
Liver abscess aspirate is usually thick, yellow-brown
liquid classically referred to as "anchovy paste"
Minimal inflammation may be present due to
direct cell lysis by parasite
Escherichia coli
Shigella species infections
Campylobacter infections
liver abscess: does site matter? Ann Gastroenterol.
27(2):156-161, 2014
Entamoeba histolytica. Hum Vaccin Immunother.
10(6):1514-21, 2014
amebiasis. PLoS Pathog. 9(8):e1003489, 2013
infections in immunocompromised people. Clin Microbiol
Rev. 23(4):795-836, 2010
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ENTAMEBIASIS
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Microscopic Features
(Left) Transmural section of
colon in a case of invasive
Entamoeba histolytica
demonstrates edema, necrosis
of the epithelium , and
loss of architecture. (Right)
Numerous Entamoeba
histolytica trophozoites
are seen at high power within
the edema of the colon in
an invasive case of infection.
Within several of the protozoa,
black digested hemoglobin
igment can be seen .
(Left) Numerous Entamoeba
histolytica trophozoites
are seen at high power within
the edema of the colon in
an invasive case of infection.
Within several of the protozoa,
ingested red blood cells
can be seen. (Right)
n Entamoeba histolytica
trophozoite is seen at high
ower within the edema of
the colon in an invasive case
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
of infection. The presence
of a pseudopodia on the
amoeba aids in distinguishing
it from inflammatory cells.
(Left) Entamoeba histolytica
trophozoites are seen
at high power in the colon
in an invasive case of
infection on trichrome stain.
Ingested red blood cells
distinguish these pathogens
from nonpathogen amoeba.
(Right) Numerous Entamoeba
histolytica trophozoites
are seen on trichrome stain at
high power within edema of
the colon in an invasive case
of infection. Note the lack of
inflammation relative to the
organism burden.
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Microscopic Features
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
ENTAMEBIASIS
(Left) A large liver abscess
from a patient with
disseminated Entamoeba
histolytica shows large areas
of necrosis with little
inflammatory reaction due
to lysis by the protozoa.
(Right) High magnification
of liver parenchyma in
an Entamoeba abscess
demonstrates edema
, scattered chronic
inflammation , and
numerous Entamoeba
histolytica trophozoites .
(Left) High magnification
shows liver parenchyma
with numerous Entamoeba
histolytica trophozoites
in a disseminated
case. When the staining of
sections makes the organism
more subtle, searching for
ingested red blood cells
can be extremely helpful for
confirming the diagnosis.
(Right) Low-power view
shows colon with severe
edema, loss of mucosa, and
minimal inflammation in a
case of invasive Entamoeba
histolytica.
(Left) High magnification
of colon with invasive
Entamoeba histolytica
demonstrates numerous
trophozoites , some of
which contain ingested red
blood cells . (Right) In
this section of colon on
Trichrome stain with invasive
Entamoeba histolytica, many
trophozoites are present
with pale, nondescript
nuclei unlike the human
inflammatory cells around
them, which show purple
nuclei
blood cells
some trophozoites.
. Ingested red
are seen in
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GIARDIASIS
Giardia lamblia cyst from stool is shown on an ironhematoxylin stain. Note the nuclei and parabasal
bodies as well as the distinct outline of the cyst.
TERMINOLOGY
Definitions
Infection by the protozoan Giardia lamblia
Named after French biologist Alfred M. Giard and
after Czech physician Vilm Lambl
ETIOLOGY/PATHOGENESIS
Infectious Agents
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
G. lamblia: Protozoa found in water and stool of
humans and animals
Transmission by ingestion of cysts
Fecal-oral transmission: Contaminated food and
water
CLINICAL ISSUES
Epidemiology
Affects 2% of adults and 6-8% of children in
developed countries
Most common intestinal parasitic disease in USA
20,000 cases reported per year, but true incidence
likely much higher
1/3 of those in developing countries have been
infected
Rates of infection appear to increase during summer
months in USA
Some strains may infect both humans and animals,
but transmission from animal to human is extremely
rare
Presentation
Incubation period of 1-3 weeks between ingestion of
cysts and onset of symptoms
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Those infected may remain asymptomatic but can
shed the organism
Small bowel biopsy from a young patient with diarrhea
demonstrates large numbers of Giardia trophozoites
around and adherent to the mucosa.
Acute infection presents as diarrhea with steatorrhea,
flatulence, abdominal pain, nausea, vomiting
Symptoms can last up to 4 weeks
Chronic infection can lead to chronic steatorrhea and
malabsorption with significant weight loss
Infected patients can shed 1-10 billion cysts daily in
their feces, which can continue for several months
Treatment
Metronidazole
Prognosis
Poorer outcomes associated with severe infection in
infants or immunocompromised
Risk Factors
Travel to high-prevalence areas
Child care settings
Drinking fresh river or lake water
Men who have sex with men
MICROBIOLOGY
Parasite Features
2 main forms: Cysts and trophozoites
Trophozoites attach to duodenal and jejunal mucosal
surface but do not invade mucosa
Diarrhea is thought to result from a combination of
malabsorption and hypersecretion in small intestine
Cysts are oval (11-14 m), contain 4 nuclei, 4
axonemes, and 4 median bodies
Trophozoites are pear-shaped (10-20 m), contain 2
nuclei, a sucking disk, 4 pairs of flagella, 2 axonemes,
and 2 median bodies
As few as 10 cysts are sufficient to cause infection
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Etiology
Transmission by ingestion of cysts, which can occur
from contaminated food and water
Clinical Issues
Acute infection presents as diarrhea with steatorrhea,
flatulence, abdominal pain, nausea, vomiting
Chronic infection can lead to chronic steatorrhea and
malabsorption with significant weight loss
GIARDIASIS
Key Facts
Microscopic Pathology
Organisms are purple to pink bodies with a tapered
end on mucosa
Cysts visible on fresh smear (saline suspension of
feces)
Diagnostic Checklist
Consider giardiasis in setting of diarrhea with
steatorrhea of > 1 week duration
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
MICROSCOPIC PATHOLOGY
Histologic Features
Organisms are seen on surface of mucosa as purple to
pink bodies with a tapered end
Changes in mucosa may be subtle to severe
(depending on chronicity)
Rarely see villous atrophy
Increased crypt depth with shortening of microvilli
Biopsies are commonly done in cases of diarrhea to
rule out other possible causes of symptoms
Trichrome stain will highlight organisms
ANCILLARY TESTS
Immunofluorescence
Direct fluorescent antibody testing of feces
Stool Examination
Light microscopic exam for morphological detection
Cysts &/or trophozoites are visible on fresh smear
(saline suspension of feces)
Formalin preparation for permanent staining
Enzyme-linked immunosorbent assay for antigen
detection
Immunochromatographic assay for antigen detection
(rapid test)
DIFFERENTIAL DIAGNOSIS
Infectious
Amebiasis, viral gastroenteritis, cryptosporidiosis,
strongyloidiasis
Differentiate based on morphological ova and
parasite examination of stool and antibody testing
Noninfectious
Irritable bowel syndrome lacks mucosal abnormalities
on biopsy
Celiac disease (severe villous atrophy, hyperplastic
crypts, lymphocytic infiltrate, and plasma cells in
lamina propria)
Lactose intolerance (hydrogen breath test)
Cystic fibrosis (chloride sweat test and genetic testing)
DIAGNOSTIC CHECKLIST
Pathologic Interpretation Pearls
Consider giardiasis in setting of diarrhea with
steatorrhea of > 1 week duration
SELECTED REFERENCES
1. Centers for Disease Control and Prevention. Parasites
- Giardia. http://www.cdc.gov/parasites/giardia/
epi.html#general. Updated July 13, 2012. Accessed
December 15, 2014
2. McHardy IH et al: Detection of intestinal protozoa in the
clinical laboratory. J Clin Microbiol. 52(3):712-20, 2014
IMAGE GALLERY
(Left) Flagellated Giardia lamblia trophozoite on an iron-hematoxylin stain demonstrates nuclei and lack of cyst wall. (Center) Duodenal aspirate
demonstrates pear-shaped Giardia lamblia trophozoites. (Courtesy Franz von Lichtenberg Collection of Infectious Disease Pathology, BWH.)
(Right) Duodenal mucosal atrophy in chronic giardiasis is shown. The biopsy lacks plasma cells. (Courtesy Franz von Lichtenberg Collection of
Infectious Disease Pathology, BWH.)
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MICROSPORIDIOSIS
High-power electron micrograph shows the
pathognomonic polar tube coils , a unique structure
of microsporidia spores. Here, 5 coils are present, typical
of E. intestinalis. (From DP: Kidney.)
TERMINOLOGY
Definitions
Greek: "Mikros" (small) + "sporos" (seed)
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Ubiquitous organisms, extensive host range
Infection: Ingestion or inhalation of microsporidia-
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
resistant spores
Infectious Agents
Microsporidiosis: Disease caused by obligate
intracellular pathogens recently assigned to the
kingdom Fungi
Spores of species associated with human infection
measure 1-4 m
1,500 species identified of > 1 million suspected
species
Human pathogens: Anncaliia (formerly Brachiola)
algerae, Anncaliia connori, Anncaliia vesicularum,
Encephalitozoon cuniculi, Encephalitozoon hellem,
Encephalitozoon intestinalis, Enterocytozoon bieneusi,
Microsporidium ceylonensis, Microsporidium africanum,
Nosema ocularum, Pleistophora spp., Trachipleistophora
hominis, Trachipleistophora anthropophthera, Vittaforma
corneae, and Tubulinosema acridophagus
CLINICAL ISSUES
Small bowel with microsporidiosis shows a diagnostic
form within cytoplasm of an epithelial cell. Note the
goblet cells in which mucin stains more blue, whereas the
microsporidium is darker.
Cases have been reported in immunocompetent
individuals
Presentation
Gastrointestinal microsporidiosis
Chronic diarrhea, abdominal pain, nausea,
vomiting, and weight loss
Ocular microsporidiosis
Blurred vision, foreign body sensation, pain,
redness, and tearing
Disseminated microsporidiosis
Musculoskeletal (myalgia, weakness), CNS
(headache, seizure), dermatologic (nodular lesions)
Laboratory Tests
Body fluid specimens
Modified trichrome-stained stool samples show
ovoid, refractile spores with bright red wall around
organism
Stool O&P tests for other parasites and bacteria are
negative
Fecal WBCs are usually absent
Rapid Gram chromotrope shows spores that stain
dark violet with enhanced equatorial stripe
Fluorochrome stains can be used to detect
microsporidia in urine, stool, mucus, and tissue
sections
Urine is useful for disseminated disease
Treatment
Albendazole
Thalidomide (unresponsive chronic diarrhea)
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Epidemiology
Opportunistic disease that affects
immunocompromised patients (e.g., AIDS and
transplant patients)
Generally occurs when CD4+ T-cell counts fall below
150 in HIV patients
MICROSCOPIC PATHOLOGY
Histologic Features
Mild to severe villous blunting with mild lymphocytic
infiltrate
MICROSPORIDIOSIS
Terminology
Microsporidiosis is an obligate intracellular pathogen
Clinical Issues
Microsporidiosis is an opportunistic disease that
affects immunocompromised patients (e.g., AIDS and
transplant patients)
Microscopic Pathology
Stain poorly with hematoxylin & eosin
Key Facts
Villous blunting may be mild to severe
Mild lymphocytic inflammatory infiltrate
Organisms identified as clusters within supranuclear
cytoplasm of epithelial cells (2-3 m spores)
Top Differential Diagnoses
Cryptosporidium
Cytomegalovirus infection
Giardiasis
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
Organisms (poorly staining on H&E) identified as
clusters within supranuclear cytoplasm of epithelial
cells (2-3 m spores)
ANCILLARY TESTS
Histochemistry
Gram stain, Warthin-Starry silver stain, Giemsa stain,
and trichrome blue stain
Filament within spores may polarize
PCR
Useful for detection (and excluding differential
diagnosis) but is species specific, so sensitivity is
limited
Electron Microscopy
Transmission EM to diagnose genus
DIFFERENTIAL DIAGNOSIS
Cryptosporidiosis, Cyclosporiasis,
Cystisosporiasis
Modified acid-fast stain: Identifies coccidian oocysts in
concentrated stool specimen
Does not work on tissue forms of parasites
High concentration of oocysts (all larger than
microsporidia) is seen in small bowel biopsy
On surface: Cryptosporidium
In cytoplasm as banana shapes: Cyclospora
In cytoplasm as large round/oval shapes:
Cystisospora
Cytomegalovirus Infection
Intracellular inclusions surrounded by clear halo in
tissue biopsy
Positive IHC, PCR, or antibody tests for CMV
Giardiasis
Stool examination for trophozoites (leaf-shaped with 2
nuclei and 4 pairs of flagella) or cysts (smooth walled
and oval with curved median bodies, axonemes, and
nuclei)
Microsporidia lack flagella, are intracytoplasmic,
very small
Stool antigen enzyme-linked immunosorbent assay
(ELISA) when 3 O&P tests are negative
SELECTED REFERENCES
1. Meissner EG et al: Disseminated microsporidiosis
in an immunosuppressed patient. Emerg Infect Dis.
18(7):1155-8, 2012
2. Tham AC et al: Clinical spectrum of microsporidial
keratoconjunctivitis. Clin Experiment Ophthalmol.
40(5):512-8, 2012
3. Didier ES et al: Microsporidiosis: not just in AIDS patients.
Curr Opin Infect Dis. 24(5):490-5, 2011
4. Anane S et al: Microsporidiosis: epidemiology, clinical data
and therapy. Gastroenterol Clin Biol. 34(8-9):450-64, 2010
MICROSCOPIC FEATURES
(Left) A severe case of microsporidiosis shows florid numbers of infected cells in the epithelium with villus blunting. (Center) Gram stain
shows microsporidia spores
consisting of a plastic-embedded thick section for electron microscopy shows spores
DP: Gastrointestinal.)
and plasmodia . Spores resemble gram-positive cocci. (From DP: Gastrointestinal.) (Right) Specimen
, as well as plasmodial forms of microsporidia. (From
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