Page 437 - Review of Medical Microbiology and Immunology ( PDFDrive )

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PART VI Parasitology
TABLE 51–2 Features of Medically Important Protozoa
Organism
United States
Treatment
I. Intestinal and urogenital protozoa
Entamoeba
serology
Giardia
Ingestion of cysts in food
Yes
Metronidazole
Trophozoites or cysts in stools
Cysts on acid-fast stain
Ingestion of cysts in food
Yes
Paromomycin may be useful
Cryptosporidium Ingestion of cysts in food Yes Trophozoites or cysts in stool; Metronidazole or tinidazole
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Yes
Metronidazole
Sexual
Trophozoites in wet mount
Trichomonas
II. Blood and tissue protozoa
Trypanosoma
T. cruzi
xenodiagnosis
1
Suramin
T. gambiense,
No
Tsetse fly
Blood smear
T. rhodesiense
Leishmania
L. donovani
lymph node
Stibogluconate
L. tropica, L. mexicana,
Fluid from lesion
Sandfly
No
L. braziliensis Sandfly No Bone marrow, spleen, or Stibogluconate
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mebooksfree.com mebooksfree.com Anopheles mosquito No Blood smear Chloroquine if sensitive; mefloquine mebooksfree.com
Plasmodium
Rare
Blood smear
Chloroquine if sensitive; also prima-
P. vivax, P. ovale,
Anopheles mosquito
quine for P. vivax and P. ovale
P. malariae
P. falciparum
or quinine plus doxycycline or
Malarone or artemisinins if resistant
Yes
Serology; microscopic exami-
Ingestion of cysts in raw
Sulfadiazine and pyrimethamine for
Toxoplasma
meat; contact with cat
nation of tissue; mouse
congenital disease and immuno-
feces
inoculation
compromised patients
Pneumocystis
Lung biopsy or lavage
Yes
Trimethoprim-sulfamethoxazole; also
Inhalation
pentamidine or atovaquone
1
Melarsoprol is used if the central nervous system is involved.
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the stool: one detects E. histolytica antigen, and the other
polymorphonuclear leukocytes are seen, whereas in amebic
detects nucleic acids of the organism in a polymerase chain
dysentery, they are not.
reaction (PCR)-based assay.
Serologic testing is useful for the diagnosis of invasive
A complete examination for cysts includes a wet mount
in saline, an iodine-stained wet mount, and a fixed,
amebiasis. The indirect hemagglutination test is usually
positive in patients with invasive disease but is frequently
trichrome-stained preparation, each of which brings out
different aspects of cyst morphology. These preparations
negative in asymptomatic individuals who are passing
cysts.
are also helpful in distinguishing amebic from bacillary
TABLE 51–3 Medically Important Stages in Life Cycle of Intestinal Protozoa
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Stage That Infects
Outside of Humans
Stage(s) in Humans Most Associated with Disease
Insect Vector
Humans
Organism
Entamoeba
Cyst
Cyst
Trophozoites cause bloody diarrhea and liver abscess
None
None
Giardia
Cyst
Cyst
Trophozoites cause watery diarrhea
Cyst
Cryptosporidium
Trophozoites cause watery diarrhea
None
Cyst
None
Trophozoites cause vaginal discharge
Trophozoite
None
Trichomonas
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