Characterization of MDR plasmids The prevalence

of plasmid profile determined by plasmid number and size differed between these two serovars. Most S. Braenderup GSK872 purchase isolates [93.3%, (42/45)] carried plasmids, while few S. Bareilly isolates [23.5 % (12/51)] did (Figure 1). Plasmids larger than ca.75 kb were only found in resistance isolates of cluster A with the R4 to R8 patterns. Cluster B S. Braenderup isolates and S. Bareilly isolates carried smaller plasmids with the size smaller than 6.6 kb or lacked plasmids. Larger plasmids were further identified as R plasmids by analysis of the antimicrobial resistance profiles of E. coli pir116 transformants, and assigned to type 1 and 2 based on HindIII-restriction patterns (Table 3, Figure 2). Further conjugation, antibiotic resistance and PCR characterization of incompatibility and oriT types, mobile element IS26, class 1 integron, and AMP resistance genes bla TEM and bla CMY-2 were GSK126 molecular weight this website performed for these two plasmid types. Type 1 plasmids were separated into 7 subtypes (1a ~1g) based on differences in plasmid size ranging from 99.1 kb to 137.4 kb and restriction pattern. All

plasmids carried bla TEM, replicons F1A and F1B, IS26, and a class 1 integron (Additional files 1 and 2: Figure S1 and S2) with a gene cluster of dfrA12-orfF-aadA2-qacEΔ1-sulI, conferring resistance to trimethoprim-sulfamethoxazole (Sxt) and disappearing in plasmid 1 g (Table 3), which apparently coincides with that in the plasmid of S. Typhimurium (Accession number AB365868). The size of R plasmid was associated with antimicrobial resistance and conjugation

capability (Table 3). Only type 1a plasmids, with a size of 137.4 kb and conferring resistance to AMP, CHL, KAN, Sxt and TET, and 1b plasmids, Tolmetin with a size of 122.6 kb and encoding resistance to AMP and Sxt, were capable of conjugation, with efficiencies ranging 4.22 ~ 8.25 × 10-6. The other smaller plasmids, with sizes ranging from 99.1 kb to 104.8 kb and encoding resistance to AMP and Sxt for 1c-1e and 1g, and to AMP, CHL, Sxt and TET for 1f, were not capable of conjugation. Due to differences in plasmid size and since IS26 could be involved in plasmid transposition and recombination, we performed PCR amplification with the IS26 in primers and IS26out primers for all type 1 plasmids (Figure 3). In contrast to a 1.1-kb PCR product in the largest 1a plasmid, 1b, 1d, and 1e plasmids lacked any PCR products; 1e and 1g plasmids presented 3.1 kb PCR products; and 1c plasmid yielded two PCR products with sizes of 3.1 kb and 0.7 kb. These results suggest that the number of IS26 and/or distance between two IS26 elements differed among these type 1 plasmids. In contrast to type 1 plasmids, type 2 plasmids were much smaller in size (77.5 kb and 85 kb) and had higher conjugation efficiencies, ranging from 8.41 × 10-2 to 1.28 × 10-1 (Table 3).