Use of Pulsed-Field Gel Electrophoresis To Characterize the Heterogeneity and Clonality ofSalmonellaIsolates Obtained from the Carcasses and Feces of Swine at Slaughter

Abstract

Salmonella enterica isolates were recovered from swine at a collaborating processing plant over a 2-month period in the spring of 2000. In the present study, molecular subtyping by pulsed-field gel electrophoresis (PFGE) was performed on the 581 confirmed Salmonella isolates from the 84 Salmonella-positive samples obtained from the previous study. A total of 32 different PFGE pulsotypes were observed visually, and a BioNumerics software analysis clustered those pulsotypes into 12 PFGE groups. The B, F, and G groups predominated throughout the sampling period and were isolated from 39, 22, and 13% of the swine, respectively. In addition, multiple isolates were obtained from 67 of the 84 Salmonella-positive samples, and subtyping revealed multiple PFGE profiles in 35 of these 67 (62%) samples. Both carcass and fecal isolates of Salmonella were recovered from 13 swine, resulting in "matched" samples. Molecular typing of the 252 isolates recovered from the matched samples revealed that 7 (54%) of the 13 carcasses were contaminated with Salmonella pulsotypes that were not isolated from the feces of the same animal. Conversely, from 6 of the 13 (46%) matched animals, Salmonella clonal types were isolated from the feces that were not isolated from the carcass of the same animal. These data establish that each lot of swine introduces new contaminants into the plant environment and that swine feces from one animal can contaminate many carcasses. In addition, these results indicate that the examination of multiple Salmonella isolates from positive samples is necessary to determine the variety of potential contaminants of swine carcasses during slaughter and processing.

Use of Pulsed-Field Gel Electrophoresis of Conserved XbaI Fragments for Identification of Swine Salmonella Serotypes

“…enterica serovar (Copenhagen) DT104 has been extensively studied with XbaI restriction (5,7,10,14,17). The published subtypes for DT104 were or nearly were identical to the patterns found in our database.…”

“…It was found that the same bands mentioned above were conserved. Wonderling et al (17) used the same analysis program and parameters as those of this study. Their results showed grouping of serotypes by their XbaI PFGE subtypes with cluster analysis.…”

Genotyping, Phage Typing, and Antimicrobial Resistance of Salmonella Typhimurium Isolated from Pigs, Cattle, and Humans

“…A low frequency (2.7%) of ST isolates resistant to ciprofloxacin was reported in Taiwan from 1996 to 2001 (Hsueh et al, 2004), whereas our study and other previous studies identified no ST isolates that were resistant to ciprofloxacin (Gorman and Adley, 2004;Gross et al, 1998). Salmonella isolates from cattle and turkey are more often multi-drug resistant (MDR) than isolates from other species (Wonderling et al, 2003). The rate of MDR against >2 antimicrobial agents was 100% in cattle, 77.3% in pigs and 47.6% in humans.…”

“…Data analysis PFGE analysis was conducted according to the methods of Tenover et al (1995) and Wonderling et al (2003), with some modifications. Macro-restriction patterns were analyzed with BioNumerics software (Applied-Maths, Sin-Martens-Latem, Belgium) and banding patterns were compared using Dice coefficients with a 1% band position tolerance.…”

Evaluation of Pulsed-Field Gel Electrophoresis Profiles for Identification of Salmonella Serotypes

“…The bacterial isolates were fingerprinted by the XbaI-PFGE method, using the PulseNet protocol developed by the CDC (22). The gel images were processed and analyzed by BioNumerics software.…”