Performance of Techniques for Identification of Serotypes of Salmonella

Introduction: Traditional identification of the Salmonella genus has been routinely done by means of biochemical and serological characteristics. However, in recent years, several countries have focused requirements for poultry products in the control of some specific types of Salmonella, such as S. Enteritidis and S. Typhimurium. In this case, the product in which the presence of Salmonella is detected, the bacteria must be identified in some way to prove the presence or not of these serotypes.

Purpose: The purpose of this study was to compare different techniques for the identification and differentiation of Salmonella spp.

Methods: Thirty-five isolates of Salmonella obtained from chicken products were submitted to identification by classical serological, automated biochemistry VITEK 2 system (bioMérieux), mass spectrometry - MALDI-TOF Bio Typer (Bruker Daltonik), and by genetic analysis by ribotyping with microbial characterization RiboPrint® system (DuPont Qualicon).

Results: The serological technique identified the following serotypes: two S. Saintpaul, one S. Muenchen, two S. Mbandaka, two S. Newport, two S. Infantis, two S. Senftenberg and 24 S. Enteritidis.  All 24 isolates identified as S. Enteritidis by serological technique were also confirmed by the system.  Two isolates of S. Saintpaul and one of S. Senftenberg obtained in the serological technique were identified in the system as S. Typhimurium.  The other isolates were identified only on species level.  Using mass spectrometry all isolates were identified only as Salmonella spp.  The 15 isolates tested by RiboPrint^® were S. Enteritidis and the system confirmed the results.

Significance: The results obtained suggest that the system is reliable to identified S. Enteritidis, but limited for the others serotypes tested.  The RiboPrint^® showed high correlation with serological technique, although only isolates of S. Enteritidis were tested.  Mass spectrometry can be a promising technique for the identification of types of Salmonella but it requires further studies.