A STUDY OF THE USE OF RAPID METHODS FOR PRESERVATIVE EFFICACY TESTINGOF PHARMACEUTICALS AND COSMETICS

Three rapid microbiological methods, impedance, the direct epifluoresc ence technique (DEFT-MEM) and ATP bioluminescence (ATP-B) were evaluat ed for their applicability to preservative efficacy testing (PET) of p harmaceuticals and cosmetics. A good correlation between rapid method response and total colony counts was obtained for untreated suspension s of Staphylococcus aureus, Pseudomonas aeruginosa and Candida albican s with all three methods but, for Aspergillus niger, with impedance on ly. For chlorhexidine-treated suspensions of Staph. aureus and C. albi cans, a good dose-response curve was obtained with impedance, but ATP- B and DEFT-MEM methods underestimated the kill by the order of 1-6 log s. From the results of this study it is concluded that impedance offer s an alternative method to colony counting methods for PET but, at the ir present level of method development, neither DEFT-MEM nor ATP-B can be considered as satisfactory.