2009 Volume 13 Issue 1 Pages 19-20
We examined the dynamics of antibiotic resistance and pulsed-field gel electrophoresis (PFGE) patterns of E. coli isolates from health swine feces. Ten piglets were randomly chosen in each of 4 pig-raising farms. Feces were collected at the piglet stage, growing stage and at the finishing stage. Ten strains were isolated from each sample and isolates identified as E. coli were used for analysis. All the 553 strains, isolated at the piglet and growing stage of 3 farms, showed resistance against 2 to 9 antibiotics. Strains isolated at the finishing stage showed reduction of antibiotic resistance, and 70 of 294 strains showed susceptibility for all the 15 antibiotics tested. Similar reduction was observed in the remaining farm. However, in this farm, antibiotic susceptible strains were isolated from all stages, being 62 of 300 strains susceptible for all the antibiotics. The majority of strains showing the same antibiotic resistance pattern showed the same PFGE pattern, but also different PFGE patterns were found among those strains, even they have been isolated from the same animal.
These results demonstrated that, the E. coli strains of each farm might be originated from multiple sources, and, although a same strain could remain along the stages, changes of antibiotic resistance patterns and PFGE profiles occurred in a short time period. Thus, for monitoring systems related to food safety, analysis at the finishing stage seems the most recommended. Moreover, studies to elucidate the causes of changes in the E. coli strains of intestinal flora might be of great interest.
