RESUMO
AIMS: The aims of this study were to characterize the genetic diversity of Listeria monocytogenes isolates obtained from commercial mushroom production, to establish the persistence, recontamination and the risk of cross-contamination from the working environment to the final products, creating awareness about the presence of L. monocytogenes thus helping to prevent the possibility of cross-contamination. METHODS AND RESULTS: From an extensive analysis of commercial mushroom production, analysed with BS EN ISO 11290-1:1996/Amd 1:2004 and BS EN ISO 11290-2:1998/Amd 1:2004, 279 L. monocytogenes isolates were obtained. All of the isolates were characterized by pulsed-field gel electrophoresis, species PCR and serogroup PCR. All the isolates were confirmed as L. monocytogenes; 30·1% were serogroup 1/2b-3b-7, 40·8% were serogroup 1/2a-3a and 29·1% were serogroup 4b-4d-4e. There were 77 pulsotypes from the 279 isolates, 40 of the pulsotypes had only one strain and 37 had two or more strains, indicating great diversity in the isolates. CONCLUSIONS: The high genetic diversity is indicative of the fact that current hygiene practices are successful at removing L. monocytogenes but that recontamination of the production environment is frequent. SIGNIFICANCE AND IMPACT OF THE STUDY: The results obtained are very valuable in creating awareness of L. monocytogenes in mushroom production and for the improvement of hygiene practices.