Bacterial Identification Flashcards
Name the gold-standard data set listing classified bacterial characteristics, noting which ones are present or absent in certain organisms.
Bergey’s Manual of Determinative Bacteriology
How is the accumulated Bergey’s data used to identify unknown bacteria?
The data are used to create a dichotomous key strategy.
What are the three main data points to note in unknown identification of bacteria?
- microscopic appearances,
- characteristics of the bacteria in culture, and
- physiologic or biochemical testing results.
Describe a dichotomous key.
a flowchart that can be used to identify an organism by making a series of choices until you arrive at one possibility.
To best identify a specific bacterial species, what should be done first? (This step was done for you in the labs.)
it should be isolated away from other contaminating organisms into a pure culture
What are four key parts to the techniques for identifying unknown bacteria?
- Staining the unknown for initial characterization by microscopy.
- Using a dichotomous key strategy to systematically rule out other organisms.
- Testing the organism for key biochemical traits.
- Accumulating data and characteristics of the unknown until a positive identification can be made.
What is the most common initial test of unknown identification?
Gram staining is the most common initial test of unknown identification, as
* it separates organisms into two broad classes, gram-positive and gram-negative, based on the cell wall structure.
* It also shows the size, shape, and arrangement of bacterial cells, which is helpful in further characterizing the identity of the unknown organism.
After quick-characterization by staining, what tests typically come next?
specialized growth media can be used to indicate further biochemical characteristics of an unknown organism.
These tests use visual outcomes, such as colors, patterns, and changes in appearance. The results can be interpreted to then assign a characteristic to the unknown organism.
Specialized growth media tests
Regarding bacterial identification, describe biochemical testing.
Tests used in the identification of bacterial species. Because of the inherent differences in physiologic and metabolic activities of bacterial species, biochemical testing reactions can help provide presumptive identification of isolates based on the presence or absence of a trait.
List some examples of biochemical testing.
Examples include catalase, oxidase, sugar fermentation, hemolysis, and enzymatic activity.
Regarding bacterial identification, describe genetic characteristics.
Genetic characterization refers to the analysis of bacterial DNA sequence for unique orders that are found in only one organism. This method is highly sensitive but subject to contamination and errors.
Regarding bacterial identification, describe Immunologic characteristics.
Immunological characterization refers to the identification of an unknown organism by antibody binding assays. This method is rapid and specific, but subject to false positives and negatives, as well as relying on the immune activity of the patient or sample.
Regarding bacterial identification, describe Phenotypic characteristics.
Phenotypic characterization includes observing bacterial morphology, staining properties, and biochemical testing results. These are done visually, noting the appearance, color, etc., of a test.
