Tags: Pneumonia

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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Pneumocystis Carinii

Essentials of Diagnosis Pneumocystis carinii, when examined using molecular techniques, most closely resembles a fungus. Stains of either bronchoalveolar-lavage (BAL) or transbronchial-biopsy samples yield a diagnosis in > 90% of patients and should be considered the gold standard in diagnosis. BAL with transbronchial biopsy increases diagnostic yield to ~ 100%. P carinii has not yet been cultured in vitro. Polymerase chain reaction (PCR) (especially on sputum) increases sensitivity but reduces specificity. The prophylactic use of aerosolized pentamidine reduces the sensitivity of sputum and bronchoscopic samples. General Considerations A. Epidemiology. In 1983, P carinii pneumonia (PCP) was described as the AIDS-defining illness in = 60% of the first 1000 patients diagnosed with …

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Extrapulmonary P Carinii Infections

Extrapulmonary P carinii infections occur in < 3% of patients and must be diagnosed with histopathologic samples. Primary prophylaxis for PCP with pentamidine may confer a higher risk for extrapulmonary infection. Symptoms of extrapulmonary involvement are nonspecific, usually consisting of fevers, chills, and sweats. Although any area of the body may be involved, splenomegaly with cysts and thyroiditis are most common. Diagnosis The practice of diagnosing PCP morphologically by traditional staining methods (silver methenamine and toluidine blue) of induced sputum samples in HIV-infected individuals has fallen out of favor. Although relatively simple and inexpensive, staining of sputum samples induced by hypertonic saline inhalation is clearly dependent on operator and laboratory experience, …

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Aspergillus, Pseudallescheria, & Agents of Mucormycosis

ASPERGILLUS INFECTION Essentials of Diagnosis Filamentous fungus with septate hyphae 3-6 um in diameter. Branching of hyphal elements typically at 45° angle. Specific IgG antibodies generally of no use diagnostically since most patients are immunosuppressed and will not generate antibody response. Pulmonary lesions, localized or cavitary in susceptible host. General Considerations A. Epidemiology. Aspergillus spp. are found worldwide and grow in a variety of conditions. They commonly grow in soil and moist locations and are among the most common molds encountered on spoiled food and decaying vegetation, in compost piles, and in stored hay and grain. Aspergillus spp. often grow in houseplant soil, and such soil may be a source of …

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Pseudallescheria Boydii Infection

Essentials of Diagnosis Filamentous fungus that is morphologically similar to Aspergillus spp. Most serious infections occur in immunosuppressed patients. Recovery from culture must be distinguished from colonization or contamination. General Considerations P boydii is a mold that is capable of causing infection in immunosuppressed patients and less frequently in immunocompetent patients. Overall, infection with P boydii is rare. A. Epidemiology. Although a relatively common environmental mold, P boydii is a rare cause of human disease. It can be easily recovered from soil, water, and manure. Both community and nosocomial acquisition have been documented. In most instances, its recovery from culture specimens will reflect colonization or contamination; however, it is capable of …

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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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