Plate incubation temperature and inversion incubation

• We can incubate the same plate first at 32.5±2.5⁰ for 2 days and then at 22.5 ±2.5⁰ for remain 3 days. This is given in USP general chapter 1116. That was revised in 2017 and states that if the lower temperature is selected first to incubate the plates then the grow Gram positive Cocci (mesophillic) may be affected.

• These are often associated with human generated contamination so their recovery is important. Incubate to grow the slow growing microorganism.

• Infortent factor of incubation condition for the recovery of bacterial and fungals.
• 20-25⁰C for 72 hrs for fungal purpose 30- 35⁰C for 48 hrs for bacterial purpose.

• Fungal slow growing and low temperature bacterial growth high temperature total 5 days incubation period.

• Plates incubate inversion position because

1. When the plates are incubate in up right (normal) position water evaporation from the  media occurs.
2. Prevent the water drip down on the plate these cause mix up colonies.
3. Easy to handling.
4. Prevent the Dehydration of media.
5. Evaporation of water from the media can cause to media dryness.
6. Prevents contamination of other bacteria in the samples.

• Petri dishes were invented in 1887 by German physician Julius Petri.
• He improved upon the design of his mentor, Dr. Robert Koch, by inventing a small plate that has a slightly larger plate that fits over it to create smaller samples for bacterial growth.