A PCR-based strategy for simple and rapid identification of rough presumptive Salmonella isolates

The purpose of the present study was to investigate the application of ready-to-go Salmonella PCR tests, based on dry chemistry, for final identification of rough presumptive Salmonella isolates. The results were compared with two different biotyping methods performed at two different laboratories. The sensitivity of the BAX Salmonella PCR test was assessed by testing a total of 80 Salmonella isolates, covering most serogroups, which correctly identified all the Salmonella strains by resulting in one 800-bp band in the sample tubes.

The specificity of the PCR was assessed using 20 non-Salmonella strains, which did not result in any DNA band. A total of 32 out of the 36 rough presumptive isolates were positive in the PCR. All but one isolate were also identified as Salmonella by the two biochemical methods. All 80 Salmonella strains were also tested in the two multiplex serogroup tests based on PCR beads.

All strains belonging to the serogroups B, C-1, C-2-C-3, and D were grouped correctly. Among the 32 rough presumptive isolates identified, 19 isolates resulted in a band of 882 bp (serogroup B), 11 isolates resulted in a band of 471 bp (serogroup C-1), and two isolates showed a band of 720 bp (serogroup D).

In conclusion, rough presumptive Salmonella isolates can be conveniently confirmed to the serogroup-revel, using the pre-mixed PCR tests. The system can be easily implemented in accredited laboratories with limited experience in molecular biology.