In method 8368 for Fecal Coliforms, why should the tube be inverted after the first 3 hours of incubation?

Document ID

Document ID TE7294

Version

Version 3.0

Status

Status Published

Published Date

Published Date 07/24/2018
Question
In method 8368 for Fecal Coliforms, why should the tube be inverted after the first 3 hours of incubation?
Summary
Tube inversion
Answer
In method 8368 for Fecal Coliforms, the tube should be inverted after the first 3 hours of incubation to remove bubbles formed as a result of dissolved gases being released by heating the media. These bubbles would very likely not be due to bacteria that early in the incubation. If the sample is positive, it would certainly show up within the next 21 hour incubation period.

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