Outbreaks and sporadic cases of Salmonella serovar Panama studied by DNA fingerprinting and antimicrobial resistance

In the Principality of Asturias (PA), Spain, three Salmonella serovar Panama outbreaks were registered in August 1998. In order to achieve an accurate identification of the strains implicated in the outbreaks and to study the molecular epidemiology of this serovar in the PA, the isolates collected over 1990–1999 were examined by DNA fingerprinting and antimicrobial resistance analysis. The origin of the isolates was: human (65, of which 20 were associated with the three outbreaks), octopus (2), beef (2), eggs (7), poultry faeces (2), sea water (5), sewage (2) and unknown (1). Sixteen lineages were defined by ribotyping, enterobacterial repetitive intergenic consensus sequences analysis, and randomly amplified polymorphic DNA segment analysis. One lineage was endemic in the PA and was also represented by isolates from other Spanish regions. The organisms of this lineage can be differentiated (by resistance-, plasmid- and integron-profiles) into 19 types. The three outbreaks were caused by organisms falling into a single type (nalidixic acid-resistant, plasmid- and integron-free) belonging to the endemic lineage, which was associated with poultry as the reservoir. Isolates showing drug-resistance (71%) fell into six lineages and 23 types. Ten multidrug-resistant types carried class 1 integrons with three types of variable regions containing resistance gene cassettes.