Antimicrobial susceptibility of Salmonella spp. strains isolated from free-living birds

Salmonella is one of the most common causes of food poisoning in the European Union and the United States of America. Free-living birds are known as a reservoir for the different serovars of Salmonella, including S. Typhimurium, S. Enteritidis, S. Infantis, S. Newport and S. Hadar, which may play an important role in the epidemiology of salmonellosis in farm animals, particularly poultry. Also, the antibiotic resistance of Salmonella spp. is a growing, public health emergency. In the present study, the authors examined 36 Salmonella spp. strains, which belonged to 3 subspecies; enterica, salamae and houtenae. All of them were obtained from 13 species of free-living birds in Poland. The antimicrobial susceptibility of these Salmonella strains was determined, using commercial SensititreTM Salmonella, MIC plates, for fourteen antimicrobials, from nine antimicrobial groups: sulfonamides, aminoglycosides, fluorochinolones, cephalosporines, beta-lactams, tetracyclines, phenicols, polymyxins and trimethoprim. The prevalence of selected genes which determine antimicrobial resistance; i.e. aadB, aacC, blaTEM, blaPSE-1, blaOXA, tetA, tetB, tetC, tetG, cat1, cat2, cat3 and floR was also tested. Among all of the examined strains, no resistance was detected in relation to gentamicin, cefotaxime and ceftazidime, while most strains (94.5%) were resistant to sulfamethoxazol. Among the 36 examined bacteria isolates, twenty were resistant to more than one antimicrobial agent. The antimicrobial resistant gene, floR was most frequently detected among all examined strains (50%).