Diversity of Salmonella strains isolated from the aquatic environment as determined by serotyping and amplification of the ribosomal DNA spacer regions

Salmonella species are pathogenic bacteria often detected in sewage, freshw ater, marine coastal water, and groundwater. Salmonella spp, can survive fo r long periods in natural waters, and the persistence of specific and epide mic strains is of great concern in public health. However, the diversity of species found in the natural environment remains unknown. The aim of this study was to investigate the diversity of Salmonella strains isolated from different natural aquatic systems within a Mediterranean coastal watershed (river, wastewater, and marine coastal areas). A total of 574 strains isola ted from these natural environments were identified by both conventional se rotyping and the ribosomal spacer-heteroduplex polymorphism (RS-HP) method (M. A. Jensen and N, Straus, PCR Methods Appl. 3:186-194, 1993). More than 10 different serotypes were found, and some serotypes probably mobilized fr om widespread animal-rearing activities were detected only during storm eve nts. These serotypes mag be good indicators of specific contamination sourc es. Furthermore? the RS-HP method based on the PCR amplification of the int ergenic spacer region between the 16S and 23S rRNA genes can produce amplic on profiles allowing the discrimination of species at both serotype and int raserotype levels. This method represents a powerful tool that could be use d for rapid typing of Salmonella isolates.