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Abstract Background Ixodes ricinus ticks transmit Babesia species to vertebrate hosts. Using molecular tools we were able to detect the presence of this piroplasmid in its vector. The aims of this study were to investigate the prevalence and identity of Babesia species in questing ticks collected in various areas of Norway. Methods DNA from questing l. ricinus ticks were examined with a realtime PCR for the presence of Babesia. Positive samples of tick DNA were identified to species using PCR, and sequence analysis. Results From a total of 1908 questing l. ricinus ticks, 17 (0.9%) indicated the presence of Babesia spp. after realtime-PCR screening. Ixodes ricinus harbouring Babesia spp. was detected in 9 out of 22 localities. Further molecular analyses of DNA from these positive ticks indicate the presence of Babesia venatorum, B. divergens, B. capreoli and a currently undescribed Babesia in Norwegian ticks. The most prevalent was B. venatorum found in 71% of the positive ticks. Conclusions A total of 17 out of 1908 (0.9%) ticks were positive for Babesia. Our data confirm that there are several Babesia species in ticks in Norway. Babesia venatorum was the most prevalent. This species has a zoonotic potential and may cause human babesiosis following a tick bite.

Abstract Background Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum have been considered as pathogens in animals and humans. The role of wild cervids in the epidemiology is not clear. We analyzed questing Ixodes ricinus ticks collected in spring for these pathogens from sites with high (Fjelløyvær and Strøm) and low density (Tjore, Hinnebu and Jomfruland) of wild cervids to study the spread of the pathogens in questing ticks. Methods For detection of Anaplasma phagocytophilum a 77-bp fragment in the msp2 gene was used. Detection of Borrelia burgdorferi sensu lato was performed using the FL6 and FL7 primers according to sequences of conserved regions of the fla gene. The OspA gene located on the linear 49-kb plasmid was used as target in multiplex PCR for genotyping. Genospecies-specific primers were used in the PCR for Borrelia burgdorferi sensu stricto, B. afzelii and B. garinii. Results Infection rates with Borrelia spp. were significantly lower at Fjelløyvær and Strøm compared to Tjore and Hinnebu; Fjelløyvær vs. Tjore (χ2 = 20.27, p < 0.0001); Fjelløyvær vs. Hinnebu (χ2 = 24.04, p < 0.0001); Strøm vs. Tjore (χ2 = 11.47, p = 0.0007) and Strøm vs. Hinnebu (χ2 = 16.63, p < 0.0001). The Borrelia genospecies were dominated by. B. afzelii (82%) followed by B. garinii (9.7%) and B. burgdorferi sensu stricto (6.9%). B. burgdorferi s.s. was only found on the island of Jomfruland. The infection rate of Anaplasma phagocytophilum showed the following figures; Fjelløyvær vs Hinnebu (χ2 = 16.27, p = 0.0001); Strøm vs. Tjore (χ2 = 13.16, p = 0.0003); Strøm vs. Hinnebu (χ2 = 34.71, p < 0.0001); Fjelløyvær vs. Tjore (χ2 = 3.19, p = 0.0742) and Fjelløyvær vs. Støm (χ2 = 5.06, p = 0.0245). Wild cervids may serve as a reservoir for A. phagocytophilum. Jomfruland, with no wild cervids but high levels of migrating birds and rodents, harboured both B. burgdorferi s.l. and A. phagocytophilum in questing I. ricinus ticks. Birds and rodents may play an important role in maintaining the pathogens on Jomfruland. Conclusion The high abundance of roe deer and red deer on the Norwegian islands of Fjelløyvær and Strøm may reduce the infection rate of Borrelia burgdorferi sensu lato in host seeking Ixodes ricinus, in contrast to mainland sites at Hinnebu and Tjore with moderate abundance of wild cervids. The infection rate of Anaplasma phagocytophilum showed the opposite result with a high prevalence in questing ticks in localities with a high density of wild cervids compared to localities with lower density.

Copyright of Biologija is the property of Lithuanian Academy of Sciences Publishers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Birds are increasingly considered important in the global dispersal of tick-borne pathogens. The purpose of this study was to investigate the prevalence of Borrelia burgdorferi sensu lato genospecies in Ixodes ricinus ticks collected on passerine birds from two ornithological stations (Jomfruland and Lista) in southern Norway. In both sampling sites a total of 608 (109 larvae and 499 nymphs) of immature ticks were collected from 157 infested birds representing 26 species. The presence of B. burgdorferi s.l. DNA in ticks was tested using direct PCR amplification of the ospA gene, localized on lp-54 plasmid in B. burgdorferi s.l. genome. Twenty one out of 157 infested (13%) birds carried B. burgdorferi s.l. infected Ixodes ricinus ticks. B. burgdorferi s.l. DNA was detected in 19.7% of the tick samples. In total, 6.4% of larvae (7/109) and 10% of nymphs (50/499) were positive. The vast majority of infected ticks were found on blackbird (Turdus merula). The most frequent genospecies was B. garinii (85.5%), followed by B. afzelii (9.0%) and B. valaisiana (5.5%). Five different B. garinii genotypes were identified. Our findings showed that the blackbirds may support the circulation and spread of B. garinii and B. valaisiana. B. garinii was not detected in questing ticks from investigated locations. B. afzelii genospecies, however, dominated in questing ticks, rodents and ticks from rodents. [ABSTRACT FROM AUTHOR]

Norway represents the northern limit in the geographical distribution of Ixodes ricinus ticks in Europe. During the last decade an expansion of the range of this tick further north and at higher altitudes has been detected. This could affect the spread of Borrelia burgdorferi sensu lato pathogens in new territories and increase the risk of human infection in the country. The aim of the present study was to determine the prevalence of B. burgdorferi s.l. in I. ricinus ticks in different localities of Norway. Ticks were collected in 24 locations from northwest to southeast Norway during spring-summer 2004 and 2006-2008. We used fla gene as a target for amplification of spirochete DNA. Multiplex PCR based on ospA gene of B. burgdorferi s.l. was used for species identification. The heterogeneity of B. garinii strains was investigated using ospA-based sequencing analysis. B. burgdorferi s.l. was detected in 171 (7.2%) out of 2360 I. ricinus ticks analyzed. The infection rate varied from zero to 32% in the investigated locations. Infection rate in adults (11.9%) was significantly higher than in nymphs (4.7%). The overall infection rate in ticks from western Norway (4.0%) was significantly lower than in those from southern Norway (10%). Four B. burgdorferi s.l. genospecies were identified, and the most common was B. afzelii (71.9.0%), followed by B. garinii (12.9%), B. burgdorferi s.s. (7%) and B. valaisiana (1.2%). A total of eight (4.8%) of the infected ticks harboured mixed infections. Phylogenetic relationship between B. garinii strains and their correspondence to OspA serotype types was compared with the sequences registered in GenBank database. Five genotypes of B. garinii derived from ticks were identified. The most frequent was OspA type 6. [ABSTRACT FROM AUTHOR]

A total of 325 Listeria monocytogenes isolates from human, food and environmental sources were ribotyped with the Qualicon Automated Riboprinter Microbial Characterization System, using the enzyme EcoR1. The human isolates (n=137) represented all isolates from clinical cases in Norway from 1992 to 2005. The food and environmental isolates (n=188) were collected from different food related sources in Norway in the period 1989-2002. A total of 37 ribotypes were differentiated. Most common ribotypes (i.e., ribotypes represented by >5 isolates) were isolated from human as well as food and environmental sources. The exceptions were ribotypes DUP-1062D and 1058A, which were found only among food and environmental samples (14 and 5 times, respectively), and DUP-1042A, which was identified only among human clinical isolates. DUP-1030A, the most frequent ribotype among the human isolates, as well as ribotypes DUP-1042B, DUP-1042C, DUP-1049B and DUP-1062B were identified from both foods, environmental and human sources. DUP-1039C (n=54) and DUP-1045B (n=27) were frequently isolated from patients, food and environmental samples. The isolates were classified into lineages based on ribotyping results. The lineage I strain DUP-1038B was isolated every year from 1992 to 2005 from the human clinical samples. Out of 137 listeriosis cases, 76 (55.6%) were caused by lineage II strains. We found a considerable overlap between ribotypes, lineages and isolation sources. It does not seem possible to establish food strain specific regulations for L. monocytogenes based on ribotyping. [ABSTRACT FROM AUTHOR]

Copyright of Biologija is the property of Lithuanian Academy of Sciences Publishers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Campylobacteriosis is one of the most frequently occurring acute gastroenteritis in humans and 10% are caused by Campylobacter coli. A total of 136 isolates of C. coli from humans, poultry, and pigs were identified by multiplex polymerase chain reaction (PCR) and genetically characterized and compared by ribotyping. Automatic riboprints were performed with the PstI restriction enzyme and RiboPrinter®. All poultry, pig and human strains represented a heterogeneous spectre of ribotypes. Ten of 23 human strains (43%) could be given DUP-ID from the library represented by DUP-PSTI-1200 (n = 7), DUP-PST1-1201 (n = 2) and DUP-PSTI-1211 (n = 1). Eighteen of 28 (64%) poultry strains were given a DUP-ID. Three isolates were closely related to human strains DUP-PSTI-1201 (n = 2) and DUP-PSTI-1200 (n = 1) and may play an important role in the epidemiology of campylobacteriosis. Nineteen of 85 pig isolates (23%) could be given a DUP-ID, but none were common to human isolates. An overlap was found among poultry and pig isolates with DUP-PSTI-1182 and DUP-PSTI-1140. [ABSTRACT FROM AUTHOR]

Copyright of Estonian Journal of Ecology is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Biologija is the property of Lithuanian Academy of Sciences Publishers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Campylobacteriosis caused by Campylobacter jejuni, Campylobacter coli and Campylobacter lari is one of the most frequently occurring acute gastroenteritis diseases in humans. An important risk factor is untreated drinking water. Thermotolerant campylobacters were isolated from Bø River water using 100-ml filtrate samples. Campylobacters were isolated from 32 of 60 samples (53.3%). Of the 75 strains isolated, 47 (62.7%) were detected using the enrichment procedure and 28 (37.2%) by direct plating of the filter. Campylobacter coli was the dominating species (44%) followed by Campylobacter jejuni (34.6%) and Campylobacter lari (14.7%). Five isolates (6.7%) could not be classified. Campylobacter were isolated without the occurrence of fecal coliforms indicating that fecal coliforms cannot be used as index bacteria to predict the occurrence of campylobacters. Case-control studies have indicated untreated drinking water and barbecuing as important risk factors, and waterborne campylobacteriosis has been caused by the three species isolated. The virulence factors of isolated environmental strains are not fully known. It was concluded that it is hazardous to use untreated surface water for drinking. Special efforts should be taken to avoid contamination of agricultural products from irrigation. [ABSTRACT FROM AUTHOR]

Lyme borreliosis (LB) caused by the spirochete Borrelia burgdorferi s.l. is the most frequently diagnosed tick-bome zoonozis in Europe, North America, and Asia. B. burgdorferi s.l. can infect humans and wild and domestic animals. Small rodents are the most important reservoir host of B. burgdorferi s.l. The aim of present study was to detect f B. burgdorferi s.l. in different tissue samples of small rodents and identify Borrelia genospecies and strains using different molecular markers and detection methods. Flagellin (fla) and outer surface protein A (ospA) encoding genes of Borrelia genome were used as targets for PCR amplification. We found that the ospA gene was a more sensitive marker for the detection of B. burgdorferi s.l. than fla gene. The presence of B. burgdorferi s.l. in urinary bladder, spleen and ear biopsy samples of 136 small rodents was compared. B. burgdorferi s.l. infection was detected with different rates in ear and bladder tissues, but was not found in spleen samples. Multiplex PCR assay based on ospA gene was used for identifying B. burgdorferi s. s., B. afzelii, and B. garinii genospecies. B. afzelii was a single genospecies detected in small rodents from Norway and was predominant in rodents from Lithuania. B. garinii strains from rodents were identified by nucleotide sequencing of PCR products. Phylogenetic relationship between B. garinii strains and their correspondence to OspA serotype types were compared with the sequences registered in GenBank database. B. garinii strains detected in the present study showed similarities with sequences of OspA serotype 5 type and OspA serotype 6 type. [ABSTRACT FROM AUTHOR]

Five salmon processing plants were investigated for periods of eight (plants A and B) and four (plants C, D and E) months for the occurrence of Listeria monocytogenes. A total of 226 strains of L. monocytogenes were isolated and subtyped. Automated ribotyping with DuPont Qualicon RiboPrinter® system with the enzyme EcoR1 was used to differentiate and characterize isolates for simple molecular tracking. The isolated strains could be divided into 16 DuPont ribotypes. The ribotypes DUP-1023C, DUP-1039C, DUP-1044E, DUP-1045B, DUP-1046A, DUP-1062B and 1062C were found to be persistent in the plants, as they were found through the whole sampling period. The remaining 9 ribotypes were isolated sporadically. Five of the persistent subtypes (DUP-1023C, DUP-1039C, DUP-1046A, DUP-1062B and 1062C) where isolated in high numbers. Ribotype DUP-1045B and DUP-1039C were found in four of the five investigated plants. [ABSTRACT FROM AUTHOR]

The Gram-negative, obligate intracellular tick-transmitted pathogen Anaplasma phagocytophilum can cause acute febrile diseases in humans and domestic animals. The expansion of the tick Ixodes ricinus (Linnaeus, 1758) in northern Europe due to climate change is of serious concern for animal and human health. The aim of the present study was to investigate the impact of A. phagocytophilum infection in moose Alces alces (Linnaeus) calves by evaluating the carcass weights of infected and non-infected animals and examining animal tissues samples for co-infections with either species of Babesia Starcovici, 1893 or bacteria of the genus Bartonella. The carcasses of 68 free-ranging moose calves were weighed by hunters during the hunting seasons from 2014 to 2017 in two regions in southern Norway and spleen samples were collected. Anaplasma phagocytophilum was detected in moose sampled from locations infected with ticks with a prevalence of 82% (n = 46). The carcass weights of A. phagocytophilum-infected calves (n = 46) and non-infected (n = 22) calves were compared. Although the average weight of infected calves (45.6 kg) was lower than that of non-infected calves (46.5 kg), the difference was not statistically significant. Three different variants of the bacterium 16S rRNA gene were identified. The average weight of animals infected with variant I was 49.9 kg, whereas that of animals infected with variant III was 42.0 kg, but the difference was not statistically significant (p = 0.077). Co-infections of A. phagocytophilum with Bartonella spp. or with Babesia spp. were found in 20 and two calves, respectively. A triple infection was found in two calves. Sequence analysis of the 18S rRNA gene of Babesia-positive samples revealed the presence of Babesia cf. odocoilei (Emerson et Wright, 1970). Strains of Bartonella closely related to Bartonella bovis (Bermond, Boulouis, Heller, Laere, Monteil, Chomel, Sander, Dehio et Piemont, 2002) were identified based on phylogenetic analysis of the gltA and rpoB genes. The loss of body mass in moose calves in the tick-infected site was probably influenced by multiple factors.

Babesiosis is an emerging zoonotic disease and various wildlife species are reservoir hosts for zoonotic species of Babesia Starcovici, 1893. The objective of the present study was to investigate the presence and prevalence of Babesia spp. in moose Alces alces (Linnaeus) in two regions of Norway. A total of 99 spleen samples were collected from animals of various ages from an area with the occurrence of the tick Ixodes ricinus (Linnaeus, 1758), and from an area where the ticks are known to be absent. Infection was detected by the amplification of different regions of the 18S rRNA gene by using two different PCR primer sets specific of Babesia. Babesia spp. were found in the spleen samples of four moose. All Babesia-infected animals were from an area where ticks occur, with an infection rate of 6% (4 of 70). Babesia-positive samples were obtained from a five-month old moose calf and three adults. Two Babesia species, Babesia capreoli (Enigk et Friedhoff, 1962) and a B. odocoilei-like, were identified. Co-infection with Anaplasma phagocytophilum was obtained in two animals. This is the first report of the occurrence of B. capreoli and B. odocoilei-like species in moose.

Background: Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum have been considered as pathogens in animals and humans. The role of wild cervids in the epidemiology is not clear. We analyzed questing Ixodes ricinus ticks collected in spring for these pathogens from sites with high (Fjelløyvaer and Strøm) and low density (Tjore, Hinnebu and Jomfruland) of wild cervids to study the spread of the pathogens in questing ticks., Methods: For detection of Anaplasma phagocytophilum a 77-bp fragment in the msp2 gene was used. Detection of Borrelia burgdorferi sensu lato was performed using the FL6 and FL7 primers according to sequences of conserved regions of the fla gene. The OspA gene located on the linear 49-kb plasmid was used as target in multiplex PCR for genotyping. Genospecies-specific primers were used in the PCR for Borrelia burgdorferi sensu stricto, B. afzelii and B. garinii., Results: Infection rates with Borrelia spp. were significantly lower at Fjelløyvaer and Strøm compared to Tjore and Hinnebu; Fjelløyvaer vs. Tjore (chi2 = 20.27, p < 0.0001); Fjelløyvaer vs. Hinnebu (chi2 = 24.04, p < 0.0001); Strøm vs. Tjore (chi2 = 11.47, p = 0.0007) and Strøm vs. Hinnebu (chi2 = 16.63, p < 0.0001). The Borrelia genospecies were dominated by. B. afzelii (82%) followed by B. garinii (9.7%) and B. burgdorferi sensu stricto (6.9%). B. burgdorferi s.s. was only found on the island of Jomfruland. The infection rate of Anaplasma phagocytophilum showed the following figures; Fjelløyvaer vs Hinnebu (chi2 = 16.27, p = 0.0001); Strøm vs. Tjore (chi2 = 13.16, p = 0.0003); Strøm vs. Hinnebu (chi2 = 34.71, p < 0.0001); Fjelløyvaer vs. Tjore (chi2 = 3.19, p = 0.0742) and Fjelløyvaer vs. Støm (chi2 = 5.06, p = 0.0245). Wild cervids may serve as a reservoir for A. phagocytophilum. Jomfruland, with no wild cervids but high levels of migrating birds and rodents, harboured both B. burgdorferi s.l. and A. phagocytophilum in questing I. ricinus ticks. Birds and rodents may play an important role in maintaining the pathogens on Jomfruland., Conclusion: The high abundance of roe deer and red deer on the Norwegian islands of Fjelløyvaer and Strøm may reduce the infection rate of Borrelia burgdorferi sensu lato in host seeking Ixodes ricinus, in contrast to mainland sites at Hinnebu and Tjore with moderate abundance of wild cervids. The infection rate of Anaplasma phagocytophilum showed the opposite result with a high prevalence in questing ticks in localities with a high density of wild cervids compared to localities with lower density.

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.

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.

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.