An evaluation of the suitability of the European suspension test to reflect in vitro activity of antiseptics against clinically significant organisms

The effectiveness of four antiseptics representing soluble phenolics (Detto l), Quaternary Ammonium Compounds (QAC) (Dettol Hospital Concentrate: DHC), mixed QAC/chlorhexidine (Hibicet Hospital Concentrate: HHC) and povidone i odine (Betadine) was assessed using the proposed phase 2 step 1 European Su spension test. The in vitro activity of the antiseptics against two of the proposed challenge strains, i.e. Staphylococcus aureus and Pseudomonas aeru ginosa, was compared with that of 14 problematic clinical isolates of bacte ria from a range of genera, including some multiple antibiotic resistant st rains, and a clinical isolate of Candida albicans. In addition to the 5 min contact time recommended in the European test, a 1 min time was included. All four products, at their recommended use dilutions and a contact time of 5 min, achieved a Microbicidal Effect (ME) log reduction of at least 5 aga inst the majority of organisms. Differences in activity between products we re more pronounced and therefore the tests more discriminatory, when the co ntact time was reduced to 1 min. The clinical strains were not overtly more resistant to antiseptics than the standard test strains, suggesting that t he CEN test strains mimic the antiseptic susceptibility of clinical isolate s.