Development and evaluation of multilocus variable number tandem repeat analysis for fine typing and phylogenetic analysis of Salmonella enterica serovar Typhimurium

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

“…dMultiplex PCRs were performed using primers for the following VNTR loci: M1 (Sty20, Sty37, Sty39 and Sty40); M2 (Sty25, Sty41, Sty44 and Sty45); M3 (Sty2, Sty3 and Sty42). related isolates of some monomorphic bacteria for the investigation of disease outbreaks (Chiou et al, 2010;Noller et al, 2003;Torpdahl et al, 2007). A previous study (Liang et al, 2007) showed that MLVA, based on only four highly variable VNTR markers, exhibited a level of discrimination that was significantly higher than that provided by PFGE for the S. sonnei isolates analysed.…”

“…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).…”

Salmonella enterica Serovar Typhi Variants in Long-Term Carriers

“…PFGE has been adopted as the standard subtyping tool in the PulseNet food-borne disease surveillance network (7,8). The MLVA typing scheme based on rapidly evolving VNTR loci is more discriminatory than PFGE in discerning very closely related strains of S. Typhi and other bacterial organisms (3,5,6,9). However, both methods seem to be too discriminatory for S. Typhi in these 3 outbreaks; the use of PFGE and MLVA data alone would exclude the epidemiological association of the cases from the corresponding outbreak.…”

Antimicrobial susceptibility and MLVA analysis of S. Typhimurium strains isolated from human and poultry samples in Tunisia

“…The nomenclature of the loci is different in the MLVA protocols, but they are overlaping VNTR loci [24]. Moreover, it has been proved that the discrimination power obtained by a 4-loci or 5-loci MLVA scheme is realy close, and that adding more loci to the scheme does not increase the resolution power of the technique [25,33].…”

“…MLVA profiles were expressed as a string of five numbers (ST7-ST6-ST5-STTR10-ST8). For ST7, ST6, ST5 and STTR10 locus, each value represent the repeat copy number according to the nomenclature suggested by Larsson et al [10], and for ST8 locus, the value was designated by the size of repeat array region as suggested by Chiou et al [25]. To assign the copy number the value was rounded down to the nearest complete copy number [26].…”