The differences in conjugation frequencies among pA/C + pX1 and pX1::CMY transconjugants with those of pX1, led us to determine that the transposition and co-integration events occurred within YU39 at frequencies ranging between 10-6 and 10-9, which were in the range of those reported for other transposition or co-integration events [18, 43, 44]. These results indicated that the first round conjugation frequencies combined the low frequency of co-integration or transposition Selleckchem Roxadustat with the high frequency of conjugation of pX1 (Table 5); while the second round conjugations directly measured the conjugation frequencies of pA/C + pX1 or pX1::CMY, which were high in most of
the cases due to the use of the pX1 conjugative machinery
(Table 3 and Table 4). trans-mobilization of pColE1-like The mobilization capacities of ColE1 related plasmids have been recognized for decades, and plasmids from several incompatibility groups have been shown to mobilize them . ColE1-like plasmids are prevalent in Salmonella serovars , and most of them carry the Km resistance gene aph[47, 48]. The YU39 pColE1-like did not confer Km resistance nor to any other of the YU39 antibiotic resistances tested (data not shown). Despite the high frequency of transfer of the pColE1-like plasmids, our hybridization assays demonstrated that this plasmid was not involved in the genetic re-arrangements displayed by pA/C and pX1, or the acquisition of the bla CMY-2 gene. Taken together, these results suggest that pColE1-like is a JQ1 manufacturer very efficient molecular parasite. However, only the determination of its complete nucleotide sequence could provide information regarding the presence of a gene increasing the fitness of its host bacteria. Epidemiological implications Our study demonstrated that pSTV and pA/C can indeed co-exist within E. coli and Typhimurium strains. Therefore, our original epidemiological observations that each of these plasmids was restricted to distinct genotypes  cannot Resminostat be explained by negative interactions between them. In our previous studies
we showed that the only strain capable of conjugative transfer of bla CMY-2 was YU39 . We screened the Mexican population for the presence of pX1, but YU39 was the only positive strain (data not shown), explaining why the other ST213 pA/C lacked the capacity to be transferred. We hypothesize that pA/C emerged in ST213, which is a genotype lacking pSTV, and that the non-conjugative pA/C failed to colonize ST19 strains. The widespread dissemination of pA/C and bla CMY-2 in the ST213 population by the action of YU39 pX1 is a rare, but not negligible, event. Future epidemiological studies designed to track the prevalence of pX1 in the Mexican populations will shed light on these interactions.