Molecular characterisation of emergent multiresistant Salmonella enterica serotype [4,5,12:i:-] organisms causing human salmonellosis

Salmonella multidrug-resistant clinical organisms identified as serotype 4,5,12:i:-] were typed using selected genetic procedures and compared with typhimurium organisms collected in the same Spanish region. Results showed a low genetic heterogeneity among 4,5,12:i:-] organisms, which generated identical ribotypes and similar but not identical XbaI PFGE, RAPD, and plasmid profiles. Multidrug resistance could be eliminated by curing and seems to be mediated by 140-kb (spvC+) and 120-kb (spvC-) non-self-transferable plasmids. The 4,5,12:i:-] organisms fall into a single genetic lineage, which emerged in 1997 and presents a different degree of genetic relationship with typhimurium lineages.