[Rapid diagnosis of infectious diseases; features and limitations of the microscopic examination of clinical specimens].
The diagnosis of infectious diseases relies on the microbiological examinations. The microscopic examination of clinical specimens has been well known as one of the rapid methods in diagnostic microbiology. The reasons for the microscopic examination in the clinical microbiology are emphasized and summarized as the following features and limitations: ADVANTAGES OF MICROSCOPY. The use of a stained smear microscopy by Gram, Ziehl-Neelsen and fluorochrome stains still remains the most available, easy to perform, and inexpensive. This technique can be done routinely in a variety of clinical settings. The direct microscopy provides judging specimen quality, detecting a variety of organisms in clinical specimens, and evaluating the type of inflammatory response. Typical Gram reactions, morphologies and arrangements of the observed organisms may give the presumptive identification of some certain etiological bacteria, yeasts or fungi, and significant of the organisms. The observing organisms and those forms may also guide to the laboratory in selecting appropriate isolation media and culture methods, and aid to the physician in selecting an empirical antibiotic therapy. DISADVANTAGES AND LIMITATIONS OF MICROSCOPY. The microscopy of clinical specimen is much less sensitive than the culture method for detection of small numbers of bacteria. A specimen usually contains 10(4) to 10(5) or more organisms per milliliter before it is likely that organisms will be seen on a smear. The appearance of bacteria on Gram-stained smears does not permit the identification of species. FACTORS AFFECTING TO RESULT OF MICROSCOPIC EXAMINATION. A number of factors may affect the result of the microscopic examinations. Specimen quality, clinical presentations of the patients, presence of the various cellular components in the background of smear, bacteriological statistics, and individuals in the microbiology laboratory are responsible to the reliability and quality of the results. The concordance between results obtained from a microscopy and from further tests may also provide sufficient information to presumptive identification and diagnosis. Laboratory observers, whom should have abundant experiences and receive sufficient training, are requiring for control and quality of the examination.
Misawa
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Clinical Laboratory, Jutendo University Hospital, Hongo, Bunkyo-ku, Tokyo, Japan
D001419:Bacteria / Q000302:isolation & purification; D001431:Bacteriological Techniques; D019411:Clinical Laboratory Techniques; D006801:Humans; D007239:Infections / Q000382:microbiology*; D016920:Meningitis, Bacterial / Q000382:microbiology; D008853:Microscopy