Challenge testing: principles and practice

Abstract

It is difficult to predict accurately the ultimate effectiveness of a preservative in any but the simplest cosmetic or pharmaceutical formulation. It is thus necessary to obtain some assurance of its likely in-use performance in a formulated product. A challenge test is a procedure in which a product is challenged by exposure to specified types of bacteria and fungi to determine whether it is adequately preserved. Assessment of preservative efficacy is needed over the intended shelf-life of that product. Test organisms should be representative of those likely to occur as contaminants during use and should consist of Gram-positive and Gram-negative bacteria, mould and yeast. In-house factory isolates obtained as a result of contamination of earlier batches of a product may also be included. The organisms, as single or mixed inocula, are inoculated (usually as a single challenge, although some advocate multiple challenges) into samples of the product and aliquots removed at appropriate intervals for the determination of survivors. Interpretation of data is normally based on pharmacopoeial or other official protocols. Challenge testing should be undertaken at the beginning, during and at the end of the shelf-life of the product. An alternative, the D-value, approach is open to criticism and further studies are required that utilize rapid methods, e.g. impedance, for the detection of survivors before these can be considered to be a suitable replacement for the more traditional but very time-consuming, viable counting procedures.

Emergence of resistance to antibacterial agents: the role of quaternary ammonium compounds—a critical review

“…Laboratory assays currently available include MIC tests for QACs, biocidal tests (i.e. European NF EN, American ATCC test methods) or standardised challenge tests for pharmaceutical/cosmetic products [28][29][30]. Although antibiotic resistance is commonly evaluated in clinical practice, there is no consideration of biocide susceptibility.…”

“…In the challenge test, the pharmaceutical cosmetic product is inoculated with bacteria, stored for a specified period and then sampled for survivors[30]. In France, pharmaceutical preparations are measured in the final container according to the European Pharmacopoeia (Volume 1 6.0 paragraph 5.1.3), and the test measures whether the activity changes over the storage period.…”

Evaluation of Cosmetics for Their Potential Contaminants and Drug Resistant Microorganisms

“…So that he involves in all the stages of cosmetic production until the complete production. He also performs the final challenge test for cosmetics evaluation [18]. The infections which occur in some particular situations are of great importance for example; use of cosmetics around eye area, on skin when it is damaged, on children Contents List available at RAZI Publishing Acta Scientifica Malaysia (ASM) …”

Development and validation of a microbial counting method for mebendazole oral suspension

“…The antimicrobial system used in the manufacturing of mebendazole oral suspension is important to ensure the stability and safety of the product with respect to microbiological purity, in addition to protecting the user from any health compromise due to product contamination. This is no substitute however, for the good manufacturing practices inherent in the manufacturing process of pharmaceutical industries (Pinto, Kaneko, Ohara, 2003;Russell, 2003). The conducting of a validation test for antimicrobial agent neutralization and for microbial counting method validation thus become key factors that will prove the method's effectiveness in recovering product contaminants.…”