The strength of the association between pCMY-2 and chromosomal genotype was confirmed (p =

0.001, OR = 93), since all the isolates harbouring pCMY-2 were ST213 (Table 3 and Additional file2). Distribution, genetic diversity and associations of pSTV The presence of pSTV was first assessed by PCR amplification of spvC. Only 30% of the isolates were positive for spvC [see Additional file2]. To confirm the presence or absence of the pSTV we amplified rck and traT for all 33 spvC positive isolates, and for 19 spvC negative isolates. All spvC positive isolates amplified traT and rck, with the exception of two isolates that did not amplify rck (slhs02–20 and slres03–40; see

AP24534 ic50 Additional file2); while the spvC negative isolates AZD5363 clinical trial did not produce amplifications with either rck or traT. To evaluate the genetic diversity of pSTV we determined the nucleotide sequences of spvC for 16 representative isolates [see Additional file2]. All spvC sequences (513 bp) were identical to each other, displaying only one nucleotide substitution with respect to the sequence of strain LT2 [GenBank:AE006471] [46]. We further determined the sequences of traT and rck for 11 and 9 isolates, respectively. The traT (450 bp) and rck (429 bp) sequences were also identical to each other and to the sequence of strain LT2. These results Terminal deoxynucleotidyl transferase show pSTV with a low level of genetic diversity distributed in the four geographic regions and recovered during the five sampled years. We confirmed the presence of pSTV and determined its approximate size by Southern blot hybridization

of plasmid profiles for 10 isolates. All the isolates that where positive for the amplification of spvC, rck and traT hybridized with a plasmid of the same size of that of the pSTV of strain LT2 (about 94 kb) [46], and all the negative controls produced no signal with the spvC probe. However, one of the isolates that did not amplify rck hybridized with a larger plasmid of about 120 kb, indicating that this pSTV is different, probably due to the insertion of mobile elements, such as transposons, as previously reported [19, 47]. pSTV was present in 29 ST19 isolates (68%), the four ST302 isolates (100%) and only one ST213 isolate (1%; yuhs03–80; Figure 4 and Additional file2). This finding indicates that pSTV was not randomly distributed among isolates, since 60% of the isolates were ST213, and showed a significant association between ST19, and pSTV (p = 0.001, OR = 144). Human isolates harboured pSTV significantly more than food-animal isolates (43% vs. 16%, p = 0.002, OR = 4.1), demonstrating a significant association with the human host.