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Specimens in a petri dish

Determining How You Will Handle Viable Sampling and Incubation

With the release of the new version of USP <797>, you will have a lot of changes to make to your sterile compounding operation. One of the most challenging may be updating your viable sampling program and deciding how to handle increased sampling frequencies. There are a variety of factors that need to be considered when determining whether you will collect your own viable air and surface samples, and whether you will incubate these samples. Each organization is different and needs to evaluate their situation.

How frequently will you be sampling?

This will be based on CSP Categories compounded and if you want to do more than chapter requirements. Many organizations that will be compounding Category 1 and 2 CSPs are looking to collect air samples monthly so that they can trend air and surface data together, giving them a clearer picture of their microbial state of control. This increased frequency is justification for collecting your own samples.

Do you have the capacity to sample?

You must evaluate the current workload and determine if this work can be taken on. You may need to hire to be able to accomplish internal sampling. You also have the option to outsource sampling. Even though certification providers might not be able to meet this need, there are companies that offer viable sampling services. Many of them are microbiology labs. If you are fortunate to operate close to one of these service providers, you may be able to outsource sampling to them.

If you decide to take sampling in-house, will you have staff trained in every location or will you create a team that travels from location to location to sample?

There are benefits to both options. But the most important consideration is that those who collect viable air and surface samples must be trained and deemed competent in collection techniques and processes. So, it may come down to how many staff members for which you want to train and maintain competencies.

Will you incubate the samples in the pharmacy, send them to the clinical lab, or outsource to a contract lab?

There is a lot to consider when incubating in-house. You are now essentially becoming a microbiology lab. If you decide to incubate your own samples, you’ll want to read USP <1117> Microbiological Best Laboratory Practices. In addition to the information in this informational chapter you will need to evaluate your ability to meet the following:

  • You must have space for at least two incubators. You may need more depending on how full your incubators will be at any given time.
  • You must monitor these incubators daily.
  • You must clean and perform preventative maintenance on the incubators.
  • You should perform installation, operation, and performance qualifications on the incubators.
  • You must have a dedicated space to read the samples.
  • Staff must be trained and deemed competent to read the samples.
  • You must form a relationship with a contract lab for identifications.
  • You must understand how to report the results.

If you have clinical microbiology labs within your organization, they may or may not take your samples. They are only accredited to test human specimens, so many won’t even touch them. If your clinical lab is willing and able to take on the work, discuss reporting with them. In many cases, the report format will be that of patient specimens, meaning you are likely to get one report per sample! Resulting in a lot of paperwork to sift through.

Outsourcing to a contract lab takes the responsibility off the sterile compounding pharmacy to be trained and competent in reading viable air and surface samples. It is expected that this will be a focus of regulators and surveyors, so if you want to avoid this scrutiny, outsourcing will be your best option. Otherwise, you must be sure you have received the appropriate training.


There is a lot more to collecting, incubating, and analyzing viable samples than what you see in USP <797>. If you are unsure of the best option for your organization, reach out! Pure Microbiology is here to help.

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