P-030. Different Clones of Salmonella 4,5,12:I:- Isolates in Different Continents Causing Outbreaks

Y. Soyer1, A. Moreno2, M. A. Davis3, J. Maurer4, P. L. McDonough1, L. D. Warnick1, Y. T. Grohn1, M. Wiedmann1;
1Cornell Univ., Ithaca, NY, 2Univ. de Concepcion, Concepcion, CHILE, 3Washington State Univ., Pullman, WA, 4Univ. of Georgia, Athens, GA.

Background. Salmonellosis is a major cause of bacterial enteric illness in both animals and humans. Salmonella 4,5,12:I:- is closely related to Typhimurium but lacks the expression of second phase flagellar antigen. This serotype was the 6th most common Salmonella serotype among human cases in the US in 2005 and the 4th most common serotype among human isolates in Spain in 1998. Overall, the prevalence of Salmonella 4,5,12,I:- has increased considerably in many countries in the world over the last 10 years. Methods: We characterized 80 Salmonella 4,5,12:I:- and 72 Salmonella Typhimurium isolates from various sources such as human, bovine, food, avian, and canine from different states in the US (Georgia, New York and Washington) as well as 13 Salmonella 4,5,12:I:- and 30 Salmonella Typhimurium isolates from Spain. All isolates were characterized using a 4-gene multilocus sequence typing (MLST) scheme and XbaI pulsed field gel electrophoresis (PFGE) using the PulseNet protocol. Representative isolates were also screened, using PCR, for the presence of six genes (i.e., STM2740, STM2757, fljA, fljB, hin, iroB) and a specific region (upstream of hin)¸which is present in the whole genome of the 4,5,12:I:- strain CVM23701, but absent in S. Typhimurium LT2. Results: The 195 serotype 4,5,12:I:- and Typhimurium isolates characterized were differentiated into 9 MLSTs and 88 PFGE types. While the majority of 4,5,12:I:- and Typhimurium isolates 89 and 86 isolates, respectively), represented a single MLST type, all 4,5,12:I:- lacked fljA and fljB, which were present in all Typhimurium isolates. PCR screens further showed that all isolates from Spain carried the same deletion surrounding fljAB. This “Spanish” deletion genotype was found only once among US isolates, which typically carried a different deletion. PFGE patterns of the Spanish and US 4,5,12:I:- isolates also formed different cluster. Conclusion: Salmonella 4,5,12:I:- appears to represent two different emergence events, both from a serotype Typhimurium ancestor. These two 4,5,12:I:- clones differ in their geographical distribution, with different clones predominant in Spain and the US.