Genotypic characterization of Brochothrix thermosphacta isolated during storage of minced pork under aerobic or modified atmosphere packaging conditions

A total of 306 colonies were isolated from the selective medium for Brochothrix spp., during the spoilage of minced pork stored at 0, 5, 10 and 15 °C and packed aerobically and under modified atmosphere packaging conditions (MAP). Brochothrix biodiversity was assessed by Pulsed Field Gel Electrophoresis (PFGE), and representative strains were further analysed by Rep-PCR using primer (GTG)5 and Sau-PCR with primers SAG1and SAG2. Although, different results were obtained from the different methods, a significant diversity among isolates recovered from aerobic conditions was observed. On the contrary, isolates from MAP showed a lower degree of heterogeneity. The storage conditions affected the Brochothrix diversity, the strains isolated in the initial stage being different from the ones present at the final stage of storage at chill temperatures. A representative number of isolates, based on the results of the clustering by molecular methods, were subjected to 16S rRNA gene sequencing, revealing that all belonged to Brochothrix thermosphacta.