Tiêu đề 20. MICROBIOLOGICAL ASSAY OF PENICILLIN, STREPTOMYCIN.pdf ✅

PHARMD GURU Page 1  Penicillin, Streptomycin are belongs to antibiotic class. MICROBIOLOGICAL ASSAY OF PENICILLIN, STREPTOMYCIN: The microbiological assay of an antibiotic is based upon “comparison of the inhibition of growth of microorganisms by measured concentrations of the antibiotics under examination with that produced by known concentrations of a standard preparation of the antibiotic having a known activity”. Two general methods are usually employed: 1) The cylinder-plate (or cup-plate) method. 2) The turbidimetric (or tube assay) method. THE CYLINDER-PLATE (OR CUP-PLATE) METHOD: The cylinder-plate method depends upon diffusion of the antibiotic from a vertical cylinder through a solidified agar layer in a petri dish or plate to an extent such that growth of the added micro-organism is prevented entirely in a zone around the cylinder containing a solution of the antibiotic. THE TURBIDIMETRIC METHOD: The turbidimetric method depends upon the inhibition of growth of a microbial culture in a uniform solution of the antibiotic in a fluid medium that is favorable to its rapid growth in the absence of the antibiotic. PREPARATION OF STOCK SOLUTION:  To prepare a stock solution, a quantity of the standard preparation of a given antibiotic is accurately weighed and dissolved in the solvent specified and then diluted to the required concentration as indicated.  The solution to be stored in a refrigerator and used within the period of time.  On the day of assay, from the stock solution five or more test dilutions, the successive solutions increasing stepwise in concentration, usually in the ratio 1:1.25 are prepared for cup plate method or in smaller ratio for tube assay. MICROBIOLOGICAL ASSAY OF PENICILLIN, STREPTOMYCIN
PHARMD GURU Page 2  Use the final diluents specified and a sequence such that the middle or median has the concentration specified. TEST MICROORGANISM: The test organism for each antibiotic is listed together with its identification number in the American Type Culture Collection (ATCC). The culture is maintained on slants of the medium and under the incubation conditions specified and transferred weekly to fresh slants. Ex: Penicillin (antibiotic) - Staphylococcus aureus (test organism) - 29737 (ATCC No), Streptomycin - Klebsiella pneumoniae - 10031.  The media required for the preparation of test organism inocula is prepared from the ingredients.  Minor modifications of the Individual Ingredients may be made, or reconstituted dehydrated media may be used provided the resulting media have equal or better growth-promoting properties and give a similar standard curve response.  The ingredients are dissolved in sufficient water to produce 1000 ml and sufficient 1M sodium hydroxide or 1 M hydrochloric acid is added as required to adjust the pH. TURBIDIMETRIC METHOD:  A method has been developed for turbidimetric measurement of bacterial growth in standard inexpensive test tubes with closures in-place.  Liquid cultures and agar plug diffusion cultures can be assayed using an unmodified spectrophotometer.  Growth curves of replicate cultures grown in test tubes are reproducible with respect to similarity of curve shape, onset of logarithmic growth phase, and maximum growth. ADDITIONAL INFORMATION:
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