Population structure of multidrug-resistant non-typhoidal Salmonella enterica isolates from Portugal

Abstract number: P1315

Antunes P., Mourão J., Freitas A.R., Peixe L.

Objectives: Salmonellosis is one of the most common foodborne infections in Europe and multidrug-resistant (MDR) Salmonella is emerging worldwide with increasing involvement of particular clones. Our aim was to analyze the population structure of MDR nontyphoidal Salmonella enterica isolates in order to assess the relationship between antibiotic resistance genetic elements and MLST genotypes.

Methods: We selected 40 Salmonella isolates from a large Portuguese collection (2002–2008), representative of MDR clones from human infections (n = 21), food (n = 14), environment (n = 1) and piggeries (n = 4). Clonal relatedness was established by PFGE and MLST ( Analysis of antibiotic resistance genetic elements included characterization of plasmid and integron backbones (PCR, sequencing), transferability and genomic location (I-CeuI/S1 nuclease hybridization).

Results: The isolates studied (13 serotypes) corresponded to 24 PFGE types and 16 different sequence types (STs) including a new combination of known alleles. Most S. Typhimurium (n = 16/18; 4 PFGE types) belonged to the worldwide spread ST19 (n = 14) and to its SLV, ST313 (n = 1). They included the 3 most widespread clones in Portugal (DT104, OXA-30/CMY-2 and sul3) carrying different integron types and Inc plasmids (FIIA, A/C, I1, N). The globally disseminated ST11 was identified in all but one of the S. Enteritidis isolates (n = 4; 2 PFGE-types), including one carrying qnrS and belonging to a major clone. Isolates belonging to the emerging S. Rissen clone (n = 5) were assigned to the singleton ST469 or to its SLV, a new ST, only previously reported in European isolates of the same serotype. The remaining MDR isolates of different serotypes were identified as ST15, ST27, ST32, ST40, ST82, ST334 and the singletons ST48, ST64, ST102, ST306 and ST358. Mostly, a ST represented a single serotype. Distribution of different plasmids (IncFIIA, IncP, IncI1, IncN) and integron types was observed among different clonal lineage. Particular integrons and plasmids (IncA/C, IncHI1) were confined to specific STs.

Conclusions: This is the first study describing the population structure of Salmonella in Portugal. Our results confirm the prevalence of particular clusters enclosing major MDR clones that cause human infections. The selection and worldwide spread of particular STs might be influenced by the acquisition and horizontal transfer of specific resistance genes and genetic elements.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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