My last recipe of gelatin failed. I suspect there wasn’t enough gelatin in the mixture to keep the medium solid at 95 degrees Fahrenheit. I am going to try a new recipe by increasing the gelatin ratio to water. I still suspect that this might not be enough as the high temperature of the incubator.

New gelatin recipe:

  • 1/2 C Water [Previously 1 1/2 C]
  • 1.5 gelatin packet [Previously 2.5 packets]
  • 1 cube of beef stock powder [Previously 6 cubes]
  • 1 1/2 t sugar [Previously 6t]

 

Lets see how this goes.
  1. #1 Exposed to air for 30 minutes
  2. #2 Exposed to air for 30 minutes and UVC lamp for 1 hour
  3. #3 Not exposed to air
  4. #4 Swabbed from computer keyboard
  5. #5 Swabbed from computer keyboard-UVC lamp for 1 hour
  6. #12 Swabbed from computer keyboard-UVC lamp for 3 hours
  7. #6 Exposed to air for 30 minutes. (I repeated these tests. I should have been with agar)
  8. #7 Exposed to air for 30 minutes and UVC lamp for 1 hour. (I repeated these tests. I should have been with agar)
While I started this experiment, I received my package of agar powder from Amazon. I made a quick Agar juice block treat of 2 Cups of juice and 2 Tablespoons of agar powder. Wow-this stuff sets much better than gelatin. It solidified at room temperature instantly. Excitedly (who gets excited by this stuff), I whipped up an agar batch using the following recipe
  • 1/2 C Water
  • 1 1/2 teaspoons agar powder
  • 1 cube of beef stock powder
  • 1 1/2 t sugar
I accidentally let the agar cool too much. As a result, it was a bit difficult getting into the petri dishes. Not all the petri dishes have an even coating of agar and a few are pretty lumpy. Undeterred, I still wanted to proceed with the experiment.
Agar samples:
Agar samples
  1. #8 Not exposed to air
  2. #9 Swabbed from computer keyboard
  3. #10 Swabbed from computer keyboard-UVC lamp for 1 hour
  4. #11 Swabbed from computer keyboard-UVC lamp for 3 hours
  5. #13 Swabbed plate after dishwasher cleaning
  6. #14 Swabbed downstairs toilet
  7. #15 Swabbed downstairs toilet after cleaning with DIY disinfectant
  8. #16 Refrigerator handle
  9. #17 Swabbed spoon after dishwasher cleaning
To keep things super sterile, I washed the petri dishes from the last experiment in warm soapy water, and then placed them under the UV sterilizer for at least 2 hours with the lids on. I did the same with the Q-Tips. I am not sure how I would sterilize the Q-tips other than dunking them in alcohol.
Wait 1.5 days . . .


Exposed to 30 minutes of air.

 

Exposed to 30 minutes of air + 1 hour UVC light. Slightly less cloudier than #1.

 

Not exposed to air. Hmmm-this should have been cleaner that #1. Poor cleaning practices?

 

Swabbed from computer keyboard. Pretty cloudy.

 

Swabbed from computer keyboard + 1 hour UVC light.

 

Exposed to air for 30 minutes. Overall less cloudier than #1, but stuff could have shifted to the side.

 

Exposed to air for 30 minutes + 1 hour UVC.  Odd that this is cloudier than #6. 

 

First agar medium. 

 

Swabbed from computer keyboard. Poor agar pour.

 

Swabbed from computer keyboard. Exposed to UVC light for 1 hour.

 

Swabbed from computer keyboard. Exposed to UVC light for 3 hours. The dense stuff in the bottom half is agar poured poorly.

 

Swabbed from computer keyboard. Exposed to UVC light for 3 hours. Again the dense looks is from uneven agar.

 

Swabbed plate that was just cleaned from dishwasher.

 

Swabbed from downstairs toilet.

 

Swabbed from downstairs toilet after it was cleaned. Hard to tell, but this is cleaner than #14.

 

Swabbed from refrigerator handle. 

 

Swabbed from utensil from dishwasher. This was a very lump medium and not accurate.

 

Side by side for 30 minute air exposure. #2 additional had 1 hour of UVC light. It appears the UVC light had minimal effect.

 

Side by side of 30 minute exposure (1 & 2) with no exposure (3). This suggests I need to create the samples in a cleaner environment.

 

Side by side of 30 minutes of exposure. #7 had 1 hour of UVC light. 

Conclusion

Gelatin sucks for these tests. Even though I upped the gelatin ratio, it melted at the incubation temperatures. Agar, on the other hand if prepared well, is ideal. I am going to need to be cleaner in my agar preparation and run through another set of tests. Upward and onward!

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