Microbial Data Deviations (MDD)

Dear members, Does anyone know how to handle Microbial Data Deviations (MDD)?

Same as any other deviation, but remember the limits are less stringent. You can also not use statistics (normal gaussian distribution).

Dear Boomer,
Thanks for your reply and contributing in this discussion . I’m still a little hazy about it. Do you follow an OOS investigation instruction for MDD case or just should be treated as a deviation?
Kind regards,

There is no difference in results for an OOS/LIR/CFI/deviation/investigation. However, always follow your SOP! For micro. the specifications are different only. As an example you will ask;

  1. Was the media ‘growth promoted’?

  2. Was there a ‘positive’ control (was it ATCC)?

  3. Was the right temperature and time of incubation used?

  4. Other…

I should explain more clearly. The purpose of an OOS/LIR/CFI/Deviation/Investigation is to find the TRUTH! But the questions and who is asking them is different. For an;

  1. OOS it is the QC Manager
  2. LIR it is the Validation Chemist (or Microbiologist in your case) or Validation Manager
    3 CFI it is the Project Manager

The answer may be different depending on circumstances. For example;

  1. The OOS may ascertain the lot has a high micro count
  2. LIR demonstrates a ‘validated’ micro method
    3 CFI indicates the lot was manufactured as indicated
  3. But the finished lot is contaminated by anaerobic spores coming from the raw material which passed an aerobic micro test.

Dear Boomer,
Thanks for taking the time to explain your point of view on MDD. The main question is if you consider MDD in the general SOP of Deviations or you may handle it in specific SOP. I suppose you should see it in a separate one as you often lose samples in MDD case. What do you think?
KInd regards,

I agree with you, but it is ‘very’ rare that a company would have a separate deviation SOP for micro. (write the SOP). It makes little sense to ask an analytical chemist (who has no micro. training) to investigate a micro. deviation. Thus, you must follow the spirit of a general SOP but also be aware of the fact that micro. is different.

In my case I was trained as a chemist (>40 years ago) but have 3 years of micro. training.

SOP for Handling of Out of Limit Results in Environmental Monitoring and Water Analysis _ Pharmaceutical Guidelines.pdf (497.4 KB)SOP for Handling of Out of Specification Results in Microbiological Testing _ Pharmaceutical Guidelines.pdf (277.9 KB)


A procedure shall be in place for handling of the microbiol out specification in products, Environmental monitoring and Water, Gases…etc. Here i have enclosed for your reference and develop a new SOP by using these SOPs reference. You may revert me if you still need any information

Thanks & Regards

Pulla Reddy Karnati.