Genetic_Diversity_no antibiotic

We investigated the genetic diversity of 900 randomly selected E. coli isolates obtained from 20 fecal samples derived from pigs belonging to five different age groups allocated Danish farm where pigs did not receive antimicrobials. The genetic diversity was assessed by using repetitive extragenic palindromic- PCR (REP-PCR), followed by pulsed field gel electrophoresis (PFGE). The genetic relationship between strains at the farm level, as well as within age group was also analyzed. A total of 52 unique REP profiles were detected. The dominant profiles, R1, R7 and R28 were the most frequently detected strains in this study are similar to our previous studies, suggesting these strains represent the archetypal E. coli circulating in Danish pigs. The level of diversity observed was higher compared to recent studies where nursery pigs were treated with different antimicrobials suggesting that absence of antimicrobial treatment could be a cause of diverse E. coli commensal population. Among the different age groups, the highest and the lowest diversity were found in the early weaner (H' of 2.215) and piglet (H' of 1.461) respectively. E. coli isolates yielding to unique REP profiles and several strains assigned to the most frequent profiles were subjected to PFGE and led to 67 different genotypes which were also compared. This is the first report on the genetic diversity of commensal E. coli from guts of pigs reared in an antibiotic free production system and belonging to different age groups.