Tags: Tuberculosis

Leishmania

Leishmania & Trypanosoma The genera Leishmania and Trypanosoma are members of the family Trypanosomatidae. These protozoans cause diseases with widely varied clinical presentations as well as geographic distributions, including leishmaniasis, American trypanosomiasis (Chagas’ disease), and African trypanosomiasis (sleeping sickness). For example, the endemic zones for African and American trypanosomiasis do not overlap, the diseases are transmitted by different vectors, they involve distinct mechanisms of pathogenesis, and they follow different clinical courses. Nonetheless, the causative agents share important biological features. Each is a hemoflagellate with a kinetoplast containing its own chromosomal DNA with highly conserved and repeated elements, each forms a single flagellum at some point during its life cycle, and each …

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Toxoplasma Gondii

General Considerations A. Epidemiology. Toxoplasma gondii infection, or toxoplasmosis, is a zoonosis (the definitive hosts are members of the cat family). The two most common routes of infection in humans are by oral ingestion of the parasite and by transplacental (congenital) transmission to the fetus. Ingestion of undercooked or raw meat that contains cysts or of water or food contaminated with oocysts results in acute infection. In humans, the prevalence of toxoplasmosis increases with age. There are also considerable geographic differences in prevalence rates (eg, 10% in Palo Alto, CA; 15% in Boston, MA; 30% in Birmingham, AL; 70% in France; = 90% in El Salvador). Differences in the epidemiology of …

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Chromomycosis

Essentials of Diagnosis • Patients are usually immunocompetent. • Found worldwide but usually in tropical or subtropical areas. • Mold in culture; forms sclerotic body or muriform cell in tissue. • Infection results from direct inoculation from contaminated soil or vegetative substances. • Chronic indolent cutaneous verrucous lesions, most often on the feet. General Considerations Chromomycosis, also known as chromoblastomycosis, is a chronic subcutaneous infection caused by several different fungi. Although rarely seen in the United States, it is common worldwide. A. Epidemiology. Chromomycosis occurs worldwide but is most frequently encountered in tropical and subtropical regions. The most common occurrence is in barefoot individuals, particularly among agricultural workers. The organisms causing …

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Paracoccidioidomycosis

Essentials of Diagnosis • Patients usually immunocompetent. • Patients in endemic areas with chronic pulmonary and mucotaneous lesions involving the mouth, nose, larynx, and face; regional or diffuse lymphadenopathy. • Found in Latin America, from Mexico to Argentina. • Dimorphic fungus: yeast form in tissue specimens and at 37 °C; mold form when grown at room temperature in the laboratory. • Thick-walled yeast, 4-40 um, with multiple buds when seen in tissue specimens. • Complement fixation or immunodiffusion. General Considerations Paracoccidioidomycosis is caused by Paracoccidioides brasiliensis. Also known as South American blastomycosis, it is the most prevalent systemic mycosis found in Central and South America and is the most common endemic …

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Penicillium Infections

Essentials of Diagnosis • Penicillium marneffei infection found in both immunocompetent and immunosuppressed patients. • P marneffei found in Southeast Asia and southern China. • Mold, septate hyphae 1.5-5 um in diameter. • May be cultured from a variety of specimens including blood. • Penicillium spp. other than P marneffei occur worldwide. • Infection with Penicillium spp. is rare; occurs in immunosuppressed patients. General Considerations A. Epidemiology. Penicillium spp. are ubiquitous in nature and may be recovered with ease from a variety of sources within the hospital environment. These molds commonly contaminate clinical specimens and cause contamination in the laboratory. Colonization of nonsterile anatomical sites in humans is common. In most …

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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 …

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Aspergilloma

An aspergilloma of the lung may develop in individuals who have preexisting cavitary lung disease caused by conditions such as tuberculosis, sarcoidosis, silicosis, or bronchiectasis. Also known as a fungus ball or mycetoma, aspergillomas can be regarded as heavy Aspergillus colonization of the preexisting cavity. Clinical Findings A. Signs and Symptoms. The most common symptom is hemoptysis, and, on rare occasions, severe or fatal hemoptysis can develop. Other symptoms are usually related to the underlying lung disease. B. Laboratory Findings. Patients with an aspergilloma of the lung typically have elevated IgG levels specific for Aspergillus spp. Sputum smear may show the presence of filamentous fungi, and culture is intermittently positive for …

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Blastomyces Dermatitidis

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 …

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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 …

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Bartonella

Essentials of Diagnosis • Key signs and symptoms include dermal lesion (bacillary angiomatosis and chronic phase of Bartonella bacilliformis infection); papule at inoculation site followed by proximal lymphadenopathy (cat scratch disease); fever, bacteremia, acute hemolytic anemia (acute phase of B bacilliformis infection); persistent or relapsing fever (fever and bacteremia/endocarditis). • Predisposing factors include louse exposure, low income, and homelessness (Bartonella quintana-associated bacillary angiomatosis, fever, and bacteremia/endocarditis); cat exposure (cat scratch disease and Bartonella henselae-associated bacillary angiomatosis, fever and bacteremia/endocarditis); sandfly exposure in endemic areas of South American Andes (B bacilliformis infection). • History of HIV or immunocompromise (bacillary angiomatosis). • Key laboratory findings include small, curved, pleomorphic weakly gram-negative bacilli, best …

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