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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_182_библиотеки_им_акад_М_И_Перельмана.pdf
(Left) Low-power view of liver
p
in a patient with disseminated
trichosporonosis shows
areas of vascular invasion/
hematogenous spread
and necrosis . (Right) High
magnification of a vessel filled
with Trichosporon fungi
admixed with blood is shown
from a liver in disseminated
disease.
(Left) Section of bowel
wall from a patient with
disseminated trichosporonosis
shows a subtle collection
of fungi within the
muscularis with no associated
inflammation. (Right) High
magnification of a vessel and
adjacent muscle demonstrates
invasive Trichosporon with
hyphae extending into
tissue with no inflammatory
response.
TRICHOSPORONOSIS
Microscopic Features
Fungal Infections: Challenging Morphology in Fungal Infections Requiring Culture/Ancillary Tests
(Left) Arthroconidia are
resent at the edge of this
mass of fungus consistent with
trichosporonosis. (Right) A
section of myocardium from
a patient with disseminated
trichosporonosis shows
a collection of fungus
invading tissue with minimal
inflammatory response, and
the formation of arthroconidia
.
III
2
10
Special Stains
p
p
f
A
Fungal Infections: Challenging Morphology in Fungal Infections Requiring Culture/Ancillary Tests
TRICHOSPORONOSIS
(Left) Low-power view of a
liver on silver stain from a
atient with disseminated
trichosporonosis shows
multifocal necrotic
collections with
thriving fungi giving
the gross appearance
of "shotgun blasts" to
the liver parenchyma.
(Right) Low-power view
of a bronchus in a
atient with disseminated
trichosporonosis shows
dense collections of fungi
in the bronchial wall
and causing large areas of
necrotizing pneumonia .
(Left) Medium-power view o
a collection of Trichosporon
fungus shows the formation
of arthroconidia . (Right)
more difficult image is
shown of Trichosporon
where arthroconidia are not
easily identified and invoke
a differential diagnosis of
candidiasis and aspergillosis.
(Left) Disseminated
trichosporon where
arthroconidia are not easily
identified even at high power
can appear very similar
to other fungi, including
hyalohyphomycoses.
(Right) The presence of
arthroconidia in the
correctly susceptible host
should prompt a consistent
diagnosis with disseminated
trichosporonosis, which
should be confirmed with
culture or PCR.
III
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SECTION 1
Morphologic Diagnosis of
IV-1-2
Gastrointestinal and
Other Luminal Protozoa
Balantidiasis IV-1-4
IV-1-6
Entamebiasis IV-1-10
Giardiasis IV-1-14
Microsporidiosis IV-1-16
Trichomoniasis IV-1-18
Intravascular Protozoa
African Trypanosomiasis IV-1-20
Babesiosis IV-1-22
Malaria IV-1-24
Deep Tissue Protozoa
IV-1-34
American Trypanosomiasis IV-1-40
Leishmaniasis IV-1-42
Toxoplasmosis IV-1-46
PROTOZOA CLASSIFICATION AND DIAGNOSIS
TERMINOLOGY
Definitions
Protozoan: Single-celled eukaryotic organism
(outdated terminology)
Pathogen: Causes human symptomatic disease
Parasite: Completes part of life cycle within host
Definitive: Reproduces sexually inside host (also
referred to as "final" or "primary")
Intermediate: Changes stage but reproduces only
asexually or not at all inside host
Direct: Infects a single species without an intermediate
host
Indirect: Infects several species ("complex") an
intermediate host
Obligate: Must pass through a specific host
Facultative: May pass through a host
Accidental: Enters a host in which it cannot complete
life cycle
Paratenic: Passes through host without reproducing or
changing stage
Free living: Protozoan able to complete life cycle
without a host
CLINICAL ISSUES
Parasite &/or Pathogen
Parasitic infection results in some detriment to
infected host
Direct competition for nutrition (hypoglycemia)
Plasmodium
Chronic nutritional challenges (anemia,
malnutrition, growth retardation)
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
IV
Giardia, Plasmodium, Cryptosporidium
Disturbances of immune system (macrophage
dysfunction)
Leishmania
Pathogenic infections result in symptomatic, often
severe, disease
Direct tissue damage (necrosis of liver,
microhemorrhages)
Entamoeba histolytica, Plasmodium, Toxoplasma
Space occupying effects (hepatosplenomegaly)
Leishmania
Failure of immune system (as opportunistic
infection)
Leishmania, Entamoeba, Balantidium
Human host can determine protozoan behavior as
parasite or pathogen
Toxoplasma
Asymptomatic disease in normal hosts or mild
acute lymphadenopathy
Severe necrotizing disease in newborns and
immunosuppressed
Cryptosporidium
Asymptomatic in normal host at low
concentration
Watery diarrhea in normal host at high
concentration
Severe diarrhea in immune compromised host
Pathogens effect host regardless of immune status
1
Naegleria fowleri
Free-living amoeba incidentally enters human
Nearly 100% fatal; limited treatment options
(2013: 2 surviving patients)
Trypanosoma brucei rhodesiense
Zoonosis
100% fatal without treatment
PROTOZOA CLASSES
Ciliates
Protozoa covered with hundreds of cilia
Balantidium coli
Gastrointestinal tract pathogen (only known human
ciliate pathogen)
Many nonpathogen species are ubiquitous in water
sources and may be found in human samples
Flagellates
Protozoan having 1 flagella
Giardia lamblia
Gastrointestinal tract pathogen
Trichomonas tenax
Oral commensal flagellate
Amoeba
Protozoa without definitive shape, which move
through pseudopodia
Entamoeba histolytica
Gastrointestinal tract pathogen
May invade mucosa and disseminate to liver, brain
Entamoeba coli
Gastrointestinal tract parasites (nonpathogen)
One of many nonpathogenic amoeba
May indicate exposure to unclean water supply
Free-living amoeba ("terrameoba") that enter humans
Naegleria fowleri: Nearly 100% fatal
Acanthamoeba, Balamuthia: Immunosuppressed
hosts
Apicomplexa
Coccidia
Protozoa that are obligate intracellular parasites,
often of gastrointestinal tract
Opportunistic coccidia pathogens
Cryptosporidium
Cytoisospora
Cyclospora
Blood-borne
Protozoa that are obligate intracellular parasites
found in peripheral blood
Plasmodium: Cause human malaria
Plasmodium falciparum: Severe human disease with
mortality
Plasmodium vivax, Plasmodium ovale: Recurrent
human malaria (liver hypnozoite stage)
Babesia: Cause human babesiosis
Increase pathology in splenectomized patients
Share Ixodes vector with Borrelia and Anaplasma
Zoonotic
Protozoan that are obligate intracellular parasites
of other definitive hosts, accidentally found in
humans (cannot transmit/complete life cycle)
2
PROTOZOA CLASSIFICATION AND DIAGNOSIS
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
Toxoplasma gondii
Deep tissue opportunistic pathogen commonly
from feline sources
Kinetoplastids
Protozoa having 1 flagellum and a kinetoplast
organelle resulting in systemic disease
Trypanosoma
African sleeping sickness, Chagas disease
Leishmania
Cutaneous, mucocutaneous, and visceral
leishmaniasis
DIAGNOSTIC APPROACHES TO PROTOZOA
Stool Examination
Fresh examination (within 1 hour of collection) for
trophozoites &/or cysts
Formalin fixation (no time limitation) for cysts
PVA fixation (no time limitation) for trophozoites &/
or cysts
Size range of intestinal protozoa is 4 m
(Cryptosporidium) to 200 m (Balantidium)
Iodine stain
Fresh or formalin-fixed stool
Rapid, for visualization in wet mounts
Modified acid-fast stain
Fresh or formalin-fixed stool
Intestinal coccidia species
Trichrome stain
Fresh, polyvinyl alcohol (PVA), or Schaudinn
fixative
Intestinal protozoa, yeast
Iron hematoxylin stain
Fresh, sodium acetate, acetic acid, formalin (SAF), or
PVA
Permanent stain for intestinal protozoa
Modified iron hematoxylin stain
SAF fixative
Adds acid-fast detection for coccidia species
A variety of other staining techniques are available for
both classes and specific parasite species
Peripheral Blood Smear
Thin smear
20 L blood on clean glass slide
Quantification and speciation of malaria, Babesia,
trypanosomes
Thick smear
20-40 L of blood on clean glass slide
Rapid screening for parasites
Wright-Giemsa stain
Standard blood film stain highlights all protozoan
Does not highlight Schffner dots (Plasmodium)
optimally
Giemsa stain
Standard stain for blood stage protozoa
Accentuates Schffner dots for malaria speciation
Cytology and Fine-Needle Aspiration
Cerebrospinal fluid
Free-living amoeba
Liver mass, brain mass, large abscess
Entamoeba
Bone marrow
Leishmania
Cervical Pap smear
Trichomonas
Skin nodules
Leishmania (or touch preps of fresh biopsy)
Lymph nodes
Trypanosoma
Hepatosplenomegaly
Leishmania
Tissue Biopsy
Gastrointestinal tract
Invasive or adherent organisms
Giardia, Entamoeba, Balantidium
Skin, liver, spleen
Cutaneous or visceral Leishmania
Lymph node
Toxoplasma
Serology
Presence of antibodies to a given pathogen in patient’s
blood
Useful for patients without chronic exposure history
Travelers, military personnel
Not useful for patients with chronic exposure history
Immigrants from endemic areas or a history of prior
infection
Invasive infections may produce positive serology
Rapid Diagnostic Tests
Parasite antigen-based detection for rapid diagnosis
Lateral flow assays most common
As sensitive or more sensitive than microscopy
Plasmodium, Giardia, Cryptosporidium, Entamoeba
Molecular Diagnostics
Detection of parasite RNA/DNA
Helpful in difficult differential diagnoses
Plasmodium vs. Babesia
SELECTED REFERENCES
1. Diagnostic Procedures. DPDx: Laboratory Identification
of Parasitic Diseases of Public Health Concern. Centers for
Disease Control and Prevention. http://www.cdc.gov/dpdx/
diagnosticProcedures/index.html. Updated November 29,
2013. Accessed September 17, 2014
2. Ova and Parasite (O&P) Examinations. PARA-SITE
Online. http://www.med-chem.com/para-site.php?
url=procedures&subsection=microscopic. Accessed
September 17, 2014
3. Practical Parasitology: A Preview. Practical Science.
practicalscience.com/contents.html. Accessed September
17, 2014
IV
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BALANTIDIASIS
The colon of a patient with balantidiasis demonstrates
multiple ulcers in the mucosa. (Courtesy R. Neafie,
MD.)
TERMINOLOGY
Definitions
Greek: "Balantidion" (little bag) + "kolon" (colon)
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Normal host of parasite is pigs; humans are incidental/
accidental hosts after fecal-oral exposure
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
Also found in rats and other mammals, which may
be source in immunosuppressed patients
Natural disasters may lead to increased use of
contaminated water and outbreaks in normal hosts
Infectious Agents
Balantidium coli
Large (80-200 m) ciliated protozoan parasite
Requires adjustment to gastrointestinal tract
conditions from host to host
CLINICAL ISSUES
Epidemiology
Prevalence of 0.02-1% in human population,
depending on location
Found worldwide but endemic focus present in
Philippines
Consider in patients with travel history to Southeast
Asia, western Pacific Islands, or rural South America
Immunocompromised patients and individuals with
malnutrition or other gastrointestinal imbalances are
at highest risk
Presentation
IV
Asymptomatic carriage occurs
Active, acute disease with frequent, "explosive" bloody,
mucus-containing diarrhea (2-3x per hour)
1
A trophozoite of Balantidium demonstrates the
circumferential layer of cilia and the distinctive foot
print-shaped nucleus . Balantidium is the largest
protozoan parasite in humans.
Severe abdominal pain &/or sepsis may indicate
bowel perforation
Chronic disease with nonbloody diarrhea, cramping,
halitosis, and abdominal pain
Laboratory Tests
Stool examination for parasites will reveal large
ciliated protozoa as trophozoites or smaller cysts
May be enhanced by sedimentation or flotation
techniques
Bronchoalveolar lavage can reveal trophozoites,
which must be distinguished from ciliated respiratory
epithelial cells
Isolation of trophozoites from urine has been
demonstrated in patients with genitourinary
involvement (direct spread from colon)
Treatment
Tetracycline for gastrointestinal diarrheal disease
Surgical resection may be required for perforation
Prognosis
Uncomplicated disease is easily treated with
medication
Severe abdominal disease with perforation may be life
threatening (30% mortality)
MICROBIOLOGY
Parasite Characteristics
Only ciliate that infects humans/causes
gastrointestinal disease
Measures 15-30 m in length by 25-120 m in width
as trophozoite
Measures 40-60 m in diameter and is spherical or
ovoid as cysts
Culture
No role in diagnosis of balantidiasis
4
Etiology
Balantidium coli: 80-200 m ciliated protozoan
parasite
Clinical Issues
Found worldwide (endemic in Philippines)
Frequent, "explosive" bloody, mucus-containing
diarrhea; risk of perforation
BALANTIDIASIS
Key Facts
Microscopic Pathology
Gastrointestinal tract: Loss of mucosa, severe acute
inflammation, edema, and perforation
Trophozoites are covered cilia with large
macronucleus
Top Differential Diagnoses
Entamoebiasis, bacillary dysentery, ulcerative colitis
&/or Crohn disease
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
MACROSCOPIC FEATURES
Gastrointestinal Tract
Ulcerative colitis, gangrenous appendix, frank
perforation with fibrinous peritonitis
MICROSCOPIC PATHOLOGY
Histologic Features
Gastrointestinal tract
Ulcerative colitis with loss of mucosa, severe acute
inflammatory infiltrates, edema, and penetration of
bowel wall (perforation)
Organisms appear as large, round to oval bodies
covered in fine cilia layer (similar appearance to
brush border of intestine) with large, dark blue to
black macronucleus
Appendicitis with neutrophilic infiltrates and
organisms can occur
Neutrophilic peritonitis with organism in ascitic
fluid can occur
Lung (rare)
Hematogenous spread to lungs from colon has lead
to discrete lesions of frank neutrophilic pneumonia
with necrosis containing organisms
Osteomyelitis (extremely rare)
Purulent abscess of spine containing B. coli
trophozoites has occurred
DIFFERENTIAL DIAGNOSIS
Entamoebiasis
Clinically similar history and presentation with
stool examination revealing Entamoeba histolytica
trophozoites or cysts
Histologically, appears very similar to balantidiasis but
with distinctive flask-shaped lesions and trophozoites
showing ingested red blood cells
Bacillary Dysentery
Positive stool cultures, lack of trophozoites in tissue,
milder inflammatory reaction
Ulcerative Colitis &/or Crohn Disease
Lack of organisms, uniformity of inflammation (
granulomas), and clinical history
DIAGNOSTIC CHECKLIST
Clinically Relevant Pathologic Features
Exposure to pigs strongly suggestive in normal hosts
Pathologic Interpretation Pearls
Large, ciliated trophozoites are distinctive and unique
SELECTED REFERENCES
1. Schuster FL et al: Current world status of Balantidium coli.
Clin Microbiol Rev. 21(4):626-38, 2008
MICROSCOPIC FEATURES
(Left) An iron-hematoxylin stain of permanent stool mount shows multiple Balantidium parasites . (Center) Medium-power view of the surface
of the mucosa in an invasive Balantidium infection shows remnant epithelium
propria. (Right) High magnification of a section of colon from a patient with invasive balantidiasis shows the large ciliated trophozoite
distinctive nucleus .
and scattered inflammation in the largely necrotic lamina
with its
IV
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CRYPTOSPORIDIOSIS AND OTHER COCCIDIA INFECTIONS
Cryptosporidium (2-5 m basophilic spherical structures,
oocysts) at the apical brush border of the intestinal
epithelial cells are intracytoplasmic but disrupt the brush
border.
TERMINOLOGY
Synonyms
Cryptosporidiosis
Cyclosporiasis
Cystoisosporiasis
Definitions
Greek: "Crypto" (hidden) + "sporos" (seed)
Modern and Greek: "Cyclo-" (round) + "sporos" (seed)
Greek: "Kustis" (cyst) + "isos" (equal) + "sporos" (seed)
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
+"belli" (beautiful)
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Cryptosporidiosis
Water contaminated with Cryptosporidium oocysts
(or spores)
Most common of human coccidian intestinal
parasites
Cyclosporiasis
Contaminated food and drink (water, vegetables,
fruits)
Most cases occur during spring and summer months
1/3 of cases in USA are acquired from Latin
America and Caribbean
Cystoisosporiasis
Contaminated water or institutionalization
Least common of 3 human coccidian intestinal
parasite infections
Infectious Agents
Cryptosporidium spp.
Microscopic coccidian parasite (4-6 m on
wet mount) in water causes diarrheal disease
IV
cryptosporidiosis
Cyclospora spp.
1
Cyclospora (round forms and crescent-shaped forms
) in parasitophorous vacuoles are most often present
in the surface epithelium in the upper 1/3 of epithelial
cells. (From DP: Endoscopic.)
Microscopic coccidian parasite (8-10 m on wet
mount) on fresh food or in water causes diarrheal
disease cyclosporiasis
C. cayetanensis infections have been identified only
in humans
Cystoisospora belli (formerly Isospora belli)
Large microscopic coccidian parasite (30 x 20 m
on wet mount) on fresh food or in water causes
diarrheal disease cystoisosporiasis
CLINICAL ISSUES
Presentation
Profuse watery diarrhea
Massive ingestion: Contaminated water during
water system failures leads to epidemic outbreaks of
cryptosporidiosis
Immunosuppression: Individual patient’s failing
immune system leads to amplified infection
Cystoisospora causes eosinophilia
Laboratory Tests
Stool examination
Conventional wet mount
Cryptosporidium and Cyclospora are very similar
except for size
Cystoisospora has unique oblong/oval shape with 2
oocysts inside
Modified acid-fast stain
All 3 coccidia are acid-fast
Cyclospora is variably acid-fast and organisms in
same field may be negative
Safranin stain
All 3 coccidia are orange to red, although more
variable than acid-fast
Autofluorescence
Cyclospora and Cystoisospora
Rapid antigen testing
Cryptosporidium: Highly sensitive and specific
6
CRYPTOSPORIDIOSIS AND OTHER COCCIDIA INFECTIONS
Etiology
Cryptosporidium species
Cyclospora cayetanensis
Cystoisospora belli
Clinical Issues
Profuse watery diarrhea
Stool examination
Cryptosporidium and Cyclospora are very similar
except for size
Cystoisospora has unique oblong oval shape with 2
oocysts inside
Modified acid-fast stain
All 3 coccidia are acid-fast
Cyclospora is variably acid-fast, and organisms in
same field may be negative
Key Facts
Microscopic Pathology
Cryptosporidium
Cyclospora and Cystoisospora
Top Differential Diagnoses
Microsporidiosis (often small bowel)
Giardiasis (small bowel)
Entamoebiasis (colon)
Protozoan Parasitic Infections: Morphologic Diagnosis of Protozoa in Anatomic Pathology
Small, round, bluish-purple bodies present at
luminal tips and surfaces of villi
Round to oval large inclusions within epithelial
cells
Located toward luminal surface but within
cytoplasm
Not available for other coccidia
PCR/molecular testing
Treatment
Drugs
Cryptosporidium
Usually self-limited, support with fluids,
nitazoxanide: Immunocompetent hosts
Reverse immunosuppression in
immunosuppressed hosts
Cyclospora and Cystoisospora
Trimethoprim-sulfamethoxazole, pyrimethamine
(if TS-allergic), ciprofloxacin (less effective)
Prognosis
Immunocompetent
Full recovery with no recurrence
Immunocompromised
Recovery with risk of recurrence
MICROBIOLOGY
Sporulation Assay
For distinguishing Cyclospora from other stool
organism, assayed over 3 weeks to monitor for
evidence of sporulation
Round forms (2-3 m) with parasitophorous vacuole
("halo")
Crescentic merozoites (5-6 m) with
parasitophorous vacuole
Cystoisospora
Located toward luminal surfaces of epithelial cells
but within cytoplasm
Schizonts and merozoites with crescentic or bananashaped forms
DIFFERENTIAL DIAGNOSIS
Microsporidiosis
Identification of microsporidia cysts in stool in an
infected patient via stool ova and parasite exam or by
electron microscopy on biopsy
On biopsy, microsporidia are small collections of
intracytoplasmic bodies in epithelial surface of colon
or small bowel, with villous blunting
Giardiasis
Identification of Giardia intestinalis trophozoites or
cysts in stool of infected patients via stool O&P
On biopsy, Giardia are purple, triangular, flagellated
bodies adherent to or floating near epithelial surface of
small bowel
MICROSCOPIC PATHOLOGY
Histologic Features
Coccidian infection of small bowel
Villous blunting in small bowel is usually mild
Surface epithelial cell disarray with apoptosis
Mildly increased surface intraepithelial lymphocytes
Cryptosporidium
Small, round, bluish-purple bodies present at
luminal tips and surfaces of villi of small bowel
Cyclospora
Located toward luminal surface of small bowel
epithelium but within cytoplasm
DIAGNOSTIC CHECKLIST
Clinically Relevant Pathologic Features
Travel to an endemic area, history of exposure in
epidemic outbreak, or immunosuppression with
watery diarrhea should prompt scrutiny
SELECTED REFERENCES
1. Bouzid M et al: Cryptosporidium pathogenicity and
virulence. Clin Microbiol Rev. 26(1):115-34, 2013
2. Legua P et al: Cystoisospora and cyclospora. Curr Opin
Infect Dis. 26(5):479-83, 2013
IV
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