Abstract

Sterility tests described in official compendia are carried out by membrane filtration or by direct inoculation into suitable culture media. About 14 days are needed to provide results and release products for sale, so speed is of the essence in rapid microbiological methods. Solid phase cytometry is a fast innovative method for testing the sterility of injectable medications. It is based on the detection of viable cells by using reagent viability markers which permeate the cell membrane, and are cleaved by non-specific sterases to form fluorochrome, which is detected by a Chem Scan RDI®. This study set out to evaluate this technology when applied to the sterility test in a 0.9% sodium chloride injection solution, using Chem Scan RDI® equipment. Microorganisms recommended by the official compendia Clostridium sporogenes NCTC12935 (ATCC 11437), Pseudomonas aeruginosa NCTC12924 (ATCC 9027), Staphylococcus aureus NCTC10788 (ATCC 6538), Bacillus subtilis NCTC10400(ATCC 6633), Aspergillus brasiliensis NCPF2275 (ATCC16404) and Candida albicans NCPF3179(ATCC 10231), and two “in house” microorganisms, Micrococcus luteus and Staphylococcus epidermidis, obtained from monitoring the pre-sterilization bioburden, were evaluated in order to validate the proposed method. When the solid phase cytometry method was compared to the traditional membrane filtration sterility test for all the microorganisms tested, it was found to be significantly faster in that it reduced analysis time from 14 days to approximately 3 h.

Key words: Solid phase cytometry, sterility test by membrane filtration, validation.

Abbreviation

CFU, Colony-forming unit; SPC, solid phase cytometry; MF, membrane filtration; VBNC, viable but not culturable.