Explain Procedure for Preparation of Bacterial Smear?
Now carry out the exercise using the steps enumerated herewith:
1. Collect swab samples from the suitable sampling sites e.g. refrigerator shelves, fruit bin or door gasket, cutting board, kitchen counter top, utensils etc.
2. For swabbing, moisten a swab head in the broth and press out the excess solution against the interior wall of the test tube.
3. Rub the swab head over a portion of the sampling site gently and rinse it in broth. Press out excess solution.
4. Rub the same swab on another portion of same sampling site and rinse in the broth. Repeat the process for remaining portions of the sampling site.
5. Break off the swab and put only swab head in the screw capped tube.
6. Store samples in the refrigerator prior to use.
7. Mix the sample by rolling in between hands and make dilutions from 10-1 through 10-5.
8. For total aerobic plate count, plate 0.1 ml each of the undiluted sample and dilution tubes on to PCA plates and incubate at 37°C for 24 hours.
9. For yeasts and moulds, spread 0.1 ml of undiluted sample and dilution tubes (10-1 and 10-2) on PCA - antibiotics plates. Incubate the plates at 28 + 2°C for 5 days.
10. Count the colonies and calculate CFU/100 cm2 surface area or CFU per site for total aerobic plate count and yeast and mould counts.