SOP for Microbial Monitoring of Drain Points in Pharma Sites

In short: Drains are a known reservoir for microorganisms in pharmaceutical plants. This is an example SOP for swabbing drain points and counting bacteria and fungi. It is an illustrative template: adapt it, and set your own frequency and limits, under your own quality system.

What the regulations say about drains

EU GMP Annex 1 (Manufacture of Sterile Medicinal Products, 2022), section 4.9, says sinks and drains should be prohibited in grade A and grade B areas. In other cleanrooms, air breaks should be fitted between the machine or sink and the drains. Floor drains in lower-grade cleanrooms should have traps or water seals that prevent backflow, and should be regularly cleaned, disinfected and maintained.

Annex 1 gives no drain-specific sampling method, frequency or numerical limit. Those are decisions for your contamination control strategy and your own risk assessment, so they appear below as example in-house criteria.

See also: SOP on microbial testing of drain water, Production of sterile pharmaceutical products and SOP for microbial culture management.

1. Objective

To describe how microbial contamination at drain points is monitored in manufacturing and related areas of [site name].

2. Scope

This SOP applies to the drain points listed in the site drain monitoring plan, which should be drawn up from a risk assessment (for example grade of the room, product exposure, and proximity to open product or equipment). Drains are not allowed in grade A and B areas (Annex 1, 4.9), so this SOP concerns drains in other areas.

3. Responsibilities

4. Procedure

4.1 Sampling

1. Prepare sterile swab sticks. After sterilisation, mark each with the location ID and the sampling date.
2. At the drain point, swab the critical part of the drain (for example the drain opening, trap and surrounding rim) and collect the sample.
3. Place the swab in its tube of diluent and vortex so the organisms transfer to the suspension.
4. Use the suspension for the tests below.

4.2 Total aerobic bacterial count

• Medium: soybean casein digest agar (SCDA).
• Method: pour plate.

1. Inoculate 1 ml of the suspension in duplicate into pre-sterilised Petri plates.
2. Pour molten, pre-sterilised SCDA into each plate and mix.
3. Incubate the plates.
4. Count colonies on each plate, take the average of the two, correct for the dilution factor (1:10 in this example), and report in cfu per swab.

4.3 Total fungal count

• Medium: Sabouraud dextrose agar (SDA).
• Method: pour plate.

1. Inoculate 1 ml of the suspension in duplicate into pre-sterilised Petri plates.
2. Pour molten, pre-sterilised SDA into each plate and mix.
3. Incubate the plates.
4. Count colonies, average the two plates and report in cfu per swab.

4.4 Controls

For every medium used, run a positive control (inoculated medium) to confirm fertility and a negative control (uninoculated medium) to confirm sterility. Record the results with the batch of medium used.

4.5 Pathogen testing

Test for the following, using the site’s validated pharmacopoeial method:

• Escherichia coli
• Salmonella
• Pseudomonas aeruginosa
• Staphylococcus aureus

4.6 Frequency (example in-house criterion)

Frequency is set by the site, based on the risk assessment and the area. State it in the monitoring plan, for example “weekly for drains in rooms with open product, monthly elsewhere”. These figures are only an illustration.

4.7 Acceptance criteria (example in-house criteria)

The limits are not set by Annex 1 or the pharmacopoeias for drain swabs. Set alert and action levels from your own trend data, and describe the actions on exceeding them (investigation, drain cleaning and disinfection, re-sampling, impact assessment on product).

4.8 Records

Record the sampling date, location ID, medium lot, results, controls and analyst in the annexure. Keep these records at least 1 year after the expiry date of the respective product batch (EU GMP Part I Chapter 4 section 4.11, or 5 years after QP certification if longer; 21 CFR 211.180(a)), longer if local law or the marketing authorisation requires.

5. Abbreviations

Frequently asked questions

Are drains allowed in sterile manufacturing areas?

Not in grade A and grade B areas. Annex 1 section 4.9 prohibits sinks and drains there. In other cleanrooms, they need air breaks and traps or water seals, with regular cleaning and disinfection.

What limit applies to a drain swab?

No regulator gives one. Each site sets its own from risk assessment and trending data.

Why test drains at all?

Drain water and biofilm can support bacteria such as Gram-negative organisms, and backflow or splashing can spread them to equipment and rooms.

References

1. European Commission, EudraLex Volume 4, Annex 1: Manufacture of Sterile Medicinal Products (Commission guidelines C(2022) 5938, 22 August 2022), section 4.9.
2. European Commission, EudraLex Volume 4, Part I, Chapter 4: Documentation (2011), section 4.11.
3. US FDA, 21 CFR 211.180(a), General requirements.