VLD 421: Veterinary Clinical Biochemistry and Laboratory Diagnosis-II (0+1)

PROCEDURE FOR ANTIBIOGRAM

• Keep the required number of MH agar plates , properly labeled after checking for the absence of any visible growth
• A sterile swab is dipped into the standardized suspension (prepared test sample ) of bacteria and excess fluid is removed by pressing and the swab on the sides of the test tube above the fluid level
• The swab is streaked over the entire surface of the agar with an aim of getting uniform inoculations. A final sweep with the swab can be made around the rim of the petridish.
• In the case of testing Streptococci 5-10% sheep blood agar is used for inoculation.
• The inoculated plates are allowed to stand for 3-5minutes but no longer than 15 minutes for any excess of moisture from the inoculum to be absorbed by the agar before applying antimicrobial discs.
• The discs are placed on to the agar surface using disc dispenser or sterile forceps, not closer than 24 mm (center to center), 14 mm (periphery).
• Each disc is gently pressed on the agar with the help of forceps to get complete contact with the agar.
• The plates are to be kept in the incubator within 15 minutes of applying the disc and incubate for 18 hours. Plates must not be incubated under increased concentration of CO2, as this will alter the zone of inhibition.