Prevalence and Contamination Patterns of Listeria monocytogenes in Fresh Catfish Fillets and their Processing Plants

Authors: CHEN, B - Mississippi State University; PYLA, R - Mississippi State University; KIM, T - Mississippi State University; SILVA, J - Mississippi State University; JUNG, Y - Mississippi State University

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2010
Publication Date: 3/9/2010
Citation: Chen, B.Y., Pyla, R., Kim, T.J., Silva, J.L., Jung, Y.U. 2010. Prevalence and Contamination Patterns of Listeria monocytogenes in Fresh Catfish Fillets and their Processing Plants. Food Microbiology. 27:645-652.

Interpretive Summary: It is well known that Listeria monocytogenes (Lm) is an environmental pathogen, but also it is found in catfish. This study showed that the main source of Lm in catfish plants is environmental. This can lead to development of technologies and steps to better rid plants from Lm so as to produce products with lower incidence of Lm.

Technical Abstract: Catfish skins, intestines, fresh fillets, processing surfaces at different production stages, chiller water and non-food contact surfaces were sampled for Listeria monocytogenes and other Listeria species. Among 315 samples, prevalence of L. monocytogenes, Listeria innocua and a group of Listeria seeligeri–Listeria welshimeri–Listeria ivanovii was 21.6, 13.0 and 29.5%, respectively. No Listeria grayi was detected in this survey. While no L. monocytogenes strains were isolated from catfish skins and intestines, the strains were found with a frequency of 76.7% in chilled fresh catfish fillets and 43.3% in unchilled fillets. L. monocytogenes and Listeria spp. were also detected in fish contact surfaces such as deheading machine, trimming board, chiller water, conveyor belts at different stages, and fillet weighing table. Among L. monocytogenes, 1/2b (47.0%), 3b (16.0%) and 4c (14%) were the predominant serotypes isolated, whereas 4b, 4e, 1/2c and 1/2a were detected at much lower frequencies. Genotype analyses of L. monocytogenes isolates using serotyping, pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus (ERIC)-PCR revealed that chiller water represented an important contamination source of L. monocytogenes in the chilled catfish fillets of two processing facilities, whereas fillet weighing table significantly contributed to the catfish fillet contamination of the third facility. This study suggests that L. monocytogenes contamination in the processed catfish fillets originates from the processing environment, rather than directly from catfish. Results from this study can aid the catfish industry to develop a plant-specific proper cleaning and sanitation procedure for equipment and the processing environment designed to specifically target L. monocytogenes contamination.