Homemade agar culture plates + swab test

Where to buy & price

Just examples of where to look and roughly what to expect to pay, get everything from wherever works for you, at whatever price you find.

Unflavored gelatin ~KSh 100–150. Bouillon cube (Royco) ~KSh 10–20. Clear containers, reused or bought cheaply.

Cold storage / timing

Refrigerate ~30 minutes to set faster (or 1–2 hours at room temperature); store cool and use within 2–3 days.

Reagents & materials required

Procedure, step by step

1. 1

   Dissolve 1 bouillon cube in 2 cups of hot water to make a nutrient broth, then stir in about 4–5 tablespoons of unflavored gelatin until it's fully dissolved.

2. 2

   Pour the warm mixture into several small, clean, clear containers (small plastic cups or reused jars work) to a depth of about 1cm each.

3. 3

   Let the mixture cool and set, refrigerate for about 30 minutes, or leave at room temperature for 1–2 hours, until it's firm like jelly. These are your homemade agar plates.

4. 4

   Once set, use a clean cotton swab to swab a specific surface (a doorknob, a phone screen, your hand before and after washing), then gently rub the swab across one plate's surface in a zig-zag pattern. Use a fresh swab and a fresh plate for each surface you test, and label each one.

5. 5

   Cover each plate loosely (a paper towel works, or prop the lid slightly open) and store them somewhere warm and undisturbed for 2–3 days.

6. 6

   Check daily without opening the containers, photograph any spots, fuzzy patches, or cloudy growth that appear, these are bacterial or fungal colonies.

7. 7

   Once you're done comparing, dispose of the plates by sealing them inside a bag before throwing them away.