Boel, Jeppe

Löfström, Charlotta

Sisic, Emina

Sørensen, Gitte

Thomsen, Maria E.

Salmonella is an important zoonotic pathogen and meat, including pork, is one of the main sources of salmonellosis. Surveillance of Salmonella in the meat production chain is therefore essential to increase food safety. To enable e.g. source attribution and to reveal the source of outbreaks methods for subtyping is necessary and serotyping is one of the most commonly used approaches for Salmonella. Traditionally, serotyping is done by slide agglutination using antisera aiming at two cell surface antigens: somatic (O) lipopolysaccharides (LPS) and flagellar (H). Some Salmonella strains have incomplete LPS structures, referred to as rough strains, or do not express H antigens, therefore serotyping by agglutination cannot be performed on these isolates. This results in data gaps when subtyping data is needed. To overcome this obstacle, serotypes can be determined on DNA level, i.e. by determining the presence of genes encoding the O and H antigens using molecular serotyping. The aim of this study was to use molecular serotyping on rough Salmonella strains isolated from pork production in Denmark and to assess if the serotypes obtained differed from serotypes found for strains isolated during the same time period from similar sources. A number of rough Salmonella strains (n = 211) isolated from pig carcasses during 2005-2012 were analyzed with molecular serotyping employing Luminex technology. Results show that molecular serotyping enabled serovar identification in 168 of the strains (80%). The most common serotypes were Typhimurium (n=92; 44% of the 211 strains), Derby (n=40; 19%), 4,(5),12:i:- (n=22; 10%), Infantis (n=8; 4%) and others (n=6; 3%). Results for strains (n = 1233) isolated during the same years from similar sources where typing using traditional serotyping was possible (smooth strains) showed a similar pattern in serotypes found, where Typhimurium (n=547; 44%), Derby (n=399; 32%) and 4,(5),12:i:- (n = 72; 6%) also were the most common serotypes. Studies are in progress to serotype the remaining 43 rough strains using other DNA based techniques to further assess the difference in results between molecular and traditional serotyping. In conclusion, our preliminary data suggests that molecular serotyping of rough Salmonella strains mirrored the serotypes obtained using traditional serotyping for smooth strains

Sisic, E.

Thomsen, M.

Online Research Database In Technology

Molecular serotyping of rough Salmonella strains isolated from Danish pork production

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 19, 2017Molecular serotyping of rough Salmonella strains isolated from Danish porkproductionLöfström, Charlotta; Boel, Jeppe; Sisic, Emina; Thomsen, Maria E.; Sørensen, GittePublication date:2013Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Löfström, C., Boel, J., Sisic, E., Thomsen, M. E., & Sørensen, G. (2013). Molecular serotyping of roughSalmonella strains isolated from Danish pork production. Poster session presented at 10th International Meetingon Microbial Epidemiological Markers, Paris, France.Molecular serotyping of rough Salmonella strains isolated from Danish pork production Aim • To assess the use of molecular serotyping on rough Salmonella strains isolated from pig carcasses in Denmark • To assess if the serotypes obtained by molecular serotyping differed from the serotypes found using traditional serotyping for strains isolated during the same time period from the same source.  Introduction Surveillance of Salmonella in the meat production chain is essential to increase food safety. Serotyping is one of the most commonly used approaches for subtyping Salmonella.  Rough strains of Salmonella autoagglutinate, and this impedes the use of traditional serotyping by agglutination. To overcome this, serotypes can be determined on DNA level, e.g. by using molecular serotyping.  In the present study we used a molecular approach based on the Kauffmann-White scheme to detect the presence of genes encoding the corresponding O and H antigens [1,2]. By using this approach it is possible to compare results with molecular serotyping to results obtained using traditional serotyping.  Materials and Methods A number of rough Salmonella strains (n = 211) isolated from Danish pig carcasses during 2005-2012 were analyzed with molecular serotyping employing Luminex technology (Fig. 1). The assay covers O groups B, C1, C2, D, E and O:13, and 33 H antigens [1, 2] . Data from traditional serotyping [3] performed on isolates from the same years (n = 1233) were used for comparison.   Charlotta Löfström, Jeppe Boel, Emina Sisic, Maria E. Thomsen, Gitte Sørensen  National Food Institute, Technical University of Denmark, Søborg Conclusion • Serotyping results for molecular serotyping of rough Salmonella strains mirrored the serotypes obtained using traditional serotyping for strains isolated from the same source during the same time period.  Results and Discussion Results show that molecular serotyping enabled serovar identification in 168 of the 211 rough strains (80%) (Fig. 2A & 2B.) Results for strains (n = 1233, Fig. 2A) isolated during the same years from the same source, for which typing using traditional serotyping was possible, showed a similar pattern as the rough strains analyzed using molecular serotyping (Fig. 2B).                  The lack of molecular serotyping results for the 43 strains had several reasons. The most common obstacle was technical issues, that we expect will be solved when re-analyzing the strains.   For about 1/3 of the 43 strains it was not possible to identify the serotype with molecular serotyping, because these types were not covered by the assay. This could be resolved by the inclusion of additional markers.  Studies are in progress to serotype the remaining 43 rough strains using other DNA based techniques (e.g. sequencing) to further assess the difference in results between molecular and traditional serotyping.          References 1. Fitzgerald et. al. 2007 JCM 45 (10): 3323-3334 2. McQuiston et al. 2011 JCM 49 (2): 565-573 3. Grimont, & Weill. 2007. Antigenic Formulae of the Salmonella Serovars, 9th Ed..  Acknowledgements  Gunhild Larsen is acknowledged for excellent technical assistance. Figure 2. Comparison of results obtained for traditional slide agglutination serotyping (diagram A) and molecular serotyping (diagram B). NT: Not typeable (traditional serotyping: rough strains; molecular serotyping: technical problems, or impossible to get complete O and H types). For each serotype the name, no. of strains and % of the total no. of strains are given. Salmonella isolate DNA extraction • Data analysis • Transformation into O and H antigen types • Based on this a serotype is obtained • Amplification of DNA • Hybridization • Detection  • Using Luminex technology in the BioPlex Instrument Figure 1. Overview of the molecular serotyping process. A. Traditional serotyping results  (n = 1233) B. Molecular serotyping results for the NT strains from traditional serotyping  (n = 211) London  n=15; 1% 9,12;l,v:- n=18; 1% Livingstone  n=26; 2% 4,[5],12:i:-  n=72; 5% Infantis n=76; 5% Other n=80; 5% NT n=211; 15% Derby n=399; 28% TyphimuriuPn=547; 38% London  n=1; 1% 4,[5],12:i:-  n=22; 10% Infantis n=8; 4% Other n=5; 2% NT n=43; 20% Derby n=40; 19% TyphimuriXPn=92; 44% 

http://orbit.dtu.dk/ws/files/59057863/L%C3%B6fstr%C3%B6m%20et%20al%20poster%20IMMEM%20-10%20final.pdf

Molecular serotyping of rough Salmonella strains isolated from Danish pork production

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology

Online Research Database In Technology