3PC-002 Microbiological stability test of 15% topical resorcinol for quality control

Background and importance Hidradenitis suppurativa (HS) is an inflammatory skin disease that causes painful boils and abscess formation, especially localised in intertriginous areas. Resorcinol is a phenol derivate, and in topical self-treatment decreases the size and pain of HS lesions. Topical 15% resorcinol is prepared as a pharmaceutical compound and there are no data in the current literature on the microbiological stability of formulations of topical resorcinol 15%. The European Pharmacopoeia (EP) established acceptance criteria (chapter 5.1.4) for microbiological quality control of the compound. Previous to the microbiological quality assay, the EP also established the necessity of a suitability test of the method. Aim and objectives The objective of the study was to develop a microbiological growth assay to perform a microbiological stability test for quality control of this resorcinol formulation. Material and methods The composition of the formulation of topical resorcinol 15% tested was: resorcinol 15 g, purified water 15 g, sodium metabisulfite 0.1 g and lanette base cream qs 100 g. To determine the ability of microorganisms to grow in the formulation, several reference strains, according to the EP (chapters 2.6.12 and 2.6.13) were selected: Pseudomonas aeruginosa (ATCCVR 9027TM), Candida albicans (ATCCVR 10231TM), Aspergillus brasiliensis (ATCCVR 16404TM) and Staphylococcus aureus (ATCCVR 6538TM). To perform the growth assay, trypticase soy agar (TSA) were used for P aeruginosa and S aureus, and sabouraud glucose agar (SAB) for C albicans and A brasiliensis. The test was performed by taking a 1:1000 dilution of 1 g of topical resorcinol in a 0.1% Tween 80 and phosphate buffered saline solution and adding 100 µL of a suspension equivalent to 1×103 cfu/mL of every ATCC strain, which were inoculated in TSA or SAB. All tests were done in duplicate and medium lectures were made in 48 hours. Results The ability of ATCC strains to growth in resorcinol formulation was confirmed under the study conditions. There was mean growth of 17×104 cfu/mL for S aureus and 11×104 cfu/mL for P aeruginosa in TSA. For A brasiliensis and C albicans, 1×104 cfu/mL and 2×104 cfu/mL were detected, respectively. Conclusion and relevance The presented method shows a simplified way to test the microbiological viability of 15% topical resorcinol for quality control. References and/or acknowledgements No conflict of interest.