Methodologies for Salmonella enterica subsp. enterica Subtyping: Gold Standards and Alternatives

Abstract

2For more than 80 years, subtyping of Salmonella enterica has been routinely performed by serotyping, a method in which surface antigens are identified based on agglutination reactions with specific antibodies. The serotyping scheme, which is continuously updated as new serovars are discovered, has generated over time a data set of the utmost significance, allowing long-term epidemiological surveillance of Salmonella in the food chain and in public health control. Conceptually, serotyping provides no information regarding the phyletic relationships inside the different Salmonella enterica subspecies. In epidemiological investigations, identification and tracking of salmonellosis outbreaks require the use of methods that can fingerprint the causative strains at a taxonomic level far more specific than the one achieved by serotyping. During the last 2 decades, alternative methods that could successfully identify the serovar of a given strain by probing its DNA have emerged, and molecular biology-based methods have been made available to address phylogeny and fingerprinting issues. At the same time, accredited diagnostics have become increasingly generalized, imposing stringent methodological requirements in terms of traceability and measurability. In these new contexts, the hand-crafted character of classical serotyping is being challenged, although it is widely accepted that classification into serovars should be maintained. This review summarizes and discusses modern typing methods, with a particular focus on those having potential as alternatives for classical serotyping or for subtyping Salmonella strains at a deeper level.

Genetic diversity of food originated Salmonella isolates

“…Numerous reports have been documented that using the highly discriminatory technique of PFGE was successful to track the source of Salmonella infections in different serovars [17][18][19][20][21]. However, PFGE does not display equal sensitivity in different serovars [14,21] and it has several limitations including changes in DNA concentration, percent of agarose in the gel, applied voltage and gel temperature. Beside these, it requires at least 3-4 days labour intensive to complete the test and the presence of expensive specialized equipment and high quality chemicals [7,22,23].…”

“…In addition to this, it has been used in typing Salmonella in human patients, animal sources and foods because of its discriminatory power and high reproducibility [14][15][16]. Numerous reports have been documented that using the highly discriminatory technique of PFGE was successful to track the source of Salmonella infections in different serovars [17][18][19][20][21]. However, PFGE does not display equal sensitivity in different serovars [14,21] and it has several limitations including changes in DNA concentration, percent of agarose in the gel, applied voltage and gel temperature.…”

Molecular Characterization of Antibiotic-Resistant Bacteria in Contaminated Chicken Meat Sold at Supermarkets in Bangkok, Thailand

“…The recently published review on new alternative methodologies for S. enterica subsp. enterica subtyping by Wattiau et al emphasizes the importance of DNA-based typing schemes (44). Furthermore, the latest MLST findings can demonstrate evolutional grouping better than serotyping, which sometimes can mislead an epidemiological investigation (45).…”

Salmonella Enteritidis predominance determined by serotyping andreal-time PCR in poultry-derived food and avian isolates

“…Differences in the detection rate of SE by rPCR in this study compared to the findings of others could mainly be related to the country and prevalence of the serovar in that region during that time period. In addition, sample size and type, and the validity of the PCR detection system (specificity, sensitivity, accuracy/reliability), can be the main factors among others affecting this outcome (7,8,30).…”