5.The diarrheagenic E. coli can be differed from opportunistic E. coli by their: 1. antigenic structure 2. ability to utilize lactose 3. plasmids profile 4 motility

The correct answer is 1. antigenic structure.<br /><br />Diarrheagenic E. coli and opportunistic E. coli can be differentiated by their antigenic structure. Diarrheagenic E. coli strains possess specific virulence factors, such as enterotoxins, which are encoded by genes located in the plasmids. These virulence factors contribute to the pathogenicity of the bacteria and their ability to cause diarrhea. On the other hand, opportunistic E. coli strains do not possess these specific virulence factors and are typically harmless in healthy individuals. They may cause infections when the host's immune system is compromised or when they enter normally sterile body sites.