| 1. |
- Tham, Wilhem, 1951-, et al.
(author)
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Occurrence of Genetic Variants of Listeria monocytogenes Strains
- 2013
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In: Foodborne pathogens and disease. - : Mary Ann Liebert. - 1535-3141 .- 1556-7125. ; 10:9, s. 825-826
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Journal article (peer-reviewed)abstract
- Isolates of Listeria monocytogenes saved from outbreaks of listeriosis, cases of sporadic listeriosis, and similar events do not always belong to a solitary genetic variant. Variants of the same strain may have evolved from a unique clone, and plasmid loss or gain and phage-mediated genetic changes are suggested as the main mechanism. Some of these reports are summarized in this short communication.
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| 2. |
- Lopez-Valladares, Gloria, 1963-, et al.
(author)
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Division of Human Listeria monocytogenes Pulsed-Field Gel Electrophoresis (PFGE) Types Belonging to Lineage I (Serovar 4b, 1/2b, and 3b) into PFGE Groups
- 2015
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In: Foodborne pathogens and disease. - : Mary Ann Liebert. - 1535-3141 .- 1556-7125. ; 12:5, s. 447-453
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Journal article (peer-reviewed)abstract
- The 63 pulsed-field gel electrophoresis (PFGE) types identified among 427 clinical isolates of Listeria monocytogenes that were characterized in a previous study by serotyping and PFGE (AscI) could be further divided into 17 PFGE groups. While the 63 PFGE types, all part of lineage I, were established based on the number and distribution of all bands in each DNA profile, the 17 PFGE groups were based on the configuration of small bands with sizes L. monocytogenes serovar 4b isolates (n=334) were divided into 8 PFGE groups; the 32 PFGE types of serovar 1/2b isolates (n=90) and the serovar 3b isolates (n=3, 1 PFGE type) were divided into 9 PFGE groups. An association was observed between PFGE groups and serovars. L. monocytogenes isolates belonging to PFGE groups I, J, Q, R, X, Z, o-4, and o-5 all shared serovar 4b, whereas isolates from PFGE groups D, G, O, P, T, U, o-1, o-2, and o-3 shared serovar 1/2b. Small fragments L. monocytogenes isolates. From the results of the present study, a procedure for accelerating the identification of PFGE types when analyzing new PFGE profiles can be suggested. Therefore, we propose a stepwise procedure to PFGE profiling by first identifying the PFGE group using the smaller band patterns <145.5 kb, and then determining PFGE types based on the band patterns >145.5 kb.
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| 3. |
- Lopez-Valladares, Gloria, 1963-, et al.
(author)
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Human isolates of Listeria monocytogenes in Sweden during half a century (1958-2010)
- 2014
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In: Epidemiology and Infection. - 0950-2688 .- 1469-4409. ; 142, s. 2251-2260
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Journal article (peer-reviewed)abstract
- Isolates of Listeria monocytogenes (n=932) isolated in Sweden during 1958–2010 from human patients with invasive listeriosis were characterized by serotyping and pulsed-field gel electrophoresis (PFGE) (AscI). Of the 932 isolates, 183 different PFGE types were identified, of which 83 were each represented by only one isolate. In all, 483 serovar 1/2a isolates were distributed over 114 PFGE types; 90 serovar 1/2b isolates gave 32 PFGE types; 21 serovar 1/2c isolates gave nine PFGE types; three serovar 3b isolates gave one PFGE type; and, 335 serovar 4b isolates gave 31 PFGE types. During the 1980s in Sweden, several serovar 4b cases were associated with the consumption of European raw soft cheese. However, as cheese-production hygiene has improved, the number of 4b cases has decreased. Since 1996, serovar 1/2a has been the dominant L. monocytogenes serovar in human listeriosis in Sweden. Therefore, based on current serovars and PFGE types, an association between human cases of listeriosis and the consumption of vacuum-packed gravad and cold-smoked salmon is suggested.
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| 4. |
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| 5. |
- Lopez-Valladares, Gloria, 1963-, et al.
(author)
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Implicated food products for listeriosis and changes in serovars of Listeria monocytogenes affecting humans in recent decades
- 2018
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In: Foodborne pathogens and disease. - : Mary Ann Liebert. - 1535-3141 .- 1556-7125. ; 15:7, s. 387-397
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Journal article (peer-reviewed)abstract
- Listeriosis is a foodborne disease with a high fatality rate, and infection is mostly transmitted through ready-toeat(RTE) foods contaminated with Listeria monocytogenes, such as gravad/smoked fish, soft cheeses, andsliced processed delicatessen (deli) meat. Food products/dishes stored in vacuum or in modified atmospheresand with extended refrigerator shelf lives provide an opportunity for L. monocytogenes to multiply to largenumbers toward the end of the shelf life. Elderly, pregnant women, neonates, and immunocompromisedindividuals are particularly susceptible to L. monocytogenes. Listeriosis in humans manifests primarily assepticemia, meningitis, encephalitis, gastrointestinal infection, and abortion. In the mid 1990s and early 2000s ashift from L. monocytogenes serovar 4b to serovar 1/2a causing human listeriosis occurred, and serovar 1/2a isbecoming more frequently linked to outbreaks of listeriosis, particularly in Europe and Northern America.Consumer lifestyle has changed, and less time is available for food preparation. Modern lifestyle has markedlychanged eating habits worldwide, with a consequent increased demand for RTE foods; therefore, more RTE andtake away foods are consumed. There is a concern that many Listeria outbreaks are reported from hospitals.Therefore, it is vitally important that foods (especially cooked and chilled) delivered to hospitals and residentialhomes for senior citizens and elderly people are reheated to at least 72C: cold food, such as turkey deli meatand cold-smoked and gravad salmon should be free from L. monocytogenes. Several countries have zerotolerance for RTE foods that support the growth of Listeria.
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| 6. |
- Lopez-Valladares, Gloria, 1963-, et al.
(author)
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Lineage II (Serovar 1/2a and 1/2c) Human Listeria monocytogenes Pulsed-Field Gel Electrophoresis Types Divided into PFGE Groups Using the Band Patterns Below 145.5 kb
- 2017
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In: Foodborne pathogens and disease. - New Rochelle, USA : Mary Ann Liebert. - 1535-3141 .- 1556-7125. ; 14:1, s. 8-16
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Journal article (peer-reviewed)abstract
- Among 504 clinical lineage II isolates of Listeria monocytogenes isolated during 1958-2010 in Sweden, 119 pulsed-field gel electrophoresis (PFGE) types (AscI) have been identified based on the number and distribution of all banding patterns in each DNA profile. In this study, these types were further divided into PFGE groups based on the configuration of small bands with sizes <145.5 kb. The 504 isolates included 483 serovar 1/2a isolates distributed into 114 PFGE types and 21 serovar 1/2c isolates distributed into 9 PFGE types; these were further divided into 21 PFGE groups. PFGE group, that is, configuration of small bands below 145.5 kb, and serovars were correlated. L. monocytogenes isolates belonging to PFGE groups A, B, C, E, F, H, K, L, M, S, V, W, Y, and Ö-6 to Ö-12 shared serovar 1/2a, with one exception. PFGE group E also included two PFGE types sharing serovar 1/2c and four PFGE types belonging to either serovar 1/2a or 1/2c. Isolates belonging to PFGE group N shared serovar 1/2c. In contrast to lineage I isolates, small fragments <33.3 kb were visible in all L. monocytogenes isolates belonging to lineage II. In the results from both the present and previous studies, the genomic region of small bands was genetically more conservative than in large bands. The distribution of these small bands established the relatedness of strains and defined a genetic marker for both lineages I and II, while also establishing their serogroup. The division of L. monocytogenes PFGE types into PFGE groups is advantageous as the profile of every new isolate can be identified easily and quickly through first studying the PFGE group affiliation of the isolate based on the smaller band patterns <145.5 kb, and then identifying the PFGE type based on the band patterns >145.5 kb.
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| 7. |
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| 8. |
- Lopez-Valladares, Gloria, 1963-, et al.
(author)
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Listeriosis in South American camelids : a review
- 2013
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In: Journal of Camel Practice and Research. - : Camel Publ House. - 0971-6777 .- 2277-8934. ; 20:1, s. 129-132
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Research review (peer-reviewed)abstract
- The main aim of the present study was to review the general aspects of Listeria and the clinical manifestation of the disease listeriosis in humans and domestic ruminants, with emphasis on clinical signs in South American camelids. Camelids are susceptible to infection by Listeria; however, it appears that the prevalence of listeriosis in camelids is low, given that few cases have been reported. The species Listeria monocytogenes is associated with all reported cases. To our knowledge, there are no reported cases of listeriosis in vicunas (Vicugna vicugna) and guanacos (Lama guanicoe).The clinical manifestations of listeriosis in llamas and alpacas are similar to in domestic ruminants and humans, namely meningoencephalitis, encephalitis, septicaemia, abortion, otitis media/interna and polyarthritis. Listerial mastitis and gastroenteritis has not yet been described in camelids. Despite reported cases, there is no specific mention of listeriosis associated with shedding of bacteria in faeces or milk. The occurrence of listeriosis in camelids needs to be confirmed and clinical signs defined.
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| 9. |
- Parihar, Vishal Singh, et al.
(author)
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Characterization of human invasive isolates of Listeria monocytogenes in Sweden 1986-2007
- 2008
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In: Foodborne pathogens and disease. - : Mary Ann Liebert. - 1535-3141 .- 1556-7125. ; 5:6, s. 755-761
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Journal article (peer-reviewed)abstract
- Since 1986, 68% of the Listeria monocytogenes isolates from human cases of invasive listeriosis in Sweden are available for retrospective studies. The aim of the present study was to characterize 601 human invasive isolates of L. monocytogenes in Sweden from 1986 to 2007 by using serotyping and pulsed-field gel electrophoresis. Since 1996, serovar 4b was permanently reduced to the second or third most common serovar in human cases in Sweden. During the latter period, 2000-2007, only 13% belonged to serovar 4b and 71% to 1/2a. The dendrogram, based on pulsovars, reveals two clusters with different serovars. Cluster 1 exhibits serovars 4b and 1/2b, whereas cluster 2 consists of serovar 1/2a. Serovar 1/2a seems to be more heterogeneous than serovar 4b.
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| 10. |
- Tham, Wilhelm, 1951-, et al.
(author)
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More than one variant of Listeria monocytogenes isolated from each of two human cases of invasive listeriosis
- 2007
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In: Epidemiology and Infection. - 0950-2688 .- 1469-4409. ; 135:5, s. 854-856
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Journal article (peer-reviewed)abstract
- Two variants of Listeria monocytogenes were isolated from blood cultures from each of two patients with listeriosis. Each variant displayed a two-band difference in DNA profile from the other by pulsed-field gel electrophoresis. Although this difference in profile is insufficient to distinguish clearly between the variants, the possibility of co-infection with different strains of L. monocytogenes needs to be considered. We suggest that more than one colony should be selected for molecular typing to aid interpretation during investigation of the sources and routes of Listeria infection.
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