1.0 OBJECTIVE
To lay down a procedure explanation of why Petri dishes are inverted.
2.0 SCOPE
This SOP is applicable for
3.0 BACKGROUND
NIL
4.0 RESPONSIBILITY
4.1 QC-microbiologist
4.2 QC-Executive
4.3 QC-Head
5.0 PROCEDURE
5.1 A
Petri dish (plate) with “solid” culture media is kept in an inverted position
(upside down) during incubation so that condensation droplets will
not fall on the agar's surface (as such droplets are potential sources of
contamination).
5.2 Asides
that, the evaporation of water from the media if incubated in the normal
position could cause the media to start drying thereby affecting the ideal
microbial growth conditions and increasing microbial count errors.
5.3 Placing
plates upside down also makes them easier to handle and identify since the
labels are placed underneath the dishes and not on the lids.
5.4 It should however be noted that pouring media at higher
temperature causes excessive moisture accumulation on the lids of the Petri
dishes. So, it's advisable that you start pouring when the temperature is about
45°C (cool-down period).
0 Comments