Comparison of epidemiological markers of Salmonella strains isolated from different sources in Spain

A comparative study of the phage types, antimicrobial susceptibility patterns, and plasmid profiles of 171 strains of Salmonella isolated from food, epidemic outbreaks, and water-contaminated environments as well as sporadic human isolates was carried out to determine the most adequate marker in epidemiological investigations. Typing based on the plasmid profiles appears to be the most effective method for grouping strains with the same serotype obtained from a single outbreak and from environmental sources. However, none of the three markers tested allow us total discrimination and identification of related strains from a common source for epidemiological tracing. Therefore, the combined use of the three methods is necessary for determining whether common source isolates are related.