In vitro testing of fungicidal activity of biocides against Aspergillus fumigatus

The activity of biocides against Aspergillus fumigatus is unknown. In the European guidelines to evaluate the fungicidal activity of a biocide (EN 1275, 1997) the critical step concerning the preparation of conidia suspension is cumbersome and time consuming. The aims of the study were to evaluate a simplified procedure to prepare conidia suspensions to test a biocide in comparison with the recommended one and to investigate the in vitro activity of seven biocides by the suspension-neutralisation method against A.fumigatus clinical isolates. The proposed simplified procedure proved reproducible, gave the same results and was quicker than that described in the European guidelines. Benzalkonium chloride (0.25%), glutaraldehyde (1.6%), polyvinylpyrrolidone iodine (1% available I), polyesther glycol iodine (0.18% available I) showed cidal activity in ≤ 5 min contact time, chlorine (0.14% available Cl) and chlorhexidine (0.06%) after 15 min and 30-60 min, respectively. On the contrary chloramine T (0.01%) did not show any activity. In addition, a simplified and reproducible procedure may be adopted for testing the fungicidal activity of new compounds or combined formulations. In conclusion the mostly used products have been shown to display cidal activity against A.fumigatus and a simplified procedure may be adopted for testing the fungicidal activity of new compounds