Microbiological monitoring during aseptic handling:Methods, limits and interpretation of results

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 monitoring (MM) and media fills are used for environmental and process control. In this study, the application of MM methods during aseptic handling inside, or related to working in, a laminar airflow cabinet or safety cabinet in hospital pharmacies is described and evaluated. Results are expressed as colony forming units (cfu) and Contamination Recovery Rate (CRR; the rate at which MM samples contain any level of contamination -USP<1116>-). For trend analysis, a rolling CRR is developed (a rolling CRR calculates a CRR using a predetermined number of most recent samples). Of all MM methods, glove print is the most informative. The added value of air sampling is doubtful. Because of microbiological as well as statistical considerations, the use of CRR for assessing MM results is advised. Glove prints, in general, give the highest CRR. A CRR < 10% is a realistic limit for MM during aseptic handling in hospital pharmacies. A rolling CRR, calculated using the last 100 samples, is a good compromise between reliability of the CRR value and timely prediction of process changes.