The genomic characterization of the E. coli strain behind the outbreak in Germany led by University Münster's Helge Karch is now out in PLoS One. Karch's team used the Ion Torrent PGM platform to sequence the outbreak strain, which it then compared to historical strains. The researchers report that the outbreak strain is "unusual in several aspects" and present a model to show that two historical strains, enteroaggregative E. coli 55989 and enterohemorrhagic E. coli O104:H4, evolved from a common enterohemorrhagic E. coli O104:H4 ancestor. Then, as a result of a "stepwise gain and loss of chromosomal and plasmid-encoded virulence factors, a highly pathogenic hybrid of EAEC and EHEC emerged as the current outbreak clone," the researchers write. Study co-author Dag Harmsen tells Nature's News Blog that this work "represents the birth of a new discipline — prospective genomics epidemiology." Niyaz Ahmed, the paper's academic editor and a researcher at the University of Hyderabad in India, writes in a PLoS One blog post that the paper "has an important bearing on the new proposed field of 'epidemic forecasting.'"
However, Ahmed also notes one limitation of the study — "it is silent on the mechanistic details of 'adornment' of these bacteria with several layers of fitness," he says. "Multiple antibiotic resistance, acid tolerance, enteroaggregative capacity and shigatoxin production all bundled up in one 'naturally' chimeric strain in just 10 years is extremely dramatic! The pace of evolution of the German outbreak strains has surpassed even Helicobacter pylori."