Microbiological controls of aseptic handling in Dutch hospital pharmacies: Results, limits, and methods for assessing

'Aseptic handling is the procedure to enable sterile products to be made ready to administer using closed systems' (EU Resolution CM/Res(2016)2). Microbiological controls are an important part of the overall assurance of process and product quality of aseptic handling. They consist of the End-of-Session Broth Test (ESBT) using Tryptone Soya Broth, Microbiological Monitoring (MM) using Ø 55- and 90-mm agar plates and a periodical Operator Broth Transfer Validation Test (OBTVT) using Tryptone Soya Broth. This study describes the results of these controls over a 7-year period, involving between 44 and 49 pharmacies (mostly hospital pharmacies). All pharmacies use a web-based programme for processing, evaluation and assessing microbiological controls ('Microbio'). Aggregated results in Microbio are used for benchmarking and feedback information.

The objective of this study is to analyse the results of the 7-year period and to develop methods for assessing of, and determining realistic limits for, microbiological controls during aseptic handling. As secondary objective the role of Microbio is highlighted.

Results of ESBT are expressed as Contamination Rate (CR), which is the percentage of units filled in a process simulation that are positive for microbial growth after incubation. Compared with the first 3 years of the study, the results in the last 4 years were significantly better: mean CRs are 0.20 and 0.11, respectively (p-value <0.01). For assessing CRs of ESBT, the approach 'the more frequent samples with growth, the stronger the corrective actions' was adopted. Levels of investigative and corrective actions, based on the 95% Upper Confidence Limit, are suggested. Microbiological Monitoring (MM) during aseptic handling into a laminar airflow cabinet or safety cabinet consists of settle plates, glove prints, contact plates of the worktop and surface bioburden determination of disinfected ampoules and vials. The results are expressed as the Contamination Recovery Rate (CRR), which is the rate at which MM samples contain any level of contamination. During the study period, the results of glove prints and contact plates improved substantially. The most probable explanation of this finding is improved disinfection procedures of the gloved hands, the worktop inside LAF/SC and the ampoules and vials. Results of settle plates did not change. There were too few results available to evaluate the surface bioburden of disinfected ampoules and vials. Benchmarking and feedback information from Microbio may have contributed to the improved ESBT and MM results. Results of the Operator Broth Transfer Validation Test (OBTVT) are expressed as Contamination Rate (CR). The target is zero samples with growth (CR = 0). The overall CR result over the study period is 0.50%. This is worse than ESBT (overall CR is 0.14%). This is probably due to the high number of critical steps in OBTVT compared to ESBT.

Results of microbiological controls improved during the study period. Realistic limits as well as methods for assessing ESBT and MM results are given and discussed.