Similarity of Campylobacter lari among human, animal, and water isolates in Norway.

A total of 49 isolates of Campylobacter lari from human, poultry, ducks, pigs, and water were genetically characterized. The species were identified by biotyping and multiplex polymerase chain reaction (PCR). Automatic riboprints were performed with the PstI restriction enzyme and RiboPrinter. The identification of the isolates was predicted when the corresponding pattern matched one of the patterns of the DuPont identification (DUP-ID) library and was then assigned an identification number. Thirty-five (71.4%) of the isolates were given a DUP-ID number. The isolates from water and animals showed a high degree of similarity to the human strains represented by DUP-PST1-1010, DUP-PST1-1166, DUP-PST1-1178, and DUP-PST1-1081. Some profiles (i.e., DUP-PST1-2021 and DUP-PST1-1184) were found only among the human isolates. Dendrogram analysis using BioNumerics grouped isolates into three main clusters. One of those clusters contained DUP-PST1-2021, DUP-PST1-1184, and DUP-PST1-1081, which was found in both humans and ducks. A second cluster generated DUP-PST1-1010, found in both humans and poultry, and DUP-PST1-1079, found in water. The third cluster consisted of two strains, DUP-PST1-1066 and DUP-PST1-1078, originating in humans, animals, and water. Three human strains and two poultry strains were diverse and formed their own clusters and could not be assigned a DUP-ID number. Because of the similarity of C. lari isolated from humans, poultry, ducks, pigs, and water, as well as the limited knowledge of environmental survival and its virulence factors, special hygienic precautions should be taken to avoid the risk of transmitting Campylobacter.

Ribotype diversity of Listeria monocytogenes isolates from two salmon processing plants in Norway.

The purpose of this study was to use automated ribotyping procedure to track Listeria monocytogenes transmission in the cold smoked fish production chain and to characterize L. monocytogenes subtypes associated with the salmon processing industry. A total of 104 isolates, which had previously been obtained from a raw fish slaughter and processing plant (plant B) and an adjacent, downstream, salmon smoking operation (plant A), were characterized. These isolates had been obtained through a longitudinal study on Listeria presence, which covered a 31-week period, in both plants. Isolates had been obtained from samples taken from different machinery used throughout the production process. In addition, six isolates obtained from products produced in plant A two years after the initial study were included, so that a total of 110 isolates were characterized. Automated ribotyping was performed using both the restriction enzymes EcoRI and PvuII to increase the discriminatory power. The 110 L. monocytogenes isolates could be divided into 11 EcoRI ribotypes; PvuII ribotype data yielded multiple subtypes within 7 EcoRI ribotypes for a total of 21 subtypes based on both EcoRI and PvuII ribotyping. A total of three EcoRI ribotypes (DUP-1023C, DUP-1045B, and DUP-1053E) were isolated at multiple sampling times from both plants. In addition, one subtype (DUP-1053B) was isolated at multiple sampling times in only plant A, the salmon smoking operation. These data not only support that L. monocytogenes can persist throughout the salmon production system, but also showed that L. monocytogenes may be transmitted between slaughter and smoking operations or may be unique to smoking operations. While the majority of subtypes isolated have been rarely or never linked to human listeriosis cases, some subtypes have previously caused human listeriosis outbreaks and cases. Molecular subtyping thus is critical to identify L. monocytogenes transmission and niches in order to allow design and implementation of control strategies at the appropriate stage of production and in order to reduce the prevalence of L. monocytogenes linked to human disease.

Longitudinal studies on Listeria monocytogenes and other Listeria species in two salmon processing plants.

Two plants processing salmon fillets and cold smoked salmon were investigated for occurrence of Listeria in products and the environment. Analyses were conducted for a period of 31 weeks. At plant A, 252 samples were examined of which 97 were from unprocessed fish and 155 from cold-smoked fish. At plant B, 189 samples of unprocessed fish were investigated. The first examination of unprocessed fish at plant A showed a presence of L. monocytogenes and L. spp. in 81% and 19% of the samples respectively. For cold-smoked fish the figures were 43% and 23%. At plant B, L. monocytogenes was isolated in 63% of the samples. During the test period, management at the processing plant initiated various hygiene precautions to improve the sanitary situation. The last batch of analyses of unprocessed fish at plant A showed a presence of L. monocytogenes and L. spp. in 42% and. 33% of the samples respectively. For cold-smoked fish, the figures were 6% and 11%. The isolation figures at plant B for L. monocytogenes and L. spp. were 50% and 17% respectively. The hygienic precautions did not have a significant effect on the presence of L. monocytogenes and L. spp. We suggest that Listeria bacteria are a part of the resident flora and are not eliminated by current cleaning and sanitation programmes. Cold-smoking, however, gave a significant reduction in the isolation of L. monocytogenes (P = 0.0082), while the isolation of L. spp. did not decrease after this process.