Plasmid profile and pulsed-field gel electrophoresis analysis of Salmonella enterica isolates from humans in Turkey

Abstract

This study was conducted for typing Salmonella enterica subspecies enterica strains in Turkey using pulsed-field gel electrophoresis (PFGE) and plasmid DNA profile analysis. Fourty-two strains were isolated from clinical samples obtained from unrelated patients with acute diarrhea. The samples were collected from state hospitals and public health laboratories located at seven provinces in different regions of Turkey at different times between 2004 and 2010. The strains were determined to belong to 4 different serovars. The Salmonella enterica strains belonged to the serovars Salmonella Enteritidis (n = 23), Salmonella Infantis (n = 14), Salmonella Munchen (n = 2), and Salmonella Typhi (n = 3). Forty-two Salmonella enterica strains were typed with PFGE methods using XbaI restriction enzyme and plasmid analysis. At the end of typing, 11 different PFGE band profiles were obtained. Four different PFGE profiles (type 1, 4, 9, and 10) were found among serotype S. Enteritidis species, 3 different PFGE profiles (type 3, 5, 6) were found among S. Infantis species, 2 different PFGE profiles were found among S. Typhi species (type 2 and 11), and 2 different PFGE profiles were found among S. Munchen species (type 7, 8). The UPGMA dendrogram was built on the PFGE profiles. In this study, it was determined that 4 strains of 42 Salmonella enterica strains possess no plasmid, while the isolates have 1-3 plasmids ranging from 5.0 to 150 kb and making 12 different plasmid profiles (P1-P12). In this study, we have applied the analysis of the PFGE patterns and used bioinformatics methods to identify both inter and intra serotype relationships of 4 frequently encountered serotypes for the first time in Turkey.

Figure 1. Dendogram of S. enterica serovar isolates showing percent similarity has been calculated by the Dice similarity of PFGE (XbaI) restriction endonuclease digestion, constructed using UPGMA algorithm (Bionumerics version 6.01 software) by using 1.5% band tolerance and 1% optimization settings.

Figure 2. Examples of representative PFGE fingerprinting patterns of S. enteritidis, S. typhi, and S. infantis strains after restriction with SpeI enzymes.st31, st23, st4, st39, st35, st25, st27; M: PFGE marker (Supercoiled DNA, USA).