Use of a microbial toxicity test (Microtox Ò ) to determine the toxigenicity of Aspergillus fumigatus strains isolated from different sources Patricia Alba a , Sebastia ´n Sa ´ nchez-Fortu ´n b , Sergio Alvarez-Perez a , Jose L. Blanco a, * , Marta E. Garcı ´a a a Departamento Sanidad Animal, Facultad de Veterinaria, Universidad Complutense, Avda Puerta de Hierro s/n, 28040 Madrid, Spain b Departamento Toxicologı ´a y Farmacologı ´a, Facultad de Veterinaria, UCM, Spain article info Article history: Received 8 January 2009 Received in revised form 6 February 2009 Accepted 11 February 2009 Available online 21 February 2009 Keywords: Aspergillus fumigatus Mycotoxin Bioassay Microtox Invasiveness abstract The toxic activity of Aspergillus fumigatus is attributable to substances secreted by its cells. Specific toxic compounds synthesized by the fungi such as gliotoxin, can be detected by sensitive chemical procedures like TLC or HPLC. Measuring the total toxigenicity of a strain extract, however, requires a bioassay. In the present study, we evaluated the possibility of using the Microtox Ò bioassay to determine the toxigenicity of A. fumigatus, using 32 strains from different sources. The Microtox Ò method is based on the ability of Vibrio fischeri to produce luminescence, and their sensitivity to toxins. A. fumigatus strains, grouped according to their original sources, showed differences in toxigenicity. Strains isolated from invasive aspergillosis patients proved to be more toxigenic than environmental strains, or strains from colonized patients. Since the strains that were more toxigenic were isolated from sick patients, it is not surprising they showed more virulence than the other strains, and as expected, virulence could be correlated with high toxigenicity. The Microtox bioassay could be a useful tool in the study of toxigenicity of the mycelial fungi and their possible pathogenic roles, and for rapid assessment of secreted toxic compounds. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Aspergillus fumigatus is a ubiquitous mycelial fungus that can cause various infections in human and animals, among which invasive aspergillosis (IA) is the most important because of a high mortality rate in immuno- suppressed patients (Latge ´, 1999; Lumbreras and Gavalda `, 2003). Pathogenicity factors involved in IA development are not completely defined (Latge ´, 1999; Tomee and Kauffman, 2000), although hypotheses have been proposed about the role of mycotoxin production in the establish- ment of illness (Sutton et al., 1996; Nieminen et al., 2002; Watanabe et al., 2004b; Kamei and Watanabe, 2005; Sugui et al., 2007). Although gliotoxin could be the most important mycotoxin produced by A. fumigatus because of its immunosuppressing activity (Murayama et al., 1996; Watanabe et al., 2003), its effect is known to be reinforced by other secondary metabolites, most of which are not yet characterized (Watanabe et al., 2003). Therefore, fungal toxic activity must be viewed in the context of all the secreted substances that are present in the substrate where the fungus grows (Rementerı ´a et al., 2006). Sensitive chemical procedures, like TLC or HPLC, can detect specific toxic compounds. If every toxic compound is not known, however, bioassays are more informative. Traditional acute toxicity bioassays using multi-cellular organisms are time-consuming, requiring lengthy exposure periods of up to 96 h. In contrast, microbial toxicity tests, such as the Microtox Ò Test, take no more than 45 min to conduct, and can measure temporal changes in bioavail- ability over relatively short time frames (Kaiser and * Corresponding author. Tel.: þ34 913943717; fax: þ34 913943908. E-mail address: jlblanco@vet.ucm.es (J.L. Blanco). Contents lists available at ScienceDirect Toxicon journal homepage: www.elsevier.com/locate/toxicon 0041-0101/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.toxicon.2009.02.009 Toxicon 53 (2009) 729–733