Microtopic 5E DIAGNOSING INFECTIONS - Microtopic 5E...

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DIAGNOSING INFECTIONS A most pressing topic in Microbiology is how to identify unknown bacteria. The methods used fall into 3 main categories: Phenotypic methods – looking at the morphology and physiology of the microbes. Immunological methods – using serological analysis. Genotypic methods – using genetic techniques. The Phenotypic Methods A listing of characteristics including: 1. Microscopic morphology (size and shape, staining characteristics gram/acid-fast/special structures). 2. Macroscopic morphology (appearance of colonies) 3. Physiological/Biochemical characteristics (types of media they grow in and changes that occur in media exposed to the chemicals they produce) 4. chemical analysis – structural substances they contain Genotypic Methods Examination of the genetic material has become a major method for identification and classification of bacteria (G + C content of DNA and rRNA sequencing). The advantage of genotypic methods over phenotypic methods are that culturing is not always necessary and they are more automated now so the process is faster. Immunological methods These methods utilize the specificity of the antigen-antibody reaction to identify the presence of a microbe in a patient’s serum. They use known antibodies to conduct a number of tests to indicate the presence of an antigen, or they can test the serum for the presence of antibodies using a known antigen (this would indicate patient exposure to the antigen in the past). TRACKING DOWN THE INFECTIOUS AGENT – SPECIMEN COLLECTION The success of identification often depends on how specimens are collected, handled, and stored. Aseptic procedures are used including sterile sample containers to prevent contamination. In sites where normal flora is present care needs to be taken to sample only the infected site and avoid surrounding areas. *** see figure 17.1 in text Routes taken in specimen analysis direct tests – microscope, immunological, or genetic methods cultivation, isolation, and identification (use a variety of general & specific tests). Test result categories:
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This note was uploaded on 06/23/2009 for the course MCB 2023 taught by Professor Thompson during the Summer '09 term at Central Community College.

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Microtopic 5E DIAGNOSING INFECTIONS - Microtopic 5E...

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