Potential of three-Way randomly amplified polymorphic DNA analysis as a typing method for twelve Salmonella serotypes

The potential of a three-way randomly amplified polymorphic DNA (RAPD) procedure (RAPD typing) for typing Salmonella enterica strains assigned to 12 serotypes was analyzed. The series of organisms used included 235 strains (326 isolates) collected mainly from clinical samples in the Principality of Asturias and 9 reference strains. RAPD typing was performed directly with broth cultures of bacteria by using three selected primers and optimized PCR conditions. The profiles obtained with the three primers were used to define RAPD types and to evaluate the procedure as a typing method at the species and serotype levels. The typeability was 100%; the reproducibility and in vitro stability could be considered good. The concordance of RAPD typing methods with serotyping methods was 100%, but some profiles obtained with two of the three primers were obtained with strains assigned to different serotypes. The discrimination index (DI) within the series of organisms was 0.94, and the DI within serotypes Typhimurium, Enteritidis, and Virchow were 0.72, 0.52, and 0.66, respectively. Within these serotypes the most common RAPD types were differentiated into phage types and vice versa; combining the types identified by the two procedures (RAPD typing and phage typing) resulted in further discrimination (DI, 0. 96, 0.74, and 0.87, respectively). The efficiency, rapidity, and flexibility of the RAPD typing method support the conclusion that it can be used as a tool for identifying Salmonella organisms and as a typing method that is complementary to serotyping and phage typing methods.