Online Microbiology and Biology Notes
Disease Control Control of communicable diseases, which implies reducing their occurrence, has always been a major public health priority. In the past, control measures were based on incomplete knowledge of the epidemiology of the disease to be controlled and were directed at perceived factors of disease causation. As knowledge of the epidemiology of diseases improved, and with the development of …
Neisseria gonorrhoeae is an obligate human pathogen and is the etiological agent of gonorrhea. In the United States, it is the second most commonly reported communicable disease, with more than 350,000 cases reported annually. Syndromes include cervicitis in women and urethritis, pharyngitis and proctitis in both sexes. If untreated, women may experience severe sequelae of pelvic inflammatory disease, chronic pelvic …
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Laboratory diagnosis of Francisella tularensis Specimen Scrapings from infected ulcers, lymph node biopsies, and sputum, whole blood. Serum is generally collected from all patients early in disease and during convalescence. To minimize the loss of viable organisms, samples should be transported to the laboratory within 24 hours. If specimens are to be held longer than 24 hours, specimens should be …
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Laboratory diagnosis of Legionella pneumophila Specimen: Respiratory secretions (sputum, bronchial aspirate or washings), as well as pleural fluid, lung biopsy or autopsy material. Microscopy Legionellae in clinical specimens stain poorly with Gram stain and the small, intracellular bacteria are rarely recognized. The organism will stain with nonspecific methods, such as Dieterle silver stain, but this stain is used with tissue …
Laboratory diagnosis of Leprosy caused by Mycobacterium leprae Specimen Skin biopsies, nasal discharges, scrapings from the nasal mucosa and slit-skin smears which are prepared by making superficial incisions in the skin, scraping out some tissue fluid and cells. Skin smears The skin smears are collected from the leprous lesions, such as nodules, thick papules, and areas of infiltration. In cases …
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Laboratory diagnosis of Mycoplasma pneumoniae Specimen Ideal specimens are throat swabs and nasopharyngeal aspirates, lung biopsies, expectorated sputum. Washings are more reliable than sputum specimens because most infected patients have a dry, nonproductive cough and do not produce sputum. Microscopy Test is not useful because organisms do not have a cell wall and do not stain with conventional reagents Culture …
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Laboratory diagnosis of Streptococcus pneumoniae Specimen: Sputum, blood, endotracheal aspirate, bronchoalveolar lavage, cerebrospinal fluid (CSF), pleural fluid, joint fluid, abscess fluid, bones, and other biopsy material. Microscopy Gram staining of sputum shows lancet shaped Gram-positive cocci in pairs. Fresh emulsified sputum mixed with antiserum causes capsule swelling (the quellung reaction) for identification of pneumococci. In acute pneumococcal otitis media, Gram …
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Laboratory diagnosis of Leptospira interrogans Specimens Specimens consist of aseptically collected blood in a heparin tube, CSF, urine, or tissues for microscopic examination and culture. Serum is collected for agglutination tests. Microscopy As leptospires are thin, they are at the limit of the resolving power of a light microscope and thus cannot be seen by conventional light microscopy. It cannot …
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Laboratory diagnosis of Borrelia burgdorferi Specimen Blood, cerebrospinal fluid, joint fluid, tissue biopsies Body fluids should be transported without any preservatives. Tissue biopsy specimens should be placed in sterile saline to prevent drying. Direct detection methods The organisms can be seen directly in wet preparations of peripheral blood (mixed with equal parts of sterile, non bacteriostatic saline) under dark- or …
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Laboratory diagnosis of Rickettsia rickettsii Specimen: Skin biopsies, serum Direct detection method Although Rickettsiae stain poorly with Gram stain, they can be stained with Giemsa or Gimenez stains. Direct detection of R. rickettsii antigen in skin biopsy specimens of the rash from infected patients by direct fluorescent antibody test using the specific anti-rickettsial antibodies is a rapid and specific method for confirming …
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