Evaluation of Molecular Methods for Identification of Salmonella Serovars

Abstract

bClassification by serotyping is the essential first step in the characterization of Salmonella isolates and is important for surveillance, source tracking, and outbreak detection. To improve detection and reduce the burden of salmonellosis, several rapid and high-throughput molecular Salmonella serotyping methods have been developed.The aim of this study was to compare three commercial kits, Salm SeroGen (Salm Sero-Genotyping AS-1 kit), Check&Trace (Check-Points), and xMAP (xMAP Salmonella serotyping assay), to the Salmonella genoserotyping array (SGSA) developed by our laboratory. They were assessed using a panel of 321 isolates that represent commonly reported serovars from human and nonhuman sources globally. The four methods correctly identified 73.8% to 94.7% of the isolates tested. The methods correctly identified 85% and 98% of the clinically important Salmonella serovars Enteritidis and Typhimurium, respectively. The methods correctly identified 75% to 100% of the nontyphoidal, broad host range Salmonella serovars, including Heidelberg, Hadar, Infantis, Kentucky, Montevideo, Newport, and Virchow. The sensitivity and specificity of Salmonella serovars Typhimurium and Enteritidis ranged from 85% to 100% and 99% to 100%, respectively.It is anticipated that whole-genome sequencing will replace serotyping in public health laboratories in the future. However, at present, it is approximately three times more expensive than molecular methods. Until consistent standards and methodologies are deployed for whole-genome sequencing, data analysis and interlaboratory comparability remain a challenge. The use of molecular serotyping will provide a valuable high-throughput alternative to traditional serotyping. This comprehensive analysis provides a detailed comparison of commercial kits available for the molecular serotyping of Salmonella.

Assessment and Comparison of Molecular Subtyping and Characterization Methods for Salmonella

“…With the advent of whole-genome sequencing (WGS), in silico direct serovar determination has become the most used approach, and at least two Salmonella serovar databases and programs have been routinely used for in silico serotyping of Salmonella : SeqSero (Zhang et al, 2015) and SISTR (Yoshida et al, 2016a). SeqSero uses a database of 473 alleles representing 56 fliC antigenic types and 190 alleles representing 18 fljB antigenic types in a combined H-antigen database (Zhang et al, 2015).…”

Development of a real-time PCR method for the genoserotyping of Salmonella Paratyphi B variant Java

“…Other genoserotyping methods are based on molecular markers specific for some serotypes which are detected by PCR-based technologies (Franklin et al 2011 ; Maurischat et al 2015 ; Rajtak et al 2011 ; Yoshida et al 2016 ). For example, Malorny et al ( 2003 ) developed a PCR method for the differentiation between dT− and dT+ Salmonella strains as an alternative to the biochemical tests mentioned above.…”

Comparison of xMAP Salmonella Serotyping Assay With Traditional Serotyping and Discordance Resolution by Whole Genome Sequencing

“…Based on the manufacturer's information sheet, 74 serovars can be fully typed while 26 can be partially typed by O or H antigens. Although SSA has been tested in a number of studies from other countries (Dunbar and Jacobson, 2007 ; Dunbar et al, 2015 ; Liang et al, 2016 ; Yoshida C. et al, 2016 ; Zheng et al, 2017 ), the discrepancies were not well resolved by other molecular methods in previous studies. In this study, we employed WGS and SISTR to resolve the discrepancies between SAT and SSA (Yoshida C. E. et al, 2016 ).…”

“…Traditional serotyping is based on the reactions of between antibodies and cell-surface antigens (Laing et al, 2011 ). Genoserotyping assay does not necessary relate with phenotypic assay for genes may not be expressed (Yoshida C. et al, 2016 ). Therefore, it is reasonable that WGS was more consistent with xMAP than serotyping.…”