Evaluation of phenotypic and genotypic markers for characterisation of the emerging gastroenteritis pathogen Salmonella hadar.

Over the last 4 years Salmonella hadar has increasingly been isolated in Europe in conjunction with food-borne gastroenteritis. The aim of this study was to evaluate epidemiological methods (phage typing, antimicrobial susceptibility testing, DNA plasmid analysis, ribotyping and pulsed-field gel electrophoresis analysis) for characterising Salmonella hadar isolates. The 100% phage typeability of isolates and the high discriminatory index of 0.8856 suggest that phage typing is the method of choice. In order to obtain subdivisions of the most frequent Salmonella hadar phage types, a combination of molecular methods, such as ribotyping performed with Bg/I and EcoRI or pulsed-field gel electrophoresis using XbaI and XhoI, would be desirable as the usefulness of each technique varies with the phage type being analysed. Of note was the high (86%) rate of resistance to tetracycline and nalidixic acid but full susceptibility to ciprofloxacin in the strains studied.