Antimicrobial Susceptibility Of Salmonella Enterica Subsp. Enterica Serovar Choleraesuis Strains From Wild Boar (Sus Scrofa) In Italy

An unusual mortality in wild boars (Sus scrofa Linnaeus, 1758) was observed in the Friuli Venezia Giulia region in north-eastern Italy, in 2013. Mortality was due to septicaemia caused by Salmonella enterica serovar Choleraesuis (Salmonella Choleraesuis), a swine-adapted serovar that may also lead to systemic infections in humans. In a public health perspective, wildlife can play a role at the Salmonella-animal-human-interface, since wild populations could act as a reservoir of this pathogen. Concerning S. Choleraesuis, some strains of this serovar, which may also be transmitted to humans by means of food, show resistance to different antibiotics with possible implications for human health, but currently, knowledge is still lacking. This study was aimed at assessing susceptibility to antimicrobials in the S. Choleraesuis isolates in wild boar from the cited outbreak (n=30), in order to gain more knowledge about the presence and distribution of antibiotic-resistant pathogens in wildlife of North-Eastern Italy. Tests used were disk diffusion (DD) and minimum inhibitory concentration (broth microdilution method, MIC). Moreover, an extended-spectrum beta-lactamases (ESBL) test was performed to identify ESBL-producing Enterobacteriaceae. Results indicated no resistance to beta-lactam antibiotics, while all isolates (100%) were resistant to spiramycin and tilmicosin by DD test, and 22/ 30 (73%) showed resistance to streptomycin by MIC. Since S. Choleraesuis may represent an emerging health problem for livestock and humans, due to both its pathogenicity and specific antibiotic-resistance, monitoring in sympatric swine and wild boars would be desirable.