engleski

Molecular Epidemiology of Salmonella Infantis in Central Europe

In the last two decades, Salmonella Infantis became endemic in Hungarian poultry flocks leading to increased occurrence in humans. The dissemination of this serovar was associated with the emergence of the PFGE cluster B, characterized by the Nal-Sul-Tet phenotype, and the large multiresistance (MDR) prototype plasmid pSI54/04. Previously we found that plasmidic strains of the Hungarian MDR cluster B are also widespread in Europe and remained prevalent until recently in Hungary. Here, we aim to give a comparative overview of the distribution and molecular attributes of recent poultry strains of S. Infantis in Central European countries relative to our earlier reports from some of these and of other European countries including Hungary. For this purpose a total of116 strains of S. Infantis were tested, originating mostly from broilers (n:87), but strains from human clinical samples (n:25) and layers (n:4) were included for comparison. Strains were isolated between 2010-2016in Bulgaria, Czech Republic, Croatia, Germany, Poland, Romania and Slovenia. The antimicrobial resistance phenotype was determined for all strains of S. Infantis, based on which 40 strains -representing different AMR patterns were subjected for PFGE analysis and for resistance genotyping by our PCR microarray system. The co-existence of certain genes for antimicrobial resistance (tetA-merA-intI1-aadA1-sul1-tehA) and for virulence (irp1-fyuA-htrE-faeI-pefC) were used for the PCR-based detection of the prototype plasmid pSI54/04 and its variants. A 69.8 % of all the strains proved to be resistant to at least three different antimicrobials. The MDR phenotypes of Nal-Sul- Tet and Nal-Sul-Tet-Tmp were predominant (63.2% of the broiler and 48.6% of the human strains). Most of the strains with the above resistance patterns belonged to the PFGE cluster B. and 21.5% of the strains showed resistance to Nal only, or were pansensitive. Interestingly, 80.1% of the broiler strains from Croatia, and some human strains from Czech Republic represented these patterns. Carriage of the large MDR prototype plasmid pSI54/04 was typically detected in broiler strains showing the resistance patterns Nal-Su- Tet/-Tmp and belonging to the PFGE cluster B. Results on resistance genotyping showed the association between the pSI54/04 and blaTEM-1 plasmids in strains with co-resistance to ampicillin. In conclusion, resistance phenotyping and molecular analysis has shown the stabilization and constant circulation of the former major MDR cluster B of S. Infantis and its characteristic plasmid pSI54/04 not only in Hungarian poultry flocks but also in Central Europe with indications of further evolution of pSI45/04 and its associations with other plasmids mediating resistance to drugs with clinical significance.

molecular epidemiology, Salmonella infantis, poultry, human, antimicrobial resistance

Rad je prezentiran i na znanstvenom skupu: 26th Semmelweis Symposium - New Challenges in Microbiology, 9-10 November, 2017 Budapest, Hungary