Comparison of Multiple-Locus Variable-Number Tandem Repeat Analysis, Pulsed-Field Gel Electrophoresis, and Phage Typing for Subtype Analysis of Salmonella enterica Serotype Enteritidis

Abstract

Strain subtyping is an important tool for detection of outbreaks caused by Salmonella enterica serotype Enteritidis. Current subtyping methods, however, yield less than optimal subtype discrimination. In this study, we describe the development and evaluation of a multiple-locus variable-number tandem repeat analysis (MLVA) method for subtyping Salmonella serotype Enteritidis. The discrimination ability and epidemiological concordance of MLVA were compared with those of pulsed-field gel electrophoresis (PFGE) and phage typing. MLVA provided greater discrimination among non-epidemiologically linked isolates than did PFGE or phage typing. Epidemiologic concordance was evaluated by typing 40 isolates from four food-borne disease outbreaks. MLVA, PFGE, and, to a lesser extent, phage typing exhibited consistent subtypes within an outbreak. MLVA was better able to differentiate isolates between the individual outbreaks than either PFGE or phage typing. The reproducibility of MLVA was evaluated by subtyping sequential isolates from an infected individual and by testing isolates following multiple passages and freeze-thaw cycles. PFGE and MLVA patterns were reproducible for isolates that were frozen and passaged multiple times. However, 2 of 12 sequential isolates obtained from an individual over the course of 36 days had an MLVA type that differed at one locus and one isolate had a different phage type. Overall, MLVA typing of Salmonella serotype Enteritidis had enhanced resolution, good reproducibility, and good epidemiological concordance. These results indicate that MLVA may be a useful tool for detection and investigation of outbreaks caused by Salmonella serotype Enteritidis.

Emergence and clonal dissemination of Salmonella enterica serovar Enteritidis causing salmonellosis in Mauritius

“…Given the limited discriminatory power of pulse-field gel electrophoresis (PFGE) to differentiate strains of Salmonella serovar Enteritidis, a more discriminatory molecular subtyping method (MLVA) was utilized [18]. Retrospective data analysis identified a marked increase beginning in 2008, in both human NTS serogroup O:9 infections and the recovery of NTS serogroup O:9 from raw chicken and ready to eat food products in Mauritius.…”

Molecular Epidemiology of Nontyphoidal Salmonella in Poultry and Poultry Products in India: Implications for Human Health

“…Isolates generated restriction fragments with molecular size ranging from 40 to 700 kb fragments, representing 11 distinct macro restriction profiles. Dendrogram showing similarities of Xba1 digested macro restriction profiles of NTS isolates generated by bio-rod finger printing with the band matching coefficient of Dice and the UPGMA clustering many laboratories [32][33][34]. Genotyping of Salmonella is a rapidly expanding field and many new methods have been developed in recent years.…”

Use of multilocus variable-number tandem repeat analysis in molecular subtyping of Salmonella enterica serovar Typhi isolates

“…It has been widely used as a subtyping tool for the investigation of disease outbreaks (Hyytiä-Trees et al, 2007) and it was also adopted as a standard subtyping tool for an international foodborne disease surveillance network . However, in some cases, PFGE is insufficient in distinguishing between epidemiologically unlinked isolates of genetically monomorphic pathogens, such as Shigella sonnei (Liang et al, 2007), Escherichia coli O157 : H7 (Noller et al, 2003), Salmonella enterica serovar Enteritidis (Boxrud et al, 2007) and Salmonella enterica serovar Typhimurium (Chiou et al, 2010;Torpdahl et al, 2007). On the other hand, PFGE is too discriminatory to be an appropriate typing tool for the investigation of the global spread of bacterial clones (Spratt, 2004).…”