USP <797> Personnel Competency Q&A

On September 18, Dr. Michael Berg, Technical Director Pace® Building Sciences, and Rhonda Lintner, Pace® Account Executive, presented a webinar on the USP <797> Personnel Competency requirements.  

Watch On-Demand: USP <797> Personnel Competency and Environmental Monitoring 

After the formal presentation, Michael and Rhonda answered numerous practical questions from attendees. In addition, we received several more questions after the session. In this post, we share some of the most compelling and critical questions and answers from our experts. 

Q: What are negative and positive controls, and are they necessary? 

A: Media devices used for USP <797> sampling should come with a certificate of analysis (COA) certifying that the growth medium is appropriate, supports the growth of microorganisms, and is sterile. However, a lot of things can happen during shipping. For example, the media may be temporarily stored under conditions that are too hot or too cold. Damage to the packaging can also introduce microorganisms to the media, allow in excess moisture, or allow the media to dry out such that it no longer supports growth.  

This damage isn’t always readily apparent, so negative and positive controls are used to confirm that a media lot was not only good when the manufacturer shipped it, but that shipping and handling did not damage the media, rendering it unusable for USP <797> compliance.  

Negative controls are filled with the sterile nutrient medium but are not manipulated during the test. The purpose of the negative control is to indicate that the medium itself is free of contamination and to ensure that any growth observed in the test samples is a result of contamination during the compounding process, and not due to contaminated media. To validate this, the plate should show no microorganism growth after the incubation period. 

Positive controls are intentionally inoculated with a small number of appropriate nonpathogenic microorganisms to demonstrate that the growth medium can support microbial growth. This ensures the sensitivity of the test and confirms that if contamination is present, the medium will support growth so it can be detected. 

The 2022 revisions to USP <797> require documentation of the COA, but do not expressly mention positive and negative controls. However, it’s important to remember that the chapter defines the minimums for a compounded sterile preparation (CSP) quality program. Including positive and negative controls is a good example of a standard operating procedure (SOP) that should be considered in your risk assessment and is integral to an effective quality program. For our part, while we have confidence in the media we supply, we have no way of knowing how the media is handled during shipment. For that reason, we always recommend including positive and negative controls.  

Q: In the webinar, you said that USP <797> is an enforceable standard. Can you expand on that? How is an industry “standard” enforceable? 

A: The United States Pharmacopeia (USP) is a nonprofit organization that sets standards for medicines, food ingredients, and other substances. While the USP does not have the power to enforce these standards, Authorities Having Jurisdiction (AHJ) do. This includes regulatory bodies such as: 

• The Joint Commission (TJC) – Applies to hospitals and healthcare only. 

• Det Norske Veritas (DNV) – Responsible for the NIAHO® (National Integrated Accreditation for Healthcare Organizations) 

• State Boards of Pharmacy – States may mandate adherence to USP <797> exactly as written or adopt a higher standard for attaining and maintaining licensure. 

• Pharmacy Compounding Accreditation Board (PCAB) – The PCAB is a voluntary accreditation board, operating under the umbrella of the Accreditation Commission for Health Care (ACHC). PCAB standards typically surpass those set by the USP. 

• Food and Drug Administration (FDA) – While compounded drugs do not undergo FDA approval, the agency is involved in setting and enforcing regulations and guidelines to ensure that compounding is performed under safe and appropriate conditions. 

Q: You mentioned the single and dual-plate protocols. Do you typically recommend one over the other? 

As Michael explained in the webinar, for the dual-plate protocol you need to collect two samples per area. One plate should have a Tryptic Soy Agar (TSA) medium, and the other typically uses fungal growth medium such as Sabouraud Dextrose Agar (SDA) or Malt Extract Agar (MEA).  USP <797> also allows for a second TSA plate to be used. The first TSA plate is incubated at 30 - 35°C for at least 48 hours. At the same time, the SDA, MEA, or second TSA plate is incubated at 20 – 25°C for at least 5 days. After incubation, all colonies are counted on each plate, but each medium is evaluated separately against threshold levels. Both plates must be below the action threshold for the area to pass.  

In the single-plate protocol, only a TSA plate is used. The plate is incubated first at 30 – 35°C for at least 48 hours and subsequently for 5 days at 20 – 25°C. Colonies are counted after the first incubation and again after the second incubation.  

Because turnaround time (TAT) is shorter for the dual-plate protocol, many of our clients typically follow that path. It also provides better recovery of fungi, providing an extra degree of certainty to your results. On the other hand, the single-plate protocol is acceptable under the USP <797> standards. As always, check with your SOPs and any AHJ. 

Whether ordering plates for the dual-plate or single-plate protocol, remember that some analysis may require irradiated plates. See the chart below for guidance. We sell both irradiated plates and standard plates online at the Pace® shop. 

Again, our webinar is now available on-demand - USP <797> Personnel Competency and Environmental Monitoring. If you have additional questions, our USP <797> experts are here to help.  

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