Tags: Osteomyelitis

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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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 …

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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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Mycoplasma & Ureaplasma

Mycoplasma and Ureaplasma species (mycoplasmas) are ubiquitous in nature and are commonly found in plants, animals, and humans. These bacteria contain the smallest amount of double-stranded DNA that is capable of producing a free-living microorganism; they measure between 0.15 and 0.3 um in diameter and = 2 um in length. They are believed to have evolved from a putative common ancestor of the gram-positive bacteria by a process of genome reduction and adoption of a dependent, parasitic life style. Mycoplasma and Ureaplasma spp. lack a cell wall. Therefore, they cannot be visualized with the Gram stain and are not susceptible to antibiotics that act on cell wall synthesis (eg, penicillins and …

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Treponema Pallidum

Essentials of Diagnosis • Spiral, motile, coil-shaped, elongated (0.10 um × 5-20 um) spirochete. • No reliable method for sustained in vitro cultivation. • Direct detection with darkfield microscopy or immunofluorescent antibody in early syphilis. • Nontreponemal antibody tests (rapid plasma reagin, Venereal Disease Research Laboratory [VDRL]) for screening, treatment follow-up. • Treponema-specific antibody tests (fluorescent treponemal antibody test, microhemagglutination-T pallidum test) for confirmation. • Cerebrospinal fluid (CSF) lymphocytosis, elevated CSF protein, or reactive CSF VDRL test suggests neurosyphilis. • PCR, DNA probes, and immunoblotting techniques promising in congenital syphilis, early syphilis, or neurosyphilis. • All patients with T pallidum infection should be tested for HIV coinfection and vice versa. General …

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Actinomyces

Essentials of Diagnosis • “Sulfur granules” in specimens and sinus tract drainage: hard, irregularly shaped, yellow particles measuring from 1 to 5 mm in size • Gram-positive branching filaments arranged in ray-like projections under the microscope • Colonies with characteristic “molar tooth” appearance • Production of extensive fibrosis with “woody” induration • No specific antibody or antigen detection tests General Considerations A. Epidemiology. The Actinomyces species are facultative anaerobes that commonly inhabit the oral cavity, the gastrointestinal tract, and the female genital tract, where they exist as commensals. Diversity within this genus is broad, which has led to taxonomic revision and reclassification of some species as members of the Arcanobacterium genus, …

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Other Mycobacteria

  Essentials of Diagnosis • Demonstration of the acid-fast bacillus. • Infections more common in immunocompromised hosts. • Infections mainly pulmonary or soft tissue. General Considerations The increasingly relative importance of the atypical mycobacteria, many of which are ubiquitous in the environment, was recognized with the decline in tuberculous disease. Generally, atypical mycobacteria are unusual causes of disease in patients who are immunocompetent but can in immunocompromised hosts such as AIDS and cancer patients. Most infections caused by atypical mycobacteria are skin and soft tissue abscesses, sometimes following pulmonary infection or implantation of prosthetic devices. There have been a few reports of epidemics of iatrogenic infection with atypical mycobacteria, associated with …

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Mycobacterium Avium Complex (Disseminated & Pulmonary Disease)

Mavium is the most common atypical mycobacterium to cause disease in humans. In immunocompetent patients, M avium can cause pulmonary disease (Box 1). It is the most common pulmonary pathogen of all the atypical mycobacteria. There are several risk factors for pulmonary M avium infection besides AIDS. Patients with underlying pulmonary disease, those who have had a gastrectomy, and those with cystic fibrosis can develop pulmonary infection. Pulmonary disease can also develop in a subgroup of women without pulmonary disease but with mitral valve prolapse, pectus excavatum, and thoracic scoliosis. In immunocompromised patients such as those with AIDS who have a CD4 lymphocyte count of < 100, M avium can cause …

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Brucella, Francisella, Pasteurella, Yersinia, & Hacek

BRUCELLOSIS Essentials of Diagnosis • Suspected in patients with chronic fever of unknown etiology who have a history of occupational exposure or come from a high prevalence area. • Leukopenia. • Blood culture or bone marrow cultures on appropriate media. • Serum antibody titer = 1:160. • Polymerase chain reaction. General Considerations Brucellosis (also called undulant fever, Mediterranean fever, Malta fever) is an infection that causes abortion in domestic animals. It is caused by one of six species of Brucella coccobacilli. It may occasionally be transmitted to humans, in whom the disease could be acute or chronic with ongoing fever and constitutional symptoms without localized findings. A. Epidemiology. Brucellosis is transmitted …

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