Recovery studies of microbiological sampling methods to support cleaning validation in the Pharmaceutical industry

This present work describes recovery studies for direct and indirect sampling methods in combination with microbiological enumeration test methods for bioburden determination on the shared manufacturing equipment surfaces in support of cleaning validation. The swab and rinse sampling methods were developed in order to obtain a suitable recovery (>35 %) for five challenge Gram-negative rod, Gram-positive cocci, yeast, mold and spore former microorganisms and three types of equipment material (plastic, glass, and stainless steel) in this study. The swabbing involved moistening the swab with sterile saline and swabbing the area (100 cm2) to be sampled in an overlapping zigzag pattern. Rinse sampling was performed using a separate sampling rinse with a fixed volume of water for injection from a piece of equipment. The swab and rinse samples were tested using the plate count and membrane filtration methods, respectively. The recovery rate is higher for the swab sampling method (60.5 %) compared to the rinsing method (46.8 %). The combination of the developed sampling and the microbiological enumeration test methods gives a good recovery (>36.17%) with high precision (RSD<19.25%). The proposed methodology can be used to perform cleaning validation successfully.