Evaluation of the ScanRDI® as a Rapid Alternative to the Pharmacopoeial Sterility Test Method: Comparison of the Limits of Detection

Two sterility test methods, the ScanRDI® rapid sterility test and the United States Pharmacopeia/European Pharmacopoeia/Japanese Pharmacopoeia (USP/EP/JP) compendial sterility test, were compared with respect to the limits of detection for the presence of viable microorganisms in aqueous solutions at low inoculation levels. The ScanRDI® system employs a combination of direct fluorescent labeling techniques and solid-phase laser scanning cytometry to rapidly enumerate viable microorganisms from aqueous samples, whereas the compendial sterility test is a qualitative, growth-based method that uses a visual assessment of turbidity to indicate microbial contamination. Eight microorganisms were evaluated, seven compendial microorganisms (Clostridium sporogenes, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Aspergillus niger, Candida albicans) and the Gram-positive anaerobe Propionibacterium acnes. The number of viable organisms was estimated using the ScanRDI® method and the conventional sterility test method using most probable number methodology. The mean difference between the methods was computed and 95% confidence intervals around the mean difference were estimated. The ScanRDI® method was found to be numerically superior and statistically non-inferior to the compendial (USP/EP/JP) sterility test with respect to the limits of detection for all organisms tested.