Tags: Meningitis

Cysticercosis (Cysticercus Cellulosea Infection)

Essentials of Diagnosis • Surgical excision of involved tissue, with microscopic identification of parasite. • Frequently calcified cysts present on x-ray or computed tomography (CT) scans. • Positive serology indicating previous exposure to T solium. • Fine-needle aspiration of cysts (characteristic cytomorphology). General Considerations Cysticercosis is caused by invasion of tissue by the larval forms of T solium, which have been referred to as Cysticercus cellulosea, although the name is not taxonomically correct and introduces confusion. Within a host infected by the adult T solium, eggs or proglottids are passed in the stool. Once eggs or proglottids are ingested by either pigs (intermediate hosts) or humans (definitive and intermediate hosts), eggs …

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Nematodes

Essentials of Diagnosis Intestinal nematodes: demonstration of characteristic eggs or parasites in stool. Bloodstream nematodes (filariasis): clinical diagnosis can be made; fresh blood smear may be confirmatory. Tissue nematodes: clinical diagnosis can be made; skin snip or other tissue examination may show organism. General Considerations Nematodes (roundworms) are nonsegmented, tapered, bilaterally symmetrical, cylindrical organisms that have complete digestive tracts and reproduce sexually. Although > 500,000 species of nematodes have been described, only a small number are commonly encountered as human parasites. Most nematodes have complex life cycles, sometimes involving several larval forms and intermediate hosts or free-living stages. The pathogenic nematodes may be categorized as primarily intestinal or extraintestinal tissue parasites …

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Intestinal Nematode Infections

ASCARIASIS Worldwide, more than 1 billion people are infested with Ascaris lumbricoides, the causative agent of ascariasis or roundworm. More than 4 million people are estimated to be infected in the United States. Infection occurs predominately in the southeastern states and more commonly in younger children, and it is associated with lower socioeconomic status. The organism is acquired through ingestion of embryonic forms of the worm, which are found in fecally contaminated soil. After ingestion, the embryonic eggs hatch in the small intestine, and the larvae undergo a tissue migration phase. During the migration, the larvae penetrate the intestinal wall and travel intravenously to the pulmonary alveoli. In the lungs, the …

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Non-falciparum Malaria (P Vivax, P Ovale, P Malariae)

Clinical Findings A. Signs and Symptoms. Patients with nonfalciparum malaria invariably develop fever and chills that may become cyclic. Initially, patients experience chills, which are followed by fever (Box 1). Patients with malaria often manifest many nonspecific symptoms such as weakness, malaise, headache, and myalgias. As the disease progresses, signs of anemia, such as pale conjunctiva, may be seen. Splenomegaly and mild hepatomegaly may also be present. After hours of fever, defervescence occurs with marked diaphoresis. Patients are weakened and exhausted from the severity of the disease. In established infections caused by P vivax and P ovale, a periodicity may occur approximately every 48 h. P vivax and P ovale infections …

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Sporothrix Schenckii

Essentials of Diagnosis Cigar-shaped yeast. Dimorphic: mycelial in nature, yeast in tissue. Associated with activities that involve contact with soil, sphagnum moss, decaying wood, or vegetation. Gardeners, forestry workers, miners, animal health care providers most at risk. Raised skin lesions with proximal spread along lymphatic channels. Recovery of microorganism from culture. General Considerations A. Epidemiology. Sporothrix schenckii, the causative agent of sporotrichosis, is a ubiquitous fungus commonly found in the soil, on sphagnum moss, on decaying wood, and on a variety of other vegetation. It is found worldwide but prefers a temperate or tropical climate with high humidity. Most cases of sporotrichosis are sporadic, but large human epidemics have been reported. …

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Cryptococcus Neoformans

Essentials of Diagnosis Routine laboratory tests often normal. One-third of patients are afebrile. Definitive diagnosis made by fungal culture maintained at 37°C for 6 weeks. Cryptococcal antigen 95% sensitive in CNS infection in centrifuged CSF. India ink examination positive in only 50% of meningoencephalitis cases. CSF lymphocytes often low in CNS infection, especially in AIDS patients. Cryptococcal antigen most sensitive detection method in serum. Chest radiograph variable — multiple areas of infiltration in lower lobes most common in pulmonary disease. Molecular detection by PCR might soon become laboratory standard. General Considerations A. Epidemiology and Ecology. Cryptococcus neoformans exists as two distinct varieties known as variety neoformans and variety gattii (Table 1). …

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Candida Species

Essentials of Diagnosis Characteristic appearance of yeast and hyphae on KOH preparations. Formation of germ tubes in serum is presumptive diagnosis for Candida albicans. Cultures must be interpreted with caution because positive culture may represent colonization rather than infection. Serology not useful. General Considerations A. Epidemiology. Candida organisms are commensal with humans and, in the absence of alterations in host defense mechanisms, usually do not cause disease. Candida exists as normal flora within the oral cavity, throughout the gastrointestinal (GI) tract, in expectorated sputum, in the vagina, and in the bladder of patients with indwelling catheters. There are >150 species within the genus Candida, although the majority are not known to …

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Coccidioides

Essentials of Diagnosis Predisposing factors include travel to the dry desert climates found in the southwestern United States and exposure to dust. The commonest source of infection is dust inhalation in the southwestern United States. The commonest infection is pneumonia. Key laboratory findings include growth of the fungus and complement fixing (CF) antigen detection by immunodiffusion. General Considerations Coccidioidomycosis was first described as a disease a little more than a century ago in Buenos Aires, Argentina. It was in San Francisco that the organism causing the clinical disease was given its name, Coccidioides immitis. Many diseases were later found to be caused by this organism, including San Joaquin Valley Fever. A. …

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Blastomyces Dermatitidis (Blastomycosis)

Essentials of Diagnosis Round thick-walled yeast with broad-based budding. Dimorphic: mycelial in nature, yeast in tissue. Associated with activities in proximity to waterways. Associated with exposure to dust, eg excavation. Endemic in states surrounding the Mississippi and Ohio Rivers. Pyogranulomas on histopathological examination. Acute or chronic infection of lung, skin, bone, or genitourinary tract. Recovery of microorganism from culture of tissue. General Considerations A. Epidemiology. Blastomyces dermatitidis is an endemic fungus that causes acute and chronic infections in humans and other animals. It is found primarily in the south central, southeastern, and midwestern United States, especially in the states surrounding the Mississippi and Ohio Rivers. Outside the United States, cases have …

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Histoplasma Capsulatum

Essentials of Diagnosis Thin-walled oval yeast measuring 2-4 mm in diameter. Dimorphic: mycelial in nature, yeast in tissue. Endemic within Ohio and Mississippi River Valleys. Associated with activities that disturb dust or soil enriched with bird, chicken, and bat excrement. Complement fixation antibody titer 1:32 or greater. Simultaneous appearance of anti-H and anti-M antibodies. Infection most often is asymptomatic or may cause chronic pulmonary infection; less commonly, disseminated infection involving the adrenals, ulcerative gastroenteritis lesions, or central nervous system. Recovery of organism from culture of tissue, blood, sputum, or other source. General Considerations A. Epidemiology. Histoplasma capsulatum, the etiologic agent of histoplasmosis, is an endemic, dimorphic fungus that causes a wide …

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