Unclassified Escherichia coli serogroup OXI isolated from fatal diarrhea of rabbits.

An unclassified serogroup of Escherichia coli, OX1, was identified in 151 of 196 isolates from 20 rabbits affected with fatal diarrhea and four with no visible illness. No other known pathogenic bacteria or protozoa were isolated from these rabbits. Six strains of OX1 produced a positive reaction comparable to a known positive-reacting E. coli O26:K60 strain when injected into ligated intestinal loops of young rabbits.