Tags: Cellulitis

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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Borrelia & Leptospira Species

BORRELIA SPECIES RELAPSING FEVER Essentials of Diagnosis The most common presentation is fever with rash, headache, shaking chills, myalgias, arthralgias, and — during the acute phase — hepatosplenomegaly. Louse-borne relapsing fever (LBRF) is epidemic, caused by B. recurrentis, and characterized by one or two relapses. Tick-borne relapsing fever (TBRF) is endemic, caused by several Borrelia species, and characterized by multiple clinical relapses. Organisms can be visualized in blood smears of febrile patients, unlike other spirochetal pathogens, using dark-field microscopy or Giemsa or Wright stains. Helical (3-10 spirals) spirochetes, 8-30 um × 0.3 um, motile (flagella). Weil-Felix reaction: Proteus OX-K agglutinin titers are elevated (this is more common in LBRF). General Considerations …

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Actinomycetes

Actinomycetes are variably acid-fast, gram-positive bacilli that are sometimes filamentous and branched. Originally thought to be fungi due to their hyphae-like appearance, they are now recognized as bacteria based on their cell wall components, reproduction by fission without sporulation or budding, inhibition by antibacterial agents, and molecular phylogenetic analysis. The actinomycete chromosomes contain a high content of guanosine and cytosine. The actinomycetes include the genera Mycobacterium and Corynebacterium, which are discussed in site and site, respectively. The actinomycetes also include the genera Nocardia, Actinomyces, Rhodococcus, Tsukumurella, Gordona, Actinomadura, and Streptomyces, as well as the Whipple’s disease bacillus Tropheryma whippelii. Of these, members of the genus Nocardia are the most significant from …

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Nocardia

Essentials of Diagnosis Gram-positive, variably acid-fast, branching filaments with aerial hyphae. Colonies have characteristic chalky-white or cotton ball appearance. Suspect when chronic pulmonary disease is accompanied by CNS or skin lesions. No specific antibody or antigen detection tests. General Considerations A. Epidemiology. Nocardia spp. are strictly aerobic, ubiquitous soil-dwelling organisms that are largely responsible for the decomposition of organic plant material. Infection usually occurs via inhalation of these organisms in airborne dust particles, leading to pulmonary disease. However, infection can also be acquired via direct percutaneous inoculation by thorns, animal scratches, bites, surgical wounds, and intravenous catheters. Dissemination commonly occurs to the central nervous system (CNS), skin, and subcutaneous tissues. Nocardiosis …

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Yersiniosis

Essentials of Diagnosis • Suspected in a child living in or traveling from a high-prevalence area who has fever, abdominal pain, and diarrhea followed by a reactive polyarthritis. • Yersinia spp. are recovered from cultures of specimens of stool, mesenteric lymph nodes, blood, or abscess material. • Inoculation of duplicate sets of cultures for incubation at 37 and 25 °C, respectively, enhances recovery of the microorganisms. General Considerations A. Epidemiology. Conditions that are associated with increased risk for Yersinia spp. infections (yersiniosis) include iron overload states (such as in patients who receive chronic blood transfusions or those with hemochromatosis) and the use of desferrioxamine, a bacterial siderophore. Infections caused by Y …

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Important Anaerobes

Essentials of Diagnosis • Foul odor of draining purulence. • Presence of gas in tissues. • No organism growth on aerobic culture media. • Infection localized in the proximity of mucosal surface. • Presence of septic thrombophlebitis. • Tissue necrosis and abscess formation. • Association with malignancies (especially intestinal). • Mixed organism morphologies on Gram stain. General Considerations A. Epidemiology and Ecology. Anaerobic bacteria are the predominant component of the normal microbial flora of the human body. The following sites harbor the vast majority of them: • Skin: Mostly gram-positive bacilli such as Propionibacterium acnes • Gastrointestinal tract: In the oral cavity Prevotella spp., Porphyromonas spp., Peptostreptococcus spp., microaerophillic streptococci, and …

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Important Anaerobes: Clinical Syndromes

Box 1 summarizes different clinical syndromes associated with anaerobic bacteria. The sections that follow describe the various syndromes, including clinical findings. For some syndromes, specific diagnosis and treatment information is included as well. For other syndromes, see summary diagnosis and treatment sections at the end of the chapter. HEAD & NECK 1. EAR & PARANASAL SINUSES The flora in as many as two-thirds of chronic sinusitis and otitis cases includes B fragilis, Prevotella spp., Peptostreptococcus spp., and Porphyromonas spp. It is not surprising that ~50% of patients with chronic otitis media are infected with anaerobic bacteria, B fragilis being the most common. Mastoiditis may arise as a complication in some of …

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Legionella

Essentials of Diagnosis • Key signs and symptoms may include minimally productive cough, low-grade fever, headache, and altered mental status. • Risk factors include smoking, advanced age, history of cardiac or pulmonary disease, male gender, and cell-mediated immune suppression. • Common infections include pneumonia with multisystem involvement (Legionnaires’ disease) and nonspecific febrile illness without pulmonary involvement (Pontiac fever). • Gram stain of respiratory secretions may reveal numerous neutrophils without evident organisms. • Aerobic, pleomorphic, faintly staining gram-negative rods are non-spore forming and unencapsulated. General Considerations A. Epidemiology. More than 25 species and 48 serogroups of Legionella have been identified. Legionella pneumophila (especially serogroup 1) causes ~ 70-80% of cases of legionellosis, …

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Legionella: Clinical Syndromes

Legionella species are associated with outbreaks of either Pontiac fever, a self-limited influenzalike condition in otherwise healthy people, or Legionnaires’ disease, a severe pneumonic disease more common among elderly and immunocompromised individuals (Box 1). The spectrum of illness is much broader than these two clinical entities suggest, ranging from completely asymptomatic infection to fulminant respiratory failure and death. 1. PONTIAC FEVER In 1968, the first documented outbreak of Pontiac fever syndrome affected people in a health department building in Pontiac, Michigan. Epidemiologic investigation demonstrated that the infection was airborne and implicated water aerosols that were produced by a faulty air conditioning system as the source of exposure. Sentinel guinea pigs exposed …

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Vibrio & Campylobacter

VIBRIO INFECTIONS VIBRIO CHOLERAE INFECTIONS Essentials of Diagnosis • History of exposure, particularly travel to endemic or epidemic locales. • Acute onset of voluminous, watery diarrhea, with low-grade fever and mild abdominal pain, which are disproportionate to the amount of diarrhea. • During outbreaks, the presence of straight-to-curved gram-negative bacilli, with a single polar flagellum, in the stool of infected patients. • In wet preparations, these organisms demonstrate a characteristic darting or “shooting star” motility. The identification may be confirmed by motility inhibition with specific antisera. • Cultures of V cholerae from stool with differential media, such as thiosulfate-citrate-bile salts-sucrose (TCBS) medium. • Bacterial growth in nutrient broth, without 1% NaCl …

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