The IRB BART tester had growth after a couple days, but after a few more days the growth (positive reaction) went away and the vial was clear again. What would cause this response?

Document ID

Document ID TE2621

Published Date

Published Date 27/05/2017
Question
The IRB BART tester had growth after a couple days, but after a few more days the growth (positive reaction) went away and the vial was clear again. What would cause this response?
Summary
IRB BART shows positive growth but then turns back to clear
Answer
Day 7 onwards IRB tester now again is positive for “growth”
This response occurs, but not commonly, and it is therefore not included in basic reaction interpretations.
(Not common is less than 1 in a hundred incidents, some that are 1 in a thousand and these are discounted from basic interpretation schemes and duplicate testing is a good way to limit the effects of these “outliers”).
Interpretation:
A positive reaction is limited to the word “growth” and in this case would think that reaction was cloudiness (due to suspended dispersed IRB biomass and seen day 2 to 4).
The ensuing negative reaction is not defined but presume it relates to a re-occurrence of clarity in the IRB liquid column rather than cloudy), the highest probability was the “growth” had settled to the bottom of the IRB- Bart tester causing the liquid column to now be clear (possibly the column has a yellow hue at this time).
Day 7 was a time when there was a secondary growth of IRB in the column commonly originating from the biomass settled into the floor of the tester. That elevation would have probably been because the settled biomass now reacted to reductive conditions generated a little gas (such as carbon dioxide) which caused the biomass to float back up into the column (like micro-submarines!).
This type of growth reaction is not unique to the IRB but also occurs in the HAB tester but at incident levels too low to warrant routine recognition as a common reaction pattern.