Clonal diversity and zoonotic potential of MDR <i>Escherichia coli</i> isolated from poultry at different age intervals

1. A pool of 480 E. coli isolates of poultry (broilers and ducks) representing different time intervals (0, 10, 20 and 30 days) was selected for ribotyping and used to determine polymorphism of 16-23S ribosomal RNA intergenic space. All the isolates were multidrug-resistant (MDR). 2. Out of these, 10 isolates were tested for MLST (MultiLocus Sequence Typing) among which novel allelic combinations and therefore new sequence types were identified in seven isolates. 3. This work showed the changes in E. coli strains structure at farm level and individual bird level in host species raised on organised farms with similar parental lineage and environmental housing. The statistical results showed that the structure of variation is very different by farm, supporting a strong effect of location, which confirms the temporal clustering. 4. There were significant differences between E. coli strains in chickens and ducks, indicating host specificity of the E. coli strains. 5. Some of the pathogenic E. coli strains found using MLST belonged to ST735, ST2796 and a pandemic clone ST752 of ST10 clonal complex. The results strongly suggested the clonal expansion and establishment of specific MDR clones that have zoonotic relevance.