Pharmacy OneSource Blog

Eric S. Kastango and Kate Douglass answer your questions about Environmental Surface Sampling

Environmental Sampling allows for the early detection of contamination at its source and allows you to measure your pharmacy’s state of microbial control. Contamination sources can include personnel, work surfaces, supplies, equipment and failure of engineering controls. Environmental Sampling is comprised of facility and personnel related metrics. Eric and Kate provide answers to some of your most frequently asked questions about surface sampling.

Which surfaces should be sampled?
According to the current Chapter 797, surface sampling is to be performed at the conclusion of compounding (simulating the worst case scenario) and must be performed “periodically.” Locations to be sampled must be documented on a sampling plan or diagram. Surface sampling performed inside the ISO Class 5 spaces at the conclusion of compounding provides direct information about the aseptic technique of the individual who is compounding. Surface sampling in other locations provides information about cleaning and material handling contamination control. Our best practice recommendations for the frequency and timing of surface sampling are based on the following:

Surface Sampling inside PECs during compounding: When surface sampling is performed at this time, it is an almost direct measure of staff aseptic technique because it verifies if staff are disinfecting items immediately before placement into the PEC; frequent disinfection of their sterile gloved hands; frequent disinfection of the deck and organization of their compounding supplies.
Surface sampling during dynamic working conditions on ISO 7 and 8 surfaces: When surface sampling is performed during this time it measures both the material handling contamination control procedures as well as the effectiveness of cleaning and disinfecting procedures. It is best performed at the end of the compounding day or shift.
Surface sampling at the beginning of the day before work begins in the controlled environment: When surface sampling occurs at this time, it only measures the effectiveness of cleaning and disinfection procedures.
When should surface sampling be performed?
According to the current Chapter 797, surface sampling is to be performed at the conclusion of compounding (simulating the worst case scenario) and must be performed “periodically.” Locations to be sampled must be documented on a sampling plan or diagram. Surface sampling performed inside the ISO Class 5 spaces at the conclusion of compounding provides direct information about the aseptic technique of the individual who is compounding. Surface sampling in other locations provides information about cleaning and material handling contamination control. Our best practice recommendations for the frequency and timing of surface sampling are based on the following:

Compounding risk level (more frequently at high risk level operations)
Best practices: Weekly sampling for high-risk compounding, monthly for medium-risk level compounding and at least quarterly for low-risk compounding.
Environmental sampling results history (more frequently at compounding facilities with no environmental sampling history and who desire to build knowledge about their state of control).
Tenure of compounding staff (more frequently when many compounding staff are new, inexperienced or when staff have not established a sampled history associated with environmental sampling; gloved fingertip sampling or media-fill testing).
Other factors which may impact work practices (i.e., more frequently during periods of short staffing; more frequently if custodial staff are assuming cleaning activities).
So if your pharmacy has never performed surface sampling before, at least integrate surface sampling with Gloved Fingertip Sampling (GFS) during media fill testing. Perform surface sampling at suitable locations at the same time that viable air sampling is being performed. We strongly recommend that RANDOM surface sampling and gloved fingertip sampling be performed near the end of the compounding day and be associated with a particular staff member and PEC. By performing it randomly, staff get great feedback about how clean they are keeping their gloves and DCA while compounding and you eliminate the Hawthorne effect (people behave differently when they know they are being tested).

Who is responsible for performing surface sampling?
Properly trained pharmacy personnel or subcontracted personnel from qualified vendors may perform surface sampling. Regardless of who performs, the pharmacy is still responsible for ensuring the performance of surface sampling even if it is outsourced to a vendor. Having written policy and procedure on how sampling is performed, documented and excursion strategies is the responsibility of the pharmacy.

What type of media should be used to perform surface sampling?
Surface Sampling is performed using general growth media (e.g., tryptic soy agar) to which neutralizing agents such as lecithin and polysorbate 80 have been added. These chemicals neutralize the effects of cleaning agents to help prevent false negatives.

What size plate should be used to sample surfaces?
USP 797 states that the surface area to be sampled is 24-30 cm2, which is roughly equal to a 55 mm plate. Remember these plates, called “contact” plates are different from the plates used to perform gloved fingertip sampling (GFS). Plates for GFS have concave media and are generally larger (e.g. 100 mm) to make it easier to sample each finger. Contact plates have a media surface that extends above the lip of the plate so that the media will contact the solid surface being sampled. Non-solid surfaces like wire racking, can be sampled using the swab method of sampling.

How is the surface sampling media incubated?
General growth media should be incubated at 30-35˚C for 48 to 72 hours. Since this is a warm temperature, condensation will form so the general growth media plates must be turned upside down (inverted; with media on the top side). If the TSA is not inverted, condensation will drip from the lid onto the agar and spread any contamination around the plate, growing a “lawn” or 1 big colony forming unit (cfu).

Is Surface Sampling required in Segregated Compounding Areas (SCAs)?
The chapter states that surface sampling shall be performed at locations inside the ISO Class 5 so yes, it must be performed inside the PECs located in SCAs.

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