Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2003
Publication Date: 5/1/2004
Citation: Lopes, V.C., Velayundhan, B.T., Halvorson, D.A., Lauer, D.C., Gast, R.K., Nagaraja, K.V. 2004. Comparison Of Methods For Differentiation Of Salmonella Enterica Serovar Enteritidis Phage Type 4 Isolates. American Journal of Veterinary Research v.65 p.538-543 2004. Interpretive Summary: Salmonella enteritidis is an important food-borne pathogen for humans. In order to accurately identify the sources of S. enteritidis that contribute to disease outbreaks, it is important to have methods for differentiating strains of this organism based on their molecular genetic properties. The present study evaluated an assortment of molecular typing methods for their ability to distinguish between a set of 27 S. enteritidis phage type 4 strains isolated in the United States and Europe. Of the six methods tested, random amplification of polymorphic DNA (RAPD) provided the greatest degree of discrimination between the various S. enteritidis strains, allowing the grouping of similar strains into clusters. This demonstrates that the RAPD method can be a valuable tool for epidemiological investigations.
Technical Abstract: OBJECTIVE - To compare molecular typing methods for the discrimination of Salmonella enterica serovar Enteritidis (S. enteritidis) phage type (PT) 4 isolates, allowing for the determination of their genetic relatedness. SAMPLE POPULATION ' Twenty seven S. enteritidis PT 4 strains isolated in the United States and Europe were used in this study. PROCEDURE - Several molecular typing methods were performed to assess their ability to genetically discriminate S. enteritidis PT 4 isolates. The results of pulse-field gel electrophoresis (PFGE), Repetitive-Polymerase Chain Reaction (PCR), 16S rRNA gene sequencing, random amplification of polymorphic DNA (RAPD), PCR-restriction fragment length polymorphism of 16S rRNA and antimicrobial sensitivity were evaluated. RESULTS - Compared to other techniques evaluated in this study, RAPD typing method with RAPD1 primer revealed to be the most discriminatory fingerprinting technique, allowing for clustering of S. enteritidis PT 4 isolates by their genetic similarity. CONCLUSION AND CLINICAL RELEVANCE- This study demonstrates the value of RAPD with RAPD1 primer as a tool for epidemiological investigations of S. enteritidis PT 4. It can be used complementarily with PFGE and phage typing to determine genetic relatedness of S. enteritidis isolates involved in outbreaks. A reliable and highly discriminatory method for epidemiological investigations is critical in order to identify the source(s) of infections and, consequently, prevent the spread of outbreaks of S. enteritidis PT 4.