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Figure 49-44 Cyclospora cayetanensis oocysts exhibiting autofluorescence. Photographed using high dry (x400). (Leftphotograph courtesy Charles R. Sterling, University of Arizona; right photograph courtesy E. Long, Centers for Disease Control and Prevention, Atlanta, Ga.)

Figure 49-44 Cyclospora cayetanensis oocysts exhibiting autofluorescence. Photographed using high dry (x400). (Leftphotograph courtesy Charles R. Sterling, University of Arizona; right photograph courtesy E. Long, Centers for Disease Control and Prevention, Atlanta, Ga.)

oocysts tend to be very acid-fast variable and some of the oocysts may resemble clear, wrinkled cellophane.

Sarcocystis spp, appear in Table 49-18 but are not discussed in detail. According to the literature, extraintestinal human sarcocystosis is rare, with a much lower incidence than that seen with the intestinal infection.

Microsporidia

The microsporidia are obligate intracellular parasites that can infect both animals and humans, through Ingestion, inhalation, or direct inoculation of the infective spores, which are environmentally resistant (Figures 19-45 and 49-46) (see Table 49-19). To date, eight genera have been recognized in humans: Brachiola, Encephalitozoon, Enterocytozoon, Microsporidium, Nosema, Bleistophora, Trachipleistophora, and Vittaforma. Although these infections are found primarily in the compromised host, there is documented evidence that immunocompetent hosts can also become infected. Classification criteria include spore size, configuration of the nuclei within the spores and developing forms, the number of polar tubule coils within the spore, and the relationship between the organism and host cell. The life cycle includes merogony (repeated divisions), schizogony (multiple fission), and sporogony (spore production).

With Enterocytozoon and Encephalitozoon, two of the genera of microsporidia that can infect humans, spore stages in the life cycle are passed in the stool or urine in. a disseminated infection. Within the past few years, diagnostic methods have become available for the identification of microsporidial spores in stool specimens.

However, considering the spore size (approximately 1 to 4 jim), the clinical laboratory may have to wait until immunoassays for antigen or organism detection are available commercially for spore detection. These two genera cause chronic intractable diarrhea accompanied by fever, malaise, and weight loss; dissemination to other body sites such as the kidneys can also occur and is primarily seen in infections with Encephalitozoon spp.

Modified trichrome stains are recommended and should be used with concentrated stool sediment, urine, or other body site specimens (Figure 49-47). Routine histologic stains can also be used on tissues and include Giemsa, trichrome, tissue Gram stains, silver stains, and PAS (Figures 49-48 and 49-49).6

BLOOD PB0T0Z0A Malaria

Malaria is caused by four species of the protozoan genus Plasmodium: P. vivax, P. falciparum, P. ovale, and P. malariae (Table 49-20; see also Tables 49-4 to 49-7) (Figures 4950 to 49-52). The life cycle can be seen in Figure 49-51. Humans become infected when the sporozoites are introduced into the blood from the salivary secretion of the infected mosquito when the mosquito takes a blood meal. These sporozoites then enter the parenchymal cells of the liver, where they undergo asexual multiplication, called the preerythrocytic cycle. Timing of this cycle depends on the species; however, the schi-zonts eventually rupture, releasing thousands of mero-zoites into the bloodstream, where they invade the erythrocytes (red blood cells [RBCs]), called the eryth-

Spores

10 p.m p0iar filament

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Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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