Occurrence, antimicrobial resistance, and genetic diversity of Listeria monocytogenes at fish-processing plants in Vietnam

In this study, the occurrence, serogroups, virulence genes, antibiotic susceptibility profiles, and diversity were estimated for Listeria monocytogenes isolated from Pangasius fish in two processing facilities in Vietnam. L. monocytogenes was most frequently detected in wash water samples at 20.8 % (15 out of 72), and in Pangasius fish it was 16.6 % (15 out of 90 fish samples). Serotypes 1/2b were dominant, and internalin genes (inlA, inlC, and inlJ) were found in all the L. monocytogenes isolates. Most of the isolates were resistant to cefoxitin, oxacillin, and fosfomycin. Genotyping of L. monocytogenes by random amplified polymorphic DNA analysis revealed three clusters of the isolates specific to the facilities to some extent. This study suggests a high risk of L. monocytogenes contamination from wash water to fish. Hence, maintaining the quality of water and designing sanitation procedures to reduce L. monocytogenes contamination are required to ensure food safety at Pangasius fish processing plants.