The purpose of Pharmaceutical Compounding–Sterile Preparations (USP <797>)microbial testing is to provide standards that protect the health and safety of patients and healthcare workers involved in the sterile compounding process by reducing potential microbial contamination that can occur from an unclean environment. This chapter outlines required procedures that should be followed by all pharmacies, health care institutions, and other facilities that produce compound sterile preparations (CSPs). Understanding cleaning, sterility testing, environmental monitoring, training, and validation of personnel and engineering controls is essential for compliance with USP <797> guidelines. 


Assured Bio Labs offers assistance with compliance to environmental testing requirements in the U.S. Pharmacopeia Pharmaceutical Compounding–Sterile Preparations (USP <797>). To comply with USP <797> guidelines a facility will need to collect air and surface samples from areas used for CSPs. Gloved fingertip and media-fill tests are also required to ensure pharmacy personnel are performing sterile compounding preparations aseptically. 

Air Sampling

Air sampling should be performed every 6 months in all ISO (International Organization for Standardization) Class environments. A sufficient volume of air (typically  1,000 liters) is sampled using an agar plate impactor for volumetric air sampling counts from air sampling plates. These will be reported as colony forming units (CFU) per cubic meter of air. 

Surface Sampling

Surface sampling  is performed on a periodic basis (monthly if using the 2019 revision of USP <797>) using contact plates in all ISO classified areas with results reported as CFU per plate. 

Gloved Fingertip Sampling

Gloved fingertip sampling is performed as an initial competency evaluation that personnel must pass no less than three times (with a limit of zero CFUs) before being allowed to compound CSPs. Re-evaluation occurs annually for low and medium-risk CSPs and semiannually for high-risk CSPs. Results are reported separately as number of CFU per employee hand, however the CFU action level for gloved hands will be based on the total number of CFU on both gloves, not per hand. 

The Analysis

Once samples are received at Assured Bio, we will check them for damage and logged into our system which will send you a sample receipt form. Plates are incubated at different temperatures and time frames depending on the type of sample you send in and the version of USP <797> you are currently following. For example, single plate method TSA plates are incubated at 30-35°C for 48-72 hours to check for bacterial growth and then followed up by an incubation period for 5-7 days at 26-30°C to check for fungal growth. For media fill analysis, fungal growth is checked first and then bacterial with both incubating for 7 days at 26-30°C and 30-35°C, respectively. If any growth occurs, any distinguishable bacterial or fungal colonies are isolated to be prepped for PCR and sequencing if required. Once sequencing is completed, the sequences are run through BLAST to give an accurate identification of the organism to the genus and, typically, species level. A final report is then issued with the ID of the contaminants, their quantity,  and a pass/fail status for the sample based on ISO class. Contact us today to receive your free quote!


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