Phage-Based Typing Scheme for Salmonella enterica Serovar Heidelberg, a Causative Agent of Food Poisonings in Canada

Abstract

Salmonella enterica serovar Heidelberg is perhaps the second most frequent Salmonella serovar isolated from humans and the most common isolated from animals in Canada. This pathogen has shown increasing resistance to antimicrobial agents and mimics the multidrug resistance observed in S. enterica serovar Typhimurium strain DT 104. However, unlike for serovar Typhimurium, a rapid and inexpensive subtyping method has not been available for large-scale surveillance efforts. We developed a phage typing scheme and subtyped 2,523 strains of serovar Heidelberg from outbreaks, sporadic infections, and environmental sources in Canada between January 1991 and December 2000. All strains were sensitive to one or more phages and could be subdivided into 49 phage types. A total of 196 isolates from 13 major outbreaks could be subtyped into six phage types, while 86 strains from family outbreaks were assigned to seven phage types. All strains were typeable, and epidemiologically related strains isolated from patients and implicated foods had identical phage types, antibiograms, and pulsed-field gel electrophoresis (PFGE) patterns. Combining PFGE with phage typing increased the discriminatory power of the analysis beyond that of either method alone. We concluded that this phage typing scheme, in conjunction with PFGE, enhances subtyping of serovar Heidelberg strains. Furthermore, this phage typing scheme is a rapid, economical, stable, and reliable epidemiologic tool for tracing the origin of food-borne disease and for the surveillance of sporadic infections.

Salmonella isolates’ serotypes and susceptibility to commonly used drugs at a tertiary care hospital in Riyadh, Saudi Arabia

“…High prevalence of nontyphoidal Salmonellae has also been reported from other parts of the world [22][23][24], indicating that infections with non-typhoidal Salmonellae are a global problem. Infections due to multidrug resistant S. enterica serotype Typhi have also been regarded as major problems in several parts of the world [25].…”

“…Outbreaks of strains of S. enterica serotype Typhi resistant to all first-line drugs have been reported from the Indian subcontinent, Mexico, South Africa, and the Arabian Gulf [7,8,10,[20][21][22]. Similarly, nontyphoidal Salmonella strains resistant to the conventional first-line drugs have also been reported [14].…”

Comparison of Multilocus Sequence Typing, Pulsed-Field Gel Electrophoresis, and Antimicrobial Susceptibility Typing for Characterization of Salmonella enterica Serotype Newport Isolates

“…Numerous reports have documented the highly discriminatory nature of PFGE in successfully tracking infections of different Salmonella serotypes to certain geographic areas, including particular farms, and have subsequently linked human illness to exposure to animals or contaminated foods (4,16,17,28,36,42,48,49). However, a more discriminating method may be required to understand the evolutionary relatedness of epidemiologically unrelated populations (9,11,24,29,43,46).…”

DNA Sequence-Based Subtyping and Evolutionary Analysis of Selected Salmonella enterica Serotypes

“…Overall, our data indicate that both a seven-gene MLST and a three-gene sequence-typing scheme allow limited within-serotype discrimination for salmonellae; both schemes allowed for discrimination of only eight STs among our initial set of 25 Salmonella enterica isolates representing five serotypes. Sensitive subtyping of salmonellae with high within-serotype discriminatory ability has been documented for a variety of other subtyping techniques, such as MLEE, phage typing, and PFGE (1,8,33), indicating that these methods may provide for more-sensitive subtype discrimination for Salmonella enterica. In addition to a low level of discriminatory power, Salmonella MLST schemes also face the challenge of designing appropriate primers that allow for PCR amplification and sequencing of isolates representing at least the majority of common serotypes.…”

“…More-discriminatory methods for subtyping of Salmonella isolates include phage typing (8) as well as pulsed-field gel electrophoresis (PFGE) (1). Multilocus enzyme electrophoresis (MLEE) has also been used successfully to subtype Salmonella isolates and to study the evolution and population genetics of various Salmonella serotypes (2,28,31,32).…”