Determination of plasmids in Salmonella enteritidis isolates (phage types 4 and 8) and their relationship with antimicrobial resistance

Abstract

Salmonellosis caused by Salmonella enteritidis (SE), is a zoonosis affecting birds and mammals, humans included. The purpose of this study was correlating the presence of plasmids with antimicrobial resistance in SE strains of poultry origin. Fifty (50) SE isolates were analyzed, including 21 phage type-4, and 29 phage type-8 isolates. The antimicrobial resistance test was performed using a commercial, Kirby-Bauer',s plate diffusion kit. Plasmids were extracted using the alkaline lysis method. Strains featuring 1 to 5 plasmids showed 100 % resistance to amikacin, gentamicin, netilmycin, and nitrofurantoin. Therefore it was not possible to correlate the resistance found in some strains with the presence of plasmids. All isolates shared a common 12 Kpb plasmid. All phage-4 isolates showed the presence of both 9 and 23 Kpb plasmids. These two plasmids were also found in phage-8 isolates, but they also showed two additional plasmids (3 and 6 Kpb',s), thus allowing for the differentiation between these two phage types.