Evaluation and comparison of molecular techniques for epidemiological typing of Salmonella enterica subsp. enterica serovar dublin

Abstract

A total of 28 unrelated isolates of the Salmonella enterica subsp. enterica serovar dublin (S. dublin) collected during a 6-year period, as well as four samples of the S. dublin live vaccine strain Bovisaloral and its prototype strain S. dublin 442/039, were investigated by different molecular typing methods for the following reasons: (i) to find the most discriminatory method for the epidemiological typing of isolates belonging to this Salmonella serovar and (ii) to evaluate these methods for their capacity to discriminate among the live vaccine strain Bovisaloral, its prototype strain S. dublin 442/039, and field isolates of the serovar dublin. Five different plasmid profiles were observed; a virulence plasmid of 76 kbp as identified by hybridization with an spvB-spvC gene probe was present in all isolates. The detection of 16S rRNA genes and that of IS200 elements proved to be unsuitable for the epidemiological typing of S. dublin; only one hybridization pattern could be observed with each of these methods. The results obtained from macrorestriction analysis strongly depended on the choice of restriction enzyme. While the enzyme NotI yielded the lowest discriminatory index among all enzymes tested, it was the only enzyme that allowed discrimination between the Bovisaloral vaccine strain and its prototype strain. In contrast to the enzymes XbaI and SpeI, which only differentiated among the S. dublin field isolates, XhoI as well as AvrII also produced restriction fragment patterns of the Bovisaloral strain and of its prototype strain that were not shared by any of the S. dublin field isolates. Macrorestriction analysis proved to be the most discriminatory method not only for the epidemiological typing of S. dublin field isolates but also for the identification of the S. dublin live vaccine strain Bovisaloral.

Multiple-locus variable-number tandem repeat analysis ofSalmonella entericasubsp.entericaserovar Dublin

“…Dublin, there is no widely used phage type scheme, IS200restriction fragment length polymorphism profiles have been reported to be identical in most isolates, plasmid profiling is unsuitable as most isolates contain a single 52 MDa plasmid and pulsed-field gel electrophoresis (PFGE), which is widely used for Salmonella epidemiology, provides limited diversity within Salm. Dublin (Woodward et al 1989;Ferris et al 1992;Olsen and Skov 1994;Liebisch and Schwarz 1996). Therefore, there is a need for a molecular method that can provide a higher degree of polymorphism, so we can study the transmission routes of Salm.…”

Growth inhibitory factors in bovine faeces impairs detection of Salmonella Dublin by conventional culture procedure

“…The differences in growth and the observed differences in sensitivity demonstrate a dilemma in relation to diagnostics, as the sensitivity, and thus, the predictive value of a negative test result will depend on the strain that caused the infection. The genetic diversity among S. Dublin has been analysed by the use of epidemiological typing methods showing a high degree of clonality (Olsen and Skov 1994;Liebisch and Schwarz 1996;Liebana 2002), but to our knowledge, there is very limited information on the variation of in vitro growth properties within the natural population of S. Dublin.…”

Molecular characterization of Salmonella enterica subsp. enterica serovar Typhimurium DT009 isolates: differentiation of the live vaccine strain Zoosaloral from field isolates

“…enterica isolates of various serovars [11]. Thus, molecular typing systems which are based on plasmid analysis, ribotyping, IS200 typing and macrorestriction analysis have been established for a number of serovars, such as Typhimurium [1,2,12], Enteritidis [13^16], Dublin [8,17], Choleraesuis [9] or Hadar [18]. These typing systems enable the identi¢cation of single Salmonella isolates and their di¡erentiation from those of the same serovar and occasionally even from those of the same phage type [12^14,16].…”

“…These typing systems enable the identi¢cation of single Salmonella isolates and their di¡erentiation from those of the same serovar and occasionally even from those of the same phage type [12^14,16]. In the case of the Salmonella live vaccine strains Zoosaloral H [1,2], Bovisaloral [8] and Suisaloral [9], molecular typing provided means for an exact and reliable di¡erentiation of the vaccine strains from avian S. Typhimurium, bovine S. Dublin, and porcine S. Choleraesuis ¢eld isolates. In this study, we investigated whether, and if so which, molecular typing methods were suitable to distinguish between the S. Typhimurium live vaccine strain Zoosaloral and the most closely related S. Typhimurium ¢eld isolates, namely those of the same phage type.…”

“…The extraction of whole cell DNA for ribotyping and IS200 typing as well as restriction analyses of plasmid DNA and whole cellular DNA followed previously described protocols [1]. Speci¢c gene probes for the spvB/spvC virulence genes, 16S-23S-5S rRNA and the insertion element IS200, all labelled by the enhanced chemiluminescence system (ECL, Amersham-Buchler), were used in Southern blot hybridization experiments [1,8,9]. Whole cell DNA for pulsed-¢eld gel electrophoresis experiments was prepared as described [2] and digested with XbaI (Boehringer, Mannheim, Germany), SpeI (BioLabs, Bad Schwalbach, Germany), or BlnI (Amersham-Buch-ler).…”