Purpose: This study was conducted to identify and characterize Salmonella strains isolated the from peanut supply chain in Brazil.
Methods: Thirty-nine Salmonella strains isolated from different stages of the peanut supply chain were subtyped with pulsed-field gel electrophoresis (PFGE). These strains were evaluated for antimicrobial resistance (ampicillin, ceftazidime, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, cephaloxime, nalidixic acid, sulfonamide, streptomycin, trimethoprim, and tetracycline) using the disk diffusion assay. In addition, the presence of antimicrobial resistance genes (blatem, blapse, aadA1, floR and tet(G)) and virulence genes (invA, ipfA, avrA, and agfA)were investigated by PCR.
Results: Eight PFGE profiles were identified among six serotypes (Salmonella Muenster, Salmonella Miami, Salmonella Glostrup, Salmonella Javiana, Salmonella Oranienburg, Salmonella Yoruba) and were grouped into four clusters. Overall, a high resistance to sulfonamide (97.4%) was observed. Only one strain (2.5%) isolated from the postharvest step had resistance to sulfonamide and ampicillin. The strains had intermediary resistance to streptomycin (46.1%), kanamycin (33.3%), and ceftazidime (30.7%). The antimicrobial resistance genes related to ampicillin, cephaloxime, trimethoprim, chloramphenicol, and tetracycline were not detected in the analyzed strain. Virulence genes were found in isolates from different stages of the supply chain. InvA and agfA genes were detected in all 39 strains, whereas the avrA gene was detected in 12 strains and the ipfA in one strain.
Significance: The results suggested that the majority of the strains, isolated from the peanut supply chain in Brazil, are not multidrug resistant and carry relevant virulence factors into the Salmonella genus. Therefore, the study increases the knowledge of the epidemiology and molecular basis of antibiotic-resistance and virulence of Salmonella recovered in low water activity food.