Analysis of the clonal relationship among clinical isolates of Salmonella enterica serovar Infantis by different typing methods.

Salmonella Infantis has been the second most common serovar in Argentina in the last two years, being isolated mostly from paediatric hospitalised patients. In order to determine the clonal relationship among Salmonella Infantis strains, we examined 15 isolates from paediatric patient faeces in Argentina (12 geographically related and 3 geographically non-related) by using antimicrobial susceptibility, plasmid profiling, repetitive extragenic palindromic (REP) PCR, enterobacterial repetitive intergenic consensus (ERIC) PCR, and low-frequency restriction analysis of chromosomal DNA by pulsed field gel electrophoresis (PFGE). Four Spanish strains were included as controls of clonal diversity in molecular techniques. Antibiotype and plasmid profile was not useful as epidemiological tools. PFGE and REP-PCR were able to discriminate between Argentinean and Spanish isolates of Salmonella Infantis allowing to detect genetically related strains in three different cities. This finding indicates that a possible spread of a clone of this serovar in the North-eastern Region of Argentina has taken place in 1998.