Tracing Listeria monocytogenes isolates from cold-smoked salmon and its processing environment in Iceland using pulsed-field gel electrophoresis

• Published in: International journal of food microbiology Vol. 101; no. 1; pp. 41 - 51
• Main Authors: Gudmundsdóttir, Sigrún, Gudbjörnsdóttir, Birna, Lauzon, Hélène L., Einarsson, Hjörleifur, Kristinsson, Karl G., Kristjánsson, Már
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-05-2005; Elsevier
• Subjects: Animals; bacterial contamination; Biological and medical sciences; Cold-smoked salmon; Contamination; DNA, Bacterial - genetics; DNA, Bacterial - isolation & purification; Electrophoresis, Gel, Pulsed-Field - methods; Environmental Microbiology; Fish and seafood industries; fish processing; food contamination; Food Contamination - analysis; Food Handling - methods; Food Handling - standards; Food industries; Food microbiology; food pathogens; food processing equipment; food processing plants; Food-Processing Industry - standards; Fundamental and applied biological sciences. Psychology; genotype; human resources; Iceland; Incidence; Listeria monocytogenes; Listeria monocytogenes - isolation & purification; microbial detection; PFGE; processing stages; pulsed-field gel electrophoresis; raw fish; raw materials; salmon; Salmon - microbiology; Salmonidae; Seafood - microbiology; serotypes; Serotyping; smoked fish; traceability; Iceland; Atlantic Ocean Islands; Listeria monocytogenes; PFGE; Contamination; Cold-smoked salmon; Edible fish; Pulsed field electrophoresis; Cold; Salmon; Bacteria; Environment; Isolate
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2004.08.023

Listeria spp. and
Listeria monocytogenes contamination of cold-smoked salmon (
n=125) and its processing environment (
n=522) were evaluated during surveys conducted in 1997–1998 and 2001 as well as in samples of final products analysed in 2001. The overall frequencies of
Listeria spp. and
L. monocytogenes in samples from all sources were 15.1% and 11.3%, respectively, but the incidence of
L. monocytogenes in cold-smoked salmon final products was only 4%. A total of 201
L. monocytogenes isolates were characterised by Pulsed-Field Gel Electrophoresis (PFGE) in order to trace
L. monocytogenes contamination in the processing plants. The combination of
AscI and
ApaI macrorestriction patterns yielded 24 different pulsotypes in 6 plants. One pulsotype observed by
AscI restriction digestion comprised 148 of the 167 typed isolates from two processing plants. Two other pulsotypes predominated in samples from raw material, processing environments and final products. The results indicate that raw material, floors, and drains are potential sources of the
L. monocytogenes found on cold-smoked salmon products. This highlights the need to readdress the design and cleaning of processing plants and equipment, and staff behavior. Hindering the introduction into and spread of the organism through the processing environment is necessary to avoid jeopardizing safety of the final product.