Lab animal swab testing (LAST)

 

Purpose

This test is used to check the antibiotic residues.

Uses of antibiotics


  1. Therapeutic use
  2. Prophylaxis
  3. Growth promoters

Withdrawal period


It is the time required for residual of toxicological concern to reach safe conc. Residues should not come in milk, meat, and egg so that resistance can be prevented.

Antibiotic residue


Parent drug or its metabolites in egg, milk, and meat.

Safe concentration


Minimum residual level. It is measured in ug/kg.

1.Therapeutic use of antibiotics


It is used to treat disease, pyrexia, inflammation, or wound.

2.Use of antibiotics as a growth promoter


It causes thinning of the intestinal wall. This results in increased absorption of nutrients. More absorption results in more growth of the body.  It is used in poultry only.

3.Prophylaxis


For the prevention of disease (e.g., in poultry)

Drawback


Side effects and resistance.

Swab


Any absorbent material used for cleaning wounds, applying medication and packaging specimens.

Types of swab


  1. Cotton bud
  2. Guided swab

Transport media


  1. Viral transport media
  2. Gel-based media
  3. Liquid amines media
  4. Sterile saline media

Equipment


  • Urine bag/plastic jar
  • The bacterial suspension (Bacillus subtilis)
  • N5 disc (5Types of microbes that are sensitive to Neomycin)
  • Incubator
  • Agar plate

Procedure


  1. Collect urine
  2. Plug incubator (29-31oC required temperature)
  3. Preparation of plate.
  4. Take petri dish having agar
  5. Start streaking of Bacillus subtilis gently from X and so on.
  6. Tilt X 4 times at ¼ (90o angle) angle and streak 4 times.
  7. Then tilt X 2 times at ½ (180o angle) and streak.
  8. Dip two swabs in urine bag, then break handles and place them on Petri dish.
  9. Do not touch swabs with hands.
  10. Place the disc with the help of forceps.
  11. Incubate for 18-24 hours at 29-31o C.

There could be 3 possibilities


Due to the growth of bacteria, creamy, grayish, opaque color will appear in the petri dish.

  • If there is a clear zone around the swab, it shows that urine has some antibiotic residues that have killed bacteria and color has not appeared.
          The size of the clear zone around the disc is 16-24 mm.


Result: Do not market animal because it has drug residues.

  • If there is no clear zone around the swab.
         The size of the clear zone around the N5 disc is 16-24 mm, Test is negative.

Result: We can market animals.

  • If the clear zone around N5 disc is less than 16 mm, we will re-run the test.

Result: Do not market animal, repeat the test.

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