Online microbiology notes by SAGAR ARYAL
Structure of Human Astrovirus Human astrovirus falls under Astroviridae and genus Mamastrovirus. The particles are round in shape, 28 nm in diameter with a smooth margin and display a five or six pointed star motif on their surface.The term astrovirus (Greek: astron- star) was coined to refer this feature. They are non-enveloped, spherical, capsid of about … Read moreHuman Astrovirus
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 … Read moreLaboratory Diagnosis, Treatment and Prevention of Francisella tularensis
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 … Read moreLaboratory diagnosis of Legionella pneumophila
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 … Read moreLaboratory diagnosis of Leprosy caused by Mycobacterium leprae
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 … Read moreLaboratory diagnosis, Treatment and Prevention of Mycoplasma pneumoniae
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 … Read moreLaboratory diagnosis, Treatment and Prevention of Streptococcus pneumoniae
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 … Read moreLaboratory diagnosis, treatment and prevention of Leptospira interrogans
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 … Read moreLaboratory diagnosis, treatment and prevention of Borrelia burgdorferi
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 … Read moreLaboratory diagnosis, treatment and prevention of Rickettsia rickettsii
Laboratory diagnosis of Corynebacterium diphtheriae Specimen Dacron swabs from the nose, throat, or other suspected lesions must be obtained before antimicrobial drugs are administered. Swabs should be collected from beneath any visible membrane. The swab should then be placed in semisolid transport media such as Amies. Microscopy Smears stained with alkaline methylene blue or Gram stain … Read moreLaboratory diagnosis, treatment and prevention of Corynebacterium diphtheriae