Do all clinicaly isolated e.coli must be having plasmid?

Not all clinically isolated Escherichia coli (E. coli) strains possess plasmids. While many pathogenic strains, particularly those associated with virulence or antibiotic resistance, often carry plasmids, there are also strains without plasmids that can cause disease. Plasmids are more common in certain types of E. coli, such as those in the Enterobacteriaceae family, but they are not a universal feature of all isolates. Therefore, the presence of plasmids varies among different E. coli strains.