Specific detection of Stenotrophomonas maltophilia strains in albacore tuna (Thunnus alalunga) by reverse dot-blot hybridization

A reverse dot-blot DNA/DNA hybridization method coupled with a non-radioactive nucleic acid detection system was evaluated for the direct detection of the emerging pathogen Stenotrophomonas maltophilia in albacore tuna, a fish species of high commercial value in Europe and the US. Probes consisting of total genomic DNA of S. maltophilia, when used in dot-blot hybridization assays, differed in a sufficient way with respect to Morganella morganii, Enterobacter aerogenes Enterobacter agglomerans, Klebsiella planticola, Acinetobacter baumani and other bacteria frequently isolated from spoiled tuna fish species, as to allow its specific detection in extracts of albacore tuna. The introduction of an enrichment step prior to DNA isolation and labelling allowed the successful detection of 102 viable cells of S. maltophilia in 1 ml of artificially-contaminated albacore muscle extracts with no cross-hybridization with other Gram-negative competing microflora being observed. The detection strategy described in this work may be useful for the detection and control of S. maltophilia in tuna fish species and seafood products.