MCQ Microbiology Culture Techniques

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Microbiology Culture Techniques 1. Streaking 2. Plating 3. Dilution 4. Enriched procedure, and 5. Single cell technique.

1. Streaking: This is most generally used method of isolation. The technique consists of pouring an appropriate sterile medium into sterile petriplate and allowing the medium to solidify. By means of a sterile loope or straight needle or a sterile bent glass-rod alittle amount of growth preferably from a broth culture or bacterial suspension is streaked back and forth across the surface of agar until about one third of the diameter of the plate has been covered. The needle is then flamed and streaking in done at right angles to and across the primary streak. This serves to tug bacteria call at an extended line from the initial streak. When this streaking is completed the needle is again flamed and streaking is completed at right angles to the second streak and parallel to the primary .

2. Plating: It includes diluting of a mix of microorganisms until only a couple of hundred bacteria are left in each millilitre of the suspension. a really bit of the dilution is then placed during a sterile petriplateby means of a sterile loop or pipette. The melted agar medium is cooled to about 45°C and is poured into plate. The microorganism and agar are well mixed. When the agar is solidified the individual bacterium are going to be held in situ and can grow to a clear colony.

3. Dilution: This method is employed for the microorganisms which can’t be easily isolated by streaking or plating method. Sometimes when several organisms are present during a mixture, with one organism predominating, the predominating form could also be isolated by this method. for instance , when milk is allowed to sour at temperature it’ll , at the time of curding, have a mix of microorganisms with high percentage of Streptococcus lactis. If 1 ml of the sour milk is taken into a tube containing 9 ml. of sterile milk (in which no organisms are present) then 1 ml. of this mixture is transferred with a sterile pipette into a second tube of sterile milk and therefore the procedure is repeated i.e. from second to 3rd tube, third to fourth tube until a series of about 10 tubes are inoculated. By this serial dilution, the probabilities are that a pure culture of S. lactis are going to be obtained.

4. Enrichment Procedure: This procedure involves the utilization of media and conditions of cultivation which favour the expansion of the specified species. for instance , when a person suffers with typhoid, the intestinal discharge posses small number of typhoid bacillus in comparison with E. coli and other forms

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