BioAssay of Antibiotics 1973 PDF

Bioassay of Antibiotics  Bioassay of Antibiotics  The potency of a sample of antibiotic is determined by comparing the dose which inhibits the growth of a suitable susceptible micro organism with the dose of standard preparation of that antibiotic which produces the...

Bioassay of Antibiotics  Bioassay of Antibiotics  The potency of a sample of antibiotic is determined by comparing the dose which inhibits the growth of a suitable susceptible micro organism with the dose of standard preparation of that antibiotic which produces the same degree of inhibition.  Standard preparation and unit  The standard preparations are supplied as dry powders in sealed ampoules containing the approximate quantity as given in the monographs.  The potency of an antibiotics is usually described as Units contained in 1mg of the powder or mg containing in 1 Units.  Eg: 641 units of gentamicin sulphate is contained in 1 mg or 0.00156 mg contain 1 Unit.  Procedure for Biological assay of Streptomycin  Take washed, dried and clean petri dishes / recangular trays.  Prepare nutrient agar medium.  Filled the petri dishes to a depth of 3-4mm  Inoculate with 1% v/v of suitable inoculum of Bacillus subtilis.  During inoculation temp: of medium must not exceed 48c-50c.  The layers of the medium must be of uniform thickness in dishes or trays.  After inoculation keep the petri dishes at 37c for 1-2 minutes. Then allow the petri dishes to dry for 30 minutes at room temp: or solidify by storage in refrigerator.  Take small sterile cylinders of uniform size, approximately 10mm high, having an internal diameter of 5mm.  The cylinders are made up of glass, porcelain, aluminum or stainless steel which are maintain at 150C temp:  Place the cylinders on the surface of the inoculated medium.  4,6or 8 cylinders or any other number which can be conveniently adjusted to the size of the petri dishes.  If cylinders are not possible due to any reason then holes of 5-8mm in diameter may be bored in the medium through sterile borer.  Prepare the standard solution of known concentration and test solution in a sterile solution having pH 8.  The solutions are placed in holes or cylinders by means of pipette which delivers uniform amount of solution sufficient to fill up the holes.  Mark the test solution and standard solution with proper coding.  Then keep the petri dishes at room temp: for 2-4 hours.  The petri dishes are then incubated at suitable temp: for 16 hours.  The diameter of the zone of inhibition produced by various concentration of test and standard preparations measured with greater accuracy.  From the results potency is calculated by referring Pakistan pharmacopeia 1973.